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Hypomesus pretiosus: Its development and earlylife history

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These studies have been suggested by Dr. W. F. Thompson,
director of the -Softool of Fisheries.
Other people have, like­
wise, extended a helping hand during the period of study.
F. 1. Lynch has always been accommodating and helpful, and has
aided with the. manuscript.
.Through his kindness various equip­
ment and chemicals have always been extended gladly.
Dr. L.
B. Donaldson, on one occasion helped sake plankton tows and
loaned plankton nets end a Chase Jar for rearing' the young.
.Dr. ». fan Cleve formerly of the International Fisheries (torn*
mission, now chief of the Biological lesearoh Division of
California, kindly loaned a young fish net two'.feet in diameter.
Hr. M. B. Schaefer of the International Pacific Salmon Fisher­
ies Commission, kindly donated his collections of eggs end
larvae of smelt.
Hr* Aliya Seymour, likewise contributed his
collections of poet-larval and fingerling smelts.
Mr. E. A*
Dunlop, present Director of the International Fisheries Dorn-,
mission, allowed the writer the us© of his microscope in the
Mr. T. Half*on, a commercial seiner of Brown Point,
Utsal&ddy put his daily catches at ay disposal for the purpose
of measuring fish length and obtaining scale samples from same..
To all these men, the writer is indebted., and expresses
his thank® and sincere gratitude.
Last but not least, gratitude is acknowledged from the
University of the Philippines for its part Is sending the
writer to the University of Washington for: advenced. study.
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Fart I'* Introduction
Knowledge of Ilf® History ant Its fain®
The Problem 1
Systematise and Distribution
fart II* Methods and Materials
Fecundity Determination
Sources of Materials 'and MeansEmployed
... The Preparation of Materials
fart 111* Spawning and Spawning Season . .
Previous Investigations
topography of the Spawning Beaeh
Sexual ■Dimorphism
Sex Batin
Ovarian Ova
Spawning Activity
Spawning time and Hole of Physical Environment
Part XT, Six®, an# Age Composition
Sampling the Population
Size limits _
length Frequency Method of Age Determination
Brief Historical He view of the Seale Method
Assumptions Governing the Seale Method
Appearance of Scale on the Body
Shape of Scale Depends upon location onthe Body
Structural feature® of the Scale
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Formation of mrnll
A g r © f the Spawning Population
Pert ?. The Gonads and Ova
The Testes
The Ovaries :■
Fecundity /
later Absorption
Fart ?I. Morphology of the Smbryo
Embryonic Development
tart T O * Mechanics of- latching
Means of Sfttching :
Adaptation to Environment during Incubation
Hatching in Smelt
Fart fill* Smelt larvae. Postlarvae and Fingerlings
Materials on Sand
Stomach Gontest
Habits of larvae
The larvae
. 10#
' 10?
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M S f OF mi L i S
Table l. Statistic® of the eoomercisl landings
of smelt of the State of Washington fro® 1934
to 1940 iaeloeive.*
Table II* ©revel elses m
smelt* -:
the spawning bad of
fable ill.* The length fre%u©»oy distribution of
m a l t ®«fl®e of the spawning population.
fable If* Seale measurements..
samples of spawning fish.
fable V*
fable VI.
Seales taken tram
Variation la the length of the testes
Sgg count in @ female smelt
Table VII. Measurements of the diameters of the
> unfertilized ora of smelt
fable fill,*
of the diameters of
water-hardened ora of smalt
Map of Puget.Sound
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' IS
'l i s t of rxomass
figure 1* Graph of the tidal cycle at Maple
Grove (sum m r , 1940) show lag the time and
height of tide at spawning.
figure S. Graph of the length frequency dis­
tribution of the.spawning population of
figure'3* ‘ A'comoosit©'graph of both seres
constituting the spawning population of
Figure .4. Graphical representation of Lea’s
method of determining the fish length at
which the scales first appear on the body
by extrapolating the line of least squares
until it bisects the base line.
figure 5. Regenerated scale froma two-year
old female smelt (14.7 cm.). This is a
very common type of regenerated scale.
El times natural size.
Figure 6. A second type of regenerated scale
from a male yearling (12.8 cm.)• Hot
common. 21 times natural size,
. .
Figure 7. A third type of regenerated scale
from a male yearling (12.8 cm.). 21
times natural size.
Figure 8. Scale from a fingerllng smelt " •
(5.5 cm,). 21 times natural size.
Figure 9. A scale from a one-year old female
- smelt (11.6 cm.). 21 times .natural size.
Figure 10. A scale from a two-year old male
'smelt (14,7' cm.) showing one annulue*
Figure 11. A scale from a three-year old
■ female smelt (17.8 cm.) showing two annul1.
Figure 12. A photomicrograph of the cross
section of the ovary of the smelt showing ■
ova in various degrees of development.
52 times natural size.
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Figure 13.- A photomicrograph of the mlcropyle
of the w e l t egg... 136 times natural size.
Figure 14*. Sem i l a g r a a a 1 1c drawing of the
unfertilized egg of the smelt showing
'the mlcropyle and its relation"to the
germinal reside. Zona radiate externa
is shown la place prior to aversion. 61
times natural size.
Figure 15* Camera l u d d a tracing of the 2-cell
61 times natural size*
Figure 16. Camera luclda tracing of the 4-cell
61 times natural size.
Figure 17. Camera I n d i a tracing of the 8-ecll
' stage.
61 timee natural size*
Figure 18. Camera India'tracing of the 16-cell
61 time® natural size.
figure 19. camera I n d i a tracing of very late
segmentation {16 hours). 61 times natural ■
Figure 20. A photomicrograph of a sagittal
section of smelt egg, five hours after
fertilisation, showing the heginuiag of
the segmentation cavity. 136 timee. natural
size. •
. 79
■Figure 21. A photomicrograph of a sagittal
section, of an 18-hour embryo showing the
beginning of gaatrulation and the thicken­
ing of edges of the bl&stodise preparatory
to the formation of the germ ring. 136
times natural size.■
Figure £2. Camera l u d d a tracing of an l@-hour
embryo showing’the commencement of .the g e m
ring. 61 times natural size.
Figure 23. Camera ludda tracing of 23-hour
embryo showing the germ ring at the ■
equatorial plate, also the embryonic
shield with the embryo projected on it.
61 time® natural size.
Figure 24. ' Camera l u d d a tracing of a 39-hour'
embryo projected acres® the long axis of
the embryonic 'shield.' 61times natural size.
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Figure 25* Camera luclda tracing ©f a 50-hour
embryo showing the presea©® of lupffer*® ,
vesicle. 61 times natural size.
Figure 16. Camera luclda tracing of a 67-hour
embryo. Kupffer*s vesicle already gone.
61 times natural size.
Figure 27. Camera luclda tracing of a 72-hour
embryo with the tail freed from the yolk
for the first ti»e. 61 time# natural size.
Figure 28. Camara luclda tracing of a 97-hour
embryo showing the intestine approaching '
the proctodeeum. . 61 times natural size. >
Figure 29. Camera lucid® tracing of a 147-hour
embryo showing dev®loped intestine and the
characteristic pigmentation' on the ventral
side .from the yolk sac to the tall.region. '
61 times natural size.
Figure 30. Embryograph showing the development
of ova from the two-celled stage up to
hatching in relation to time of incubation
in terms of hours {number© in parenthesis),
Figure 31* Sewly hatched smelt larva,
size 3 mm.
Figure 82. five-day old smelt postlarva showing
large melaaophores. folk is fully absorbed*,
new set of melanophores la shown above the
intestine, natural size 6.5 mm.
Figure 33. Smelt postlarva shewing the. resorption
of the dorsal fin fold and the formation of
the dorsal and adipose fins; ventral and anal
fins are also advanced in development but.
ventral fin fold is still intact. Distribution
of pigment bodies is characteristic. Natural
size 17 mm.
Figure 34. . fingerling smelt. Melanophorea on
dorsal side are spreading' laterally, fish
is fast approaching adult configuration.
Natural size 85 mat.
Figure 35. Fingerling smelt older than the one
shown in.figure 54. Jfelanophores along
ventral side, of the body sunk deeper Into
the muscles, Natural size 45 mm.
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figure 36. Finger ling smelt.- Melaaophores ■■■ '
along lateral'line are advancing'anterior- ■
ly. Pigmentation on dorsal side more in­
tense than in any previous lengths, fiatural
sin© §1 ma*
figure'37. Pingerling smelt. Lateral mel&nophores formed a broad band along the
lateral line. Melaaophores on the dorsal
side have further spread downward, natural
size 68 mm.
figure 38. Fiagerllng smelt with full adult
pigmentation completed. Natural size 75 mm.
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m a u m
S i
'i w w n w a i m
M S f I*
Knowledge of Life History ant Its falue
One prerequisite of successful conservation Is, mo doubt
a sufficient knowledge of the character of the egg ant of the
life history of the species wished to be conserved.
adequate knowledge sight prove ©f incalculable value when one
Has to deal with pelagic eggs and larvae, which are caught
la the plankton met more often than the spawning fish.
a knowledge enabled Hjort to discover and localize a tremen­
dous fishing bank of Borweglaa cod hitherto unknown to the
fishermen of Morway.
As a consequence, the yield of the
fisheries was very materially augmented.
Basically, as cam fee gleaned trim- literature ©a life
history investigations, the success or failure, of the fish­
eries depends upon the success or failure of spawning, em­
bryonic development and the completion of all■larval stages,
at which periods greatest mortality, is supposed to eeeur*
That various authors recognize some such critical stage#
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in development that contribute to the success.or failure of
any o»® year’s output of fish Is well known, although there
Is so complete agreement as to wbiet phase is' the U f a
history of the fish,is the m m
critical,. SJorb (1914) is
of th® opinion., that tho critical period In th® life history
of th® daring the first feeding stages of the
young fish and. showed farther that a preponderant year class
can he obtained from poor spawning*
On the other hand,
Thompson {1019) expressed th# belief that in cockeye salmon
success of th® fisheries depends much acre on the number of
apumuNrr ©a "the ground than upon say other factor.
It Is
assumed here that the number of spawasrs represent the max*
Imum number a given ground earn maintain! any
spanner in excess ©f the maximum number would not materially
increase th® yield*
On the .Pacific coast of the Waited States, scant attemtion has been given studies on embryology, In spit® of the
extensive investigations in other fields of fisheries'bi­
Of the fait life histories known, th® salaonold group
has receives the greater amount of attention*
however, some attention has been given to other fishes (Thomp­
son and fas. clave, l§3§ on halibutf Wolford, 1032 on barra­
cuda; Clark,' 1913' on grunioa; Scofield, 1924 on sardine; Budd,
.1940 on six other Oaliforni® fishes, etc.).
The smelt (area—
ue ©retloans) is" holding it® own comm­
ercially and both fresh end f m m m fish find1a ready market.
Besides, it is popular caoag sports fishermen and, a®. Bigelow
end Welsh (1925) lave aptly remarked of th® Atlantic smelt,
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‘Which Is also true of the surf smelt of the Faelfie, *from
th© dollars ant-oasts standpoint, its sporting value to the
■ coastwise inhabitants is probably .greater* than its coim&erelal
The smelt being shore spawners, the commercial fish­
eries draw heavily.upon the spawning population and It ean
easily be subjected to very intense fishing*'
■ date, fable 1,:*show indications of fluctuating yield la the
: catch with probable overfishing,
Thus, a series ©f reseat
investigations has been carried on with emphasis on spawning
• habit®, fecundity*' and early life history*
the Problem
Mb early as 1881, th© smelt was observed spawning near
• the mouth of *Q,uill©hutew liver (now Qulllayute) by Swan*
Details of spawning habits, however, were not described and
observations *were rather casual.*
Many years.later Thompson
ant associates. {1936} made similar observations on the inter­
esting spawning habits of the same fish on the ©pen beaches
of the Olympic .Peninsula,, Washington about, the mouth &t Cedar
- Greek,
Detailed Information as to type of spawning bet, spawn­
ing habits, and fecundity were reported*
But the manner of
aetua.1 spawning was,.not ascertained because, of the roughness
of the surf and the rapidity with which the spawning act is
Loosanoff (1930) and Schaefer {1935} (both papers
appeared in 1936} mad® further investigations on the smelt in
the same locality (Ctsaladdy, Caaano.Ja,.}*
The latter mat#
a much more extensive study than any of the ..previous workers
on th® same problem,
Schaefer’s work Includes a racial snaly-
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sis and a statistical treatment of various biological phases
and ecological phenomena involved in the Ilfs history of th®
However, in mom . of the previous papers o n .1yp ome sus
gretlosus M s the embryonic, larval an# post-larval developmeat of th® species been studied to completion.
It la,-there­
fore * for the purpose', of filling this gap la the natural
history of the smelt ..that this research was attempted.
Systematica and Distribution
fhe surf smelt is closely -allied to the salmonoids, both
being isospondylous fishes, although th© former Is now allocat­
ed to th# family Osmeridae.
Jordan and Gilbert (1882) listed
■ *•.
it under Salaonidae, later on Jordan and Svermaaa (1896) and
Bigelow and Welsh {1925} under Argentlaltas* '
■ -Jordan (1923)
brought it up to- data under Osmeridae.
Bigelow and Welsh
speak of the®, as "small salmon in.- all essential respects,
except that the .stomach Is simply a sac with a few or no
pyloric--caeca, whereas in their large relatives, of the salmon ■
there are large numbers of such caeca*.
Samuels {1904) calls
them "second cousins to the graylings and trout".
In the, revision of th® Iforth Pacific os&erids, Bibbs
{1925} listed six genera with 11 species,
Th® .genera under
Osmeridae are. widely distributed, occurring particularly in
th® northern., latitudes of both the Pacific and Atlantic
basins, as well-as along the Arctic coasts of both oceans*
However, the species of Hypomesus are endemic to the north
Pacific ranging from Japan to San Francisco,
light species
of six genera of the- family Osmeridae occur on the ©oasts
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of ffasbington, Oregon and adjoining regions*
species of Hypomeeus —
fiere are two
g, olidus and H. oretloans.
former is anadromous and th® latter is a surf spawner.
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The field Investigations were carried on at Maple Grove,
Gamano Island*
Two summers (1939-40) were spent in the
collection of specimens for laboratory studies*
Spawners are
easily obtainable* not only because commercial fishing coin­
cides with the spawning season., but schools of Hynoaeaua
pretlosus spawn close to th© edge of th® beach.In water only
a few Inches deep,
this habit exposes than to very intense
fishing by hundreds of sport fishermen, who, though using
only ©.rude rakes, nevertheless fish effectively*. Samples
from the commercial catch and from raking were. used, la the
determination of the age compositlorn of the spawning popula­
Scales were removed from above the lateral line and
below the dorsal fin and were later mounted on slides la
water glass*
Fecundity Determination Fecundity'was determined on th© basis of ©gg counts per
From 474 fish only '8 females were suitable for
fecundity ..doteiainatien*
They were preserved In 4 per cent
The females were washed to remove excess formalin.
The fish were then cut open and the ova removed into a small
Th© excess water w«© then drawn off so that the eggs
were Just moist*
Weight of eggs was taken in grams on a
torsion balance accurate to 0*1 gram.
Th© average number of
eggs la a gram was multiplied by graa-weight of th® entire
mass of eggs to-obtain the total number of eggs per female.
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Sources of Materials and Means Employed
. dll ©ggs for incubation were artificially spawned and
.■fertilized from' smelts caught in-th® beach seine#
Th© eggs
were readily stripped from rip© females by alight pressure
applied by th® thumb and th® index finger upon the belly with
a rent-ward stroke starting from behind the base of the-.peetorsi fins,
ililt was removed as easily#
The. very adhesive
eggs and. milt were, mixed in a ..erystalll»bloii dish containing
a quantity of sand, and gravel and half-filled with water.
fertilization was completed immediately#- Excess milt was
washed off in several changes .of water and them- the eggs were
laid aside to water-hsrden*
At the completion of water ab­
sorption, the mixture of sand., gravel an#- adhesive., eggs was
bagged in cheese cloth, placed in a..wooden frame, IE x 6 x 1
inch with, a-wire, mesh bottom and covered with a second frame
©f the- same size and materials.
The. frame was buried la'the
spawning bed under 2 Inches -of sand and gravel for Incubat-toa
under the same conditions in which they are
The ova were submerged twice, daily for-two. or three
hours by the'high tides*
The length of. the incubation period
varies inversely-with the temperature$ higher temperatures
hasten, lower temperatures retard, development*
• Samples of developing eggs were taken at two-hour in­
tervals during-the first 8 hours after fertilizations twice
a day |morning and. afternoon) after-the first 8 hours -until
the- completion of th© day of incubation*
daily sampling was found sufficient until hatching tine* .
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Hggc were returned to the beach after' each sampling except
during the first 8 hours after Insemination.:
The rest of the ova were incubate to batch*
larvae were reared in a. abase Jar* . Half of the amount
■of'water in the jar was removed and changed two time® a day
to replenish the. oxygen supply*
This wa® easily done because
the fry while absorbing th# yolk stayed upon the upper surface■
'of the water, leaving the lower levels free where a rubber
siphon was.usually inserted to drain off the necessary amount
of water,
the siphon.
fresh sea water was introduced into, the jar through.,
To retain th® sea water at ita normal range of •
temperature, the jar was immersed in a five-gallon paint can
through which' passed '&;■constant stream of cool tap water*
This 'maintained a stream of circulating -water around the rear­
ing jar.
With such'a crude device,;the larva®, were reared with
difficulty is the field*
However, few larvae survived a
period of two weeks*. Morphologically, no outstanding changes
.hat taken place during this period*
Ho older larvae were ob­
tained^ ■ There Is evidence to lB.dica.te that, the critical period
in the life of'the young fish is between hatching and thetim®
it begins to feed.
This parallels th© history.of the herring
in which Bjort (.1914) found th# highest mortality occurring
during th© first .stages of feeding*
We were unable to determine.,
exactly th® type of organism utilised for food at this stags*
la th© rearing jar, a small amount of plankton was introduced
once a day after th© yolk had been fully absorbed by the larvae*
The concentrate consisted mainly of diatoms and minute crus-
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taeeans, mostly copepods*
It Is highly probable th© young fed
on some of the plankters because sew® of the. larvae survived
15 days*
stirring or aerating mechanism was unavailable ^
and the lack of adequate aeration no doubt contributed much t©
the high mortality of the young fish*
hive floating boxes had been tried. In' rearing th® young,
but naves shook the boxes and spilled.the water out with, the
larva®, which congregated on the surface layer during the peri­
od of yolk absorption* ■After a day or two all th© young were
lost Into the sea*
This method was then discarded as inap­
propriate under' the existing circumstances* "Perhaps a larger,
more elaborate, and more expensive cage .could 'be constructed
to suit conditions in th© locality*
In the hope of 'Supplementing the larval and post-larval ;
stages' obtained 'la rearing, a.number of surface and bottom
tows with a young, fishnet were made during'the. period of in­
vestigation* ''But no young' fls-h were caught*'
Plankton nets
were tried and surface tows yielded only newly ■hatched fry*,
feeing was undertaken luring high tit®.,.when- it i s 'believed ■
later ...stages might have been carried by th# incoming current
towards the shore but non© of these stages'were caught.
stages had been collected in the lower part', of .the Puget Sound,
particularly la th®'vicinity of th® month of Duwealsh liver
and about th© mouth of Puyallup liver by Hr* Seymour*
and descriptions of the later life history of th© smelt are
based on these collections*
As .many observations as possible were made on living
eggs; pertinent notes, were taken*
'Detail's,, however, were
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oosipletei in the laboratory fm m statue# sections, whole
mounts, and temporary mounts cleared in 10 per cent glycerine
In BQ per cent, alcohol.
The Preparation of Materials
In the preparation of specimen® for Mounting an# section*
lag, a number'Of fixatives have been employed*
Zenker’s fluid
was found' satisfactory in some cases but there was the"danger ■
of leaving traces of mercuric chloride in the'- tissue*
traces produce dark splotches .in- the- stained'..tissue and 'im­
pair the clearness of the sections"*'; Bonin’s ■fluid preserve# :
and fixes well and as a general fixative fop embryologlc&l
materials is superb and considered the safest fixing agent for
such Materials* ' It-la' convenient to use for' it gives excell­
ent results with nearly all stains*
It' should be remembered,
however, that yolky''materials are always., refractory.
should not toe taken as a oritlets* against the suitability of
Bouin’s fluid as, an almost all-round fixative*
"Susa*1 proves to toe particularly suited to yolky material® *
the yolk in eggs as well as the embryonic tissues cut well*
Galigher (19554) has'found it highly satisfactory where other
fixatives fall.
Presence of mercuric chloride In this reagent
Makes it necessary to remove' all traces of th© substance, other­
wise the stained sections will be marred by a dark precipitate.
All specimens for later studies were,kept indefinitely in
©0 per cent alcohol*
Iggs kept over a year In this, .grade of
alcohol, irrespective- of whether fixed in Zenker’s or Bouim’s
fluid, have bard and brittle yolks which cause difficulty in
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The yolk may drop at the time of sectioning or upon
the dissolution of the paraffin la xylol preparatory to stain­
Hewly fixed materials out better* but not when xylol,
has.been used'as a clearing agent.
Specimens embedded were
first tinged' with eosln or erythrosin*
This facilitated the
orientation in embedding and furthermore provided contrast
between the eggs and'the paraffin, otherwise the two are hard­
ly distinguishable one from another*
Th© egg shell was re*
moved or widely punctured to insure proper infiltration of
A number of clearing agents were employed.
Xylol which
rendered the eggs too hard, and brittle was entirely discarded*
Terpineol was tried' and gave a-good result in a number of
Specimens fixed' and preserved la th©' summer of- 1939
• were treated with 2 per cant phehol in 80 per cent ■alcohol for
a few hours with the hop© of rendering the yolky portion-soft
."enough for easier sectioning* but. th® desired result was not •
accomplished, probably because' of the employment of oarboxylol a® the clearing agent.
M ': : :
. -
Dioxan, a comparatively recent reagentia ®icrotechn.lque>
gave many good.'results*
It ha®, the distinct advantage of
greatly shortening', the whole process of paraffin embedding
because dioxan. happens to be perfectly miscibl© with water,
paraffin, alcohol, xylol, or even balsamj in addition, it is
a solvent for many common chemicals that are utilised as in­
gredients in fixatives, such as formalin, alcohol, picric
acid, and even mercuric chloride*
exercised in its use*
However, ©are should be
Fumes of Dioxan produce a toxic effect
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if a large enough/ftost is .Inhaled..
This. necessitates its
handling. under a hood of in a well Teatlisted room.
. Whole mounts ■and "sections of embryos in stages of de­
velopment beliyed necessary for this'study were made.
and S@lafi©M*i» haeaatoxylia were employed in the staining of
sections, with, trlosia'as a counters tain#
O ■■■
Whole mounts'
stained with either Harris’ fcaaaotoxyllfr or borax-cartain®
{lynch*s Method}, hut mostly with'the'latter, which gives a
distinct brilliant, clear, transparent red color.'’
All serial '.-sections mounted were coated with a permanent
thin film of celloidin obtained by seahtng the slides la a
I per cent celloidin! parts of ether and
absolute alcohol for a few seconds after.the paraffin had hemremoved by xylol and.the slides had been passed through ah*
solute alcohol.
If it is desired to remove the film of coll­
oid in in the final mount, the slides say. be passed through
absolute alcohol and ether-alcobol prior to clearing,
film over the sections function® In two ways:
1) It prevents
th® loss of a section or sections of th© series from the
slide while la th® process of dehydration and -chaining*
is doubly important la.embryologioal studies when every section
on the slide is essential.
2) It protects all sections against-
any undue sliding pressure' resulting from applying th® cover
slip on the slid® or against any undue handling of slides in
later studies.
R eproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Previous Investigations
Employing vertebral counts and differential growth rates
of various populations la th® area as criteria for racial
analysis, Schaefer {1936} case to th® conclusion that there
are Many distinct races of Hypomesus ©retlotus within the
Puget sound region*
The smelt, as a result of differentiation
into several races, spawn at different times of the year*
There Is an overlapping of seasons but not, however, in one
spawning area*
One race spawns from May 15 to October 15;
another from August 15 t© December 1; still another fro*
August 15 to March 1*
Although th® different races utilise
different spawning areas, the fish do not'spawn simultaneous*
ly on all the spawning beds*
Th® smelt breed practically the
year round at on® place or another 1® Puget Sound*
The comm*
ereial fishery depends almost wholly upon the spawning popula­
tion and since no reports ©a commercial landings are made for
‘the month of April, it is assumed that spawning- does not
occur in that month. ■ Ieoh beach may be utilised for periods
ranging from two to four months,
The locations of the spawn­
ing beaches are given on the accompanying map.
Only a few animals have habituated themselves to the
forces of the surf on sandy beaches.
Among these animals may
be mentioned Emerita. Blepharlpode*lealoes (anomurans), Slllaua
patula {razor clam), Jaatodytee {sand lanee).'Leureethee tenula
(grunion) and lypoaesua pretiosua {surf-smelt}.
These animals
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O O »-
s 9£8 Hbr-
ifE-^ ^i.nflW®<’y
|R » 1 1
F U C *
•t Sound^o«i^^Acli<ic*ot Wot*r»
ShowinQ th«
Spawning Grounds of
the Smtljf
Numbers t to 19.
bibited without pertdissiodreproduction pro 1
of the
are dependent upon the surf either partly or completely be­
cause they lire or spawn in it or derive protection there­
Some attention has been given the smelt, particularly
with regard to its habit of frequenting the surf none for
Earliest mention in literature was made by Swan
(1831), who gave the atm© surf-smelt to Hyoomeaus pretlosus
because he observed that tbejMeaae is..o&:.high.tide end schooled up in the surf as the waves broke ..ageism!.Jibe Jimnfth.
found the spawn adhering to the pebbles* .Very recently three
paper© on smelt have appeared describing their activities in­
cident to spawning, and parts of its life history {Thompson
et al, Loosemoff, and'Schaefer, 1938).
Thompson et al, observed smelt spawning on an ©pen beach
and found them..making an inshore migration for the purpose of
depositing the spawn*
This migration was perfectly synchro­
nized win time and character to tidal cycles as they affect
the beach*.
The physical conditions under which the smelt
spawn somewhat parallel those described earlier by Thompson
and Thompson (1919), and Clark (1925), for the grunion in
Loosanoff (1930), and Schaefer {1935), made
similar observations and studies on the same species of smeltf
in inland beaches of the Puget Sound (TTtsaladdy, Cemano Is­
land )«
Although the attending phenomena such as tide, surf,
wind, etc. effect the smelt similarly In the open and Inland
beaches, the magnitude of the force© in the open beach is
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vastly greater, particularly that of surf and wind.
ature c © M it loas 1m these two places are aot only different
from one another, but also vary la the ease locality fro®
time to time.
Schaefer found that neither fluctuations of
salinity nor pHs e em to affect the smelt *dvjtriftSy..jCB£J&ty
continue their, reproductive activities unhampered*
But compar­
ative studies of temperatures between shaded and unshaded,
beach in the spawning area led Schaefer to the .conclusion.**.*.
"that the effect of shade is a tendency to hold 'the
beach temperature at a m m nearly constant level**Continuing he said, "Thus the 'selection of a shaded
; area by spawning smelt is probably not fortuitous,
but is a definite adaptation for the benefit of the
developing ova* in the sinner months the selection
of shades, area is of importance to the welfare of
the .species. .In the winter months, when the sun­
shine is- not so Intense, such shading is not
necessary and beaches such as that on Sataish Is­
land and March Point which are totally exposed
are utilized".
Topography of the■Spawning leach "
In the summer of 1939 and part of 1940, another study
was mad© of the smelt with emphasis ©a development and life
The investigations were carried on at Maple ©rove.
The beach is on the.'northern end of Camano Island end- guard®
the southeast entrance to the Skagit Bey fro® Saratoga Passage.
Thus the beach faces'Slightly northwest to west.
Where the
smelt spawn, the beach is partially exposed to direct sunlight
only late in the morning ami completely exposed from aidafternoon to sundown.
The beach slopes down- gently into the sea.
A very high
bluff of-clay, overgrown with trees, rises abruptly from a
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point ©a tie beach between 11 and 12 feet above mean Ion
fhi® bluff screens the beach below almost wholly froa
the morning sun and thus provides shady spots for the spawn-
lag beds.
Completely'screened■off froa the east and the south, the
wind can only strike the beach from the north' or west, or in­
termediate points, in order to affect appreciably the magnitude
of the waves*
And because of the sheltered condition of the
Puget Sound area, the swift ocean tides are barred by land
masses froa reaching the Sound is full speed*
fhia factor to­
gether with the absence of appreciably strong winds probably
contributes greatly in the absence of large breakers in the
it naturally follows from this that area® of erosion
and areas of deposition, which are dependent upon the magni­
tude of wave action® hardly exist her© at all*
The spawning bed is a mixture of fine gravel and sand
with small pieces of clam shells*
It the level of mean low
eater, stones the else, of average apples or larger are found$
further down are large boulders overgrown with numerous barna­
cles and mussels*
On one shady, spot on the beach is a seepage
of fresh water that keeps the surrounding gravel bed moist
and cool.
Around this spot schools of smelt were frequently
seen milling.
Sice Composition of Sand and Gravel on 'Spawning Bed
It the recess ion..of..
the tide,'examination of the sub­
stratum reyeale.t,,..a...diatlact stratification ©f the beach with
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the finest grains of sand topmost and succeeded by larger,,and
larger particles below,*
Thus it is seen that water action
causes a sorting of 'materials on the beach*
Thompson {1936)
fro* an open.ocean beach, and Schaefer (1936) from an enclosed,
beach, sorted samples of sand and gravel from'the spawning
beds according' to sizes by sifting the® through Tyler Standart SereenjScalf^Cvide Thompson, p.: 166 and Schaefer, p. 4}*
The latter found that-■the sizes of gravel., in Puget Sound which
hat attached ova, are on the average, slightly larger than
those found by the- foraer•
' J
for purposes of 'further comparison with the previous
workers, we took a.number of samples of aand'aad gravel from
the spots chosen by the smelt for spawning* ■The samples were
size-screened through.the Tyler Standard Screen 'Scale*
result obtained by use of the Screen Seale is given in Table
11 in weights.'and percentages by weight*
Our. observation
showed that the ova were often encrusted upon gravel the size
This is about the same sizes of gravel with attached
egg reported previously far Puget Sound spawning areas.
ever, they are larger In the size than gravels reported froa
the ocean beach*
Gravel and sand retained by screens with 20
meshes to the Inch and upwards are fine in texture*
sizes generally go into temporary suspension in water during
the high tides when water is quite agitated.
Areas of ..only, fine grains of sand do not find much favor
w ith the spawnera.
The smelt choose areas.with an admixture
of fine sand and coarse, gravel ■so that after the tide has re-
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fable XX* .Size screened gravel from the s p a m *
lag bed of smelt at Maple Grove, If41
(Tyler Standard Screen Seale)$ weight
in g r e w aad percentage by weight re»
- tained by each sereeii.
Height of
Meshes to
the inch
Percentage of
If if
8* ft
185 ,1
in a
ff •»
ff* 4
18 *8
11# 4
m '
Hotel Sizes of gravel retained by screen with $
ah& 10 to the Inch are the sizes usually eueresied with
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ceded a. this layer of compact fine sand shields the ova fro*
the elements,
this choice is probably not accidental but
rather a deliberate adaptation to .git® the eggs protection,
It is known that a compact surface slows down excessite eveporation of the. moisture in the substratum which Is necessary for
the respiration of the developing embryos.
On the Other hand,
porosity in the 'layer, where the .spawn is- lodged (attained
through the loose imbrication of coarse gravel) -'facilitates a
freer circulation of air .needed for the exchange of gases be­
tween the developing egg® sad their environment. 'Apparently
physical factors have influenced, to a.large, degree, the
selection of'the spawning beaches.
. ■
-Sexual Dimorphism
The male'smelt art readily distinguished, fro* the females,
even when a school along the shore*
The males are
dull olive green-on the back while the females are bright
bottle green with a somewhat metallic sheen*. It will be
further noted that several external anatomical characters
easily differentiate the males froa the females.
are present la the- mala faut abaent in tha female.
Pearl organs,
however, the pearl organs la some cyprinlds and suckers, the
pearl organs la smelt are but minute wart-like, excrescences on
the sides of the body, sides and top of the head as well as on
the opercles and fins.
Without close examination they may
escape detection, , They are seasonal structures' present -only
during the breeding season and absent the rest of the year.
The abdominal color below the lateral band is yellowish silver
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in the males and pure silver white in the females.
The female
has a. greater body depth and thickness on account of-the dis­
tension of the belly produced by'the large amount of roe with­
in; in spent females the belly Is flaccid to the touch; that
of the male is firm under any conditions.
The length of the
pectoral fins-of the male-is slightly longer'than -that of the
Similar conditions had been noted'In capelin (Mallotus)
but the pectoral- fins of the male capelin are proportionately
much longer than that of the female (Bigelow and Welsh, 1925).
Furthermore the smelt, like the ombiotooids, has developed
spellings on either side of the anal fin and.the anus Is pro­
vided with wing-llke flaps of skia m
the sides;.these are
absent in the females.
Sen Sat 1@
The sex ratio in the spawners was sot determined.
from our observations there were always several males accom­
panying a single female*
This preponderance' -of -male smelt
over their females was first "noticed by Swan.. In 1881*
was -such -a preponderance that he had to say, *1 handled and
noticed a great m a y and cooked several dozens on two success­
ive days, but did not notice- a single female”.
From this he
concluded... ’’that the females had -first -coat and cast their
Subsequent studies show that males and females school
together and are not segregated as Swan’s conclusion clearly
Why sex rati© in Bvoosssus- oretlosua should doviat#
so such froa the ratio of 1:1 is not fully understood at
In Qaaerus eoerl&mua Masteraan '(1915) also found
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there were aor® males than there were females while la Lophlus
luapus, Fulton (1897) found a- sex ratio-of 100 male#' to only
■■.■8ft females,
■The type of disproportion in-sex;'ratio wherein
the.females outnumber the sale is also frequently recorded*
This was found in some',species of flatfishes --{Fulton, 1904,
.Iftmts-aan, 1918), and in plaice (Refford, 1909).
.author recognized a reversal in dominance from males to female#
.as -the-years went by, i.e., in youngest fish the males exceeded
the females (55 per cent of population) while la the oldest
; fish the male# constituted but 8 per cent of the population.
Some, years later, ■-Rest®rasa discussed the same phenomenon
when- he found that young smelt were largely males, decree#ing
in number but still in excess over the females up to tfco
thirl. year*
in the 'fourth year he found only females and
caught- no males.
Hren the human being' is not exempted from
\ the phenomenon. -In a rather .light vein, Holmes and Ck»ff
(1988) after extensive "studies on selective elimination of
males” had arrived-at t£e conclusion that
"all the facts point to the male as the frailer- max*
from the earliest -embryos la which distinction# of
the sex are -readily traced, through the precariou#
period of Infancy an# even to- advanced .year#,
natural .selection discriminates against man."
'In an attempt- to untangle the question of why males ar#
outnumbered, Seiser (1924 a & b) -suggested one or two reasons,
or rather causes.
Again we quote.'*.
"that males are constitutionally inferior as con­
cerns ability to survive th@ deleterious environ­
mental conditions. As a result of this differential
viability, the older populations of those group#
showed progressively increasing disproportion of
the sexes. Th* males were held therefore, to be
selectively eliminated#"
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Then in another passage he stated that longer 'life .among
the. females is Paused by a double number of the sex chromosomes
of the type XX (XTc^}•
it is thus traceable to the so-called
"factorial hypothesis of heredity*1*
Conversely he pointed out
that the birds where the male possesses a duplex sex-ehromosost©
of if i'VZ%)t it experiences a longer longevity.
■From these observations we gather the idea that sex ratio®
vary one way or the other -depending upon constitutional ability
't©'ward off unfavorable ecological factors to which the species
is exposed.
Sex ratios also depend upon 'the duplex' character
of the sex chromosomes of the two sexes', duplex ity favoring
greater survival*
Whether the disproportion of the sexes in the smelt is
explicable in ways cannot be said with, certainty*
other possible explanation 1© that an abnormal sex rati© is
perhaps an adaptive measure designed by nature t© maintain
the stocks because in spawning the females broadcast their
eggs indiscriminately*
'Such a habit is naturally wasteful' ©f
the male element and thus will require an extra large amount
of milt if a -very -high"percentage of impregnation is to be in­
A male certainly produces enough milt for the require­
ments of the female if ©viposltiom is localised as la salmon,
trout, bass,' etc. but in ©melt where no doubt wastage of milt
©.©curs, more is required as a compensatory measure.
Hence we
©am see the necessity of two or more male attendants to every
female so as to offset any wastage of milt*
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Ovarian Ova
la smelt several-sizes of ovarian ova in different degrees
of development are present#
Schaefer divided them Into' four
classes based on the diameter of tb© ova intoi
a)-" Smmatar©,
0 to 0.13 jhus’b) intermediate, 0.10 to 0*45 mm.; e) maturing,
over 0*40 mm*; d| rip®, 0.8S to 1*50 mm*, when the eggs are
free in the lumen of the' ovary*
S© also'succeeded in treeing
the■development of ova into maturity.
That- this feet is
quit*-common had already been recognized and. demonstrated la
various fishes by earlier and recent workers, 'In grunion,
Clark (1925) noted three groups of & m
in the ovary*
.-la January she found' immature eggs but 1st® la February, the
same group have transformed to the intermediate group leverage
size, 0,78 am,),
The ripe ova are produced in twe weeks and
thereafter in cycles of every two week periods., the rest of
the spawning season.' .Fulton (189?) recognized'two series of
ova in herring, smelt, sucker, catfish; three series in
gadoids, plaice, and turbot; fieibisch (1899) and Franz (1910)
on plaice; Mitchell (1918) ©a various species of cod, flounders,
herrings and dabs; Thompson (1917) and Kolloen (1954) on the
Pacific halibut; and laltt (1952) on haddock.
Spawning Activity
The spawning season in Maple ©roup-is froa Hey to October
with greatest'activity during the months' of June to September*
For the entire Puget Sound area spawning' is carried on almost
throughout the year, a habit that
been’.established also
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for the lurop©an.smelt (Osmerus eperlanus) (Bloch, If96 during
March; .Xarell,. 1836 August to May; Gunn lug ham, 1896 Mar eh,
April, and .Hay and Sketrcn, ..1895 March to April)* .'.©fevloitsly
thorO'is.aa. overlapping of th© spawning season of smelt in .
various localities .of.Xurope as there is in various parts of
the Fug©t Sound area.
■ ■Our observations .during■the summers of If39 and 194© a t ■
Maple Grove shows©.that July and August witnessed the greatest
reproductive activity, with diminishing intensity in September
and later* . On the' ocean beaches the period, reported is between
Say and September,, a tin®-well within that of Maple ©rove.
©alike the gruaioa, which takes advantage of only a part
of the tidal series but once a month (Thompson and Thompson,
1919} or fortnightly (Clark, 1925), the smelt take advantage
©f any favorable tides of the same series.
The smelt spawn
on the receding tide, 2 to 3 hours after tb© highest peak i s <
reached (see Fig. 1 on tidal cycle). • This observation is
diametrically at variance with that of loosanoff (1936) who
reported.that normal spawning took place-on. a rising tide.
'Although this occurs, it is the exception rather than th© norm
o f :spawning conduct*
Once in a while the smelt seem to be
confused and do. ©pawn on the flood tide.
©rev® often, speak of this phenomenon.
Inhabitants of Maple
In the summer of 194©
we observed on two occasions smelt ■spawning .on. th©' incoming
Curiously enough when the tide got beyond the favorable
area (with right,mixture of sand and gravel and on the'correct
level on the beach)■they <pdt the beach and■retire© to deeper
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It has been noted that la th© early run larg# male©
attend the females hut late la' th® season" the larg® males are
generally absent. 'fhey 'are supplanted by more satire hut
'■mailer males* ' It was-at this time of the see©©®:that a male
as ©mall as 8.1 ea* in standard length was ©aught*' 'It me®
found to he sexually mature.
Seales from this fish establish­
ed It to he /definitely a yearling.
It is probable though
that'this fish is a precocious.sal© because it was the'only
one out of © ter 300 spawning males*
Males of the same size
taken from other parts .of th® Puget Sound .area are immature.'
This seems t© occur occasionally among oemeride for Shrenbaum
(1894) encountered it also in the lib© Hirer smelt (tea®rue
eperlanus^ where a four inch smelt was sexually mature end ■
yet other specimen® of the say®© length were immature. ■
At high tide schools of saelt come along the shore stay­
ing in th© deeper waters some ten to twenty meters off the
They can be detected through their flippings on the
Those ready to spawn come close to the water*s edge
soon after the falling tide reaches the,right level on th#
The green ones.keep away.
Th® mature fish closely
approach th© shore in small groups milling as they go, some
may even accidentally jump onto the beach only to get back
into the water by rapid flapping*
Preparatory to actual spawning small schools swim rapidly
to and fro.
Item a female is sighted several males dart for­
ward two or more of which may flank the female ©a either side.
The others follow some distance behind in the manner of a
plane' squadron la flight formation.
Whil# swimming briskly
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the Teats of males and females are pressed together*
sexual products are ejected simultaneously, the act lasting but a-'-few-seconds,
After the spawning set the school may
break away or:--swim to deeper waters.
In the Norwegian smelt
{Qsmerus eperlanus) Johansen and lifting {19195 had-noted,
that the sales and females swim together- while spawning*
school is so packed-as merely t© appear-as If they were rubbing
their bodies together in order to deposit the ora*’
u*loa anA f,*»™ales spawn a number of times in succession
and single females require several tides to deposit all the,•
■rxpw eggs ah iiiwxr ovaries (Schaefer, 1936}*■■,. This- was dis-»
covered froa the eommerclal catches made on-a: day prior to any
spawning; a series of females grading from unspawned to-almost
completely spent was found.
Similar cases have been.found by
the writer in his investigations-,'
spawning period.
Thus there' is a protracted
This appears to be common to many fishes
with pelagic ova as well as to some fishes with demersal egga,
where th© ovaries mature a number of batches- of ova during on®
spawning season*
.pretlosus does not utilize the whole length of
th© beach for' spawning" but shows preferences for certain areas
of th® beach which.individuals -use over -and over again and
day' after day during the spawning season.
They may be drives
away temporarily by fishermen (rakers) but after a while cose
back to the selected spot.
The explanation is not hard to
The samples of gravel (Table II) from these patches
show a close correspondence to the size of the -gravel reported
by previous workers (Thompson, p, 1SS and Schaefer, p* 4),
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These Investigators pointed out that only. certain size®' of
gravel are found encrusted with eggs*
la our observations size
of gravel has guided the choice of the spawning location and
since certain favorable combinations ©f sizes'of gravel do ;
not occur contiguously along the shore the result' was the'
patchy spawning*' ■
.Iggs are simply broadcast over the.spawning bed in a way
similar to. the Mackinaw trout (Or Istlvomer). 'The latter,
however, spawn over rocky shoals some 77 to 9 0 'feet deep
fFlsh, 1932).
luropean smelt have a parallel habit*
ing to Bloch (179$) they lay their eggs on the bare, rock® with­
out'regard to their'fat® one* th© ova are deposited*.
The eaeit
eggs are heavier than water and so they soon settle-'down and
become attached by pedestal-like bases to gravel particles
which anchor them to th® bottom and prevent their being earried
about by the waves* .
Wave action agitate®' the' topmost layer of light fine
sand producing a temporary suspension of th© finer particles
in water* _ Consequently, tb® coarser grain® of gravel ar® un­
covered and become .available to th® ova for adhesion*
the recession of- th© tide and the resultant settliag of th©
sand on the gravel, th® eggs become buried from 2 to 4 inches
deep in the sand often much deeper after a large group of
tourists have swarmed over the beach*
On extremely calm days,
when tremendcue spawning may take place, ova are found on the
beech entirely exposed to the elements, owing to the absence
of the fin© sand suspension created only by the usual wav©
Such exposure subjects the ova to-the rigors of
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They may be smothered by tourists or become deslc-
cated beyond the limits of recovery especially when spawned
la the morning or early in the afternoon a® sometimes happens.
Spawning Time and. Hole of Physical Environment
A aeries of observations were made to determine whether
spawning may take place ©a any favorable tide irrespective of
the time of th® day,
ed (Fig, 1).
A graph was prepared and is here present-
The results show that more often spawning takes
place in the -afternoon and early evening tides.
decidedly preferred to the morning tides,
These are
Occasionally, as
has been noted already* spawning may take piece in the morning.
There are 3 aomlng® recorded with spawning activity; two of
them occurred before 8 a*m, end one between 9 end 18 a.m.
Spawning as late as 11 p,m, has been recorded (Schaefer, 1986),
An instance in our own record (July 22, 1939} shows the highest
tide of the day at 9:20 p,», at * 11 feet and the night we®
calm; inspection early the next morning disclosed numerous
ova on .the beach la late stages of cleavage a® revealed by
microscopic examination.
These finding# appear to be contrary
to what had been previously reported by other workers.
has been said that,,, "th© smelt is knowato run only during
the. day from May to September" {Thompson et al., 1936).
the ease of th® Atlantic smelt,, however, Kendall (1926) found
the run to take place only during the nights.
In a series of experiments conducted to determine the
effect of temperature upon the spawning population, Schaefer,
(1936) came to the conclusion that temperature'does not affect
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Aug. 4®
Sept. 1 4 - ,
N s noon;
Sme l t
€ a 3 morni r g-
6p= e v e n i n g .
10 o
to Q
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to o
tli# breed lag" smelt; neither do other observable hydrographical
But the Atlantic smelt seem different* for la a •
report {1918} by the eommlssioaer of Fish and Gas# of the
State of Massachusetts mention was mat© of th© Intimate rela­
tion between'the temperature' of the water and the'run of the
The size of the run fluctuated and was' very much in­
fluenced by sudden temperature changes and heavy downpours.
The report also states they moved only by nights.
in certain of the spawning aspects, the Pacific and th© Atlantic
species find a common' ground in that both have a preference
for the outgoing tide.
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Si 21 A ® AOS COMPG&fXO*
Sampling tb® Population
In order t© determine at what age tb® smelt'attain sexual
maturity and how many times they may spawn In the span of their
life, samples of the spawning population were taken.
eatehes# as well as catches fro® raking# contributed to- our
Making obviates gross errors in sampling b#eaus®
the regulation beach seine has 1 1/2 inch' mesh stretehed mansure and Its action Is tuite selective.
Th® rakes used at
Maple Grove operate on all sixes of the,smelt population and
therefor® ar® presumably absolutely aon-eeleotive.
not all sixes of smelt come close to th® beach.
A beach seine
Is necessary to sample the largest fish# which.are females,
and are comparatively a very small proportion, of the population,
^hus the two types of gear supplement each other,
fhe comm­
ercial gear operates only on sites of approximately 11.5 cm.
in length and upwards% below this sis® th® smelt escape through
the meshes of the seine.
Because of the supplementing action
of the two types of gear used in our sampling, the samples
can be regarded as representing a typical cross-section of the
Sampling was spread, over a period of two weeks, each day
a sufficient number of fish being takes as they appeared on
th® beach.
At the time of capture, .the standard length of
each fish was recorded and a sample of scales from each fish
was kept and later mounted la water glass oa a slide for study.
R eproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Sis© Limit©
The aiz® of our samples ranges from a minimum ©f 8,1cm.
to a maximum of If*8 cm. in standard length.
Since the samples
ar« regarded as a fairly typical cross-section of the popula*
.■ ties, it may also be concluded that extreme size limits of
mature smelt la nature approximate these sizes,
fable 1® of
Schaefer’s paper p. 31, which records the smallest specimen©
, .v et 9*0 to 9.8 cm. and the maximum et 18.0 to 18.3 cm. standard
: . length confirms our evidence.
Comparing the two extremes
■noted by Schaefer- and th© writer, th® difference is slightly
over on® centimeter is,: th® ©as© of th© lower.limit and about
'half a centimeter la, th© upper limit.
But in his Utaaladdy
Collection, the upper-limit in length coincided with our© .
(Maple Grove); th© lower limit differed by an amount equal
to about 1,0 cm,
froa these set© of observations, w© say in
general that mature Puget Sound smelt will vary In length
from 8.1 cm./to 18 cm. and In rare cases may exceed the
latter figure- by not mere than 2 cm.
Length Frequency Method of Age Determination
The use of length frequency for age determination in
fishes was initiated by Petersen (1892) in his work with
Zoaroes vivlnaraa.
Els records showed that his fish lengths
fluctuated around certain modes, which led him to deduce that
each major mod© represented a year group*
investigators have used th® method.
successfully to Cynoscloa regalia.
Since then various
Taylor (191C) applied It
Hubbs (1927) on Hotrods
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atherlnoides and Heliooerca incisor not only■ascertained the
age® of th® fish bat found also that the *two year-class
frequencies' coincided' with those whose age is determined from
th® scales*.
investigators of .-the .European plaice*. ■
notably fieincke {1905), showed that the ages determined by
the- frequency method and its resulting modes tallied with
ages ascertained from reading both tb© otoliths and scale®.of
the young fish.
la ffirooiie&us oretloaus we have farther con*
firmed this .method of age determination. '
fable III show® the frequency distribution of the males*
of the females * .and of both sexes put together.
It can b®
noted that there Is «. preponderance of the sales over the .
females in the ratio of almost 3:1* but th®'largest fish were
all females. 'Previous workers on the smelt also reported the
largest specimen®.to be females.
While th® ratio between the
sexes as here presented is inconclusive, yet it gives* to a
large degree, a fairly good idea of the sex composition of
the spawning stock,
-lepeated observations spawning
schools always show an excess of males ever females*
noff (1936) reported that in his samples.of 2280 smelts* 73.02
per cent were males and that early in the season 82 to 95 per
cent of th© fish caught were .males.,
further he claimed that
at the beginning of the run each school was composed of la- f
dividual® of th® same sex* the females appearing a few daye- \ J
earlier than the males.
Such condition had also been noted j
by Swan (1881)., But in cur investigation® w® did not find
this to be true... He Ither did Schaefer {1936).
This phenomenon '
is' also known in .-'.other fishes such as* for Instance* in and*
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table III.
length frequency distribution of t b * 1940 smelt
otd. length 1ft cm.
Olaes-Iater*®! ttid-point
@.1 *» 8,6
S.Q .
9.1 * 9.8
9.6 * 10.0
10.1 - 10•5
10.6 * 11.0
11.1 - 11.5
11.6 - 12.0
12*1 - 12.5
12.6 - 13.0
15.1 - 13.8
13.6 - 14.0
14.1 - 14.6
14.6 - 15.0
15.1 - 18.8
15.6 - 16.0
16.1 - 16.5
16*6 • 17,0
17.1 - 17.5
17.6 - 18.0
' 1.36
11.88 .
■ 14,85
1 '
34 (jc-fa
0 .;
1 62,%
1° ^
, 120
Both sexes
Hot®; Bomber of samples in the table represents 20 per
oeai of all flab measured (total sample 2370 fish.).
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minnows, the females ©f which likewise precede the males on
th# spawning ground.
By inspection ..of the length frequency curve (Fig# 2) two
distinct modes .are'recognized.
Ho specimens in the first
modal group exhibited rings ©a their scales, an evidence that!
rings ar© not formed during th# first winter' of life*
fish are yearling®, and include fish faints# between 11 and
13 cm., with a mode'at 12,3b e»«
A second .group of fish dis­
persed between 14 and. If cm., with a mod® at 14.85 cm., show
et least on® annulus In their scale®.
They ar# two years old
■or over.
, Th# two modal groups were distinct la both sexes end
belong to two classes, with the curve for th© females start­
ing far to the right of the males.
This indicates that the
males become sexually mature earlier than the females of the
same age group mad at smaller size, i*©., the males grow more
slowly than the females.
This tread is verified in the actual
scale study where the females were found to have a longevity
of 'three years, most probably a year longer than the male® because no males were found older than two years.
ly we can'say .the males spawn only two seasons whereas some
females are available" for spawning in the third and last' year
of life,
Loosanoff (1936) la referring to the above is of
the opinion that smelt spawn only once during their life ami
concluded that "absence of older fish among th® spawaers
favors the hypothesis that the life cycle of the surf smelt
is completed in two years".
Later Investigations clearly
showed that his hypothesis would not bear close scrutiny.
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Group 1
Group o
Group II
t ocotocotocotocotocotocotocotocDtoootoco
0 0 0 0 0 5 CD O
H rH
Length in cm.
Fig.2 - Length frequency of spawning
population of smelt, Maple Grove (Summer
of 1940, Aug. 5 - Sept. 14).
Group I
Group 0
Group R
in i o i o i D u 5 i o i n i n i n i o i o i n i o i o i n i o i o i f i i / 5 i o
0D C O O O O O H H W W t O t O ^ ^ l O i n c O C D C ^ t ^
»H rH rH rH rH rH rH rH rH rH rH rH rH rH rH rH
L e n g t h i n era.
Fig.3 - Graph of fig. 2, with the fre­
quencies of males and females combined.
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th© ©melt tfaer© are three generations betisea th© f m m % «»t
th© oldest adults observed in m j one year*
polygon an# seal© reading# confirm this*
Both th© frequency
Hence th® lif©' eycl©
Is completed la three yours* ia®teal; ©f ia two years,
In many
©po©toons .sexual maturity is attained towards th® ®'ad of th©
first year of life •
This ©tataasBt 1® based On observations
that many males were sexually mature at snail sixes*
their seals® shooed no ©annius present*
Fig* 3 I® a. composite graph of the frequencies of both
sexes* 'Sere a® In the separate frequency curves, two major
modes occur*
dm© Is located at approximately IB,35 cm.; the
other at 14,35 cm, showing that th© combined population 1st*,
tlcates the -atm© ages «s the separate sexes*
It can be re-'
garded therefore a® a good Index of ag© determination.
Hordqvist -(1910) found that Osmerus ©oarlanus spawned at
thft'snd© second year but most die -after 3 years of age*
Clark (1925) encountered conditions in grunlon paralleling
those existing, in the.
.Puget Sound smelt*
'In Labidesthee
©leeuluc* a fresh water Siberia®-fish, .the Ilf© cycle 1©
completed very definitely within the year*
Of this Babbs
(1931) has to say the following:
■.**wit breeds at th# age'of on© year sad probably
dies before -Its second winter, leaving th® young*
of«th©*y®ar as th® only link connectlag th© gen­
eration of on© year with that of th© next*’*
Fraser- (1915) noted ©.emus Indications that capelin (Maliotus
vlllosus) spawn when os® year old and perish after spawning*
To determine the significance of th® length-frequency
distribution* scales from samples were mounted In water glass
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Frcm these scales the
(0ireas©r**01@a.e3& water-glass method}.
absence or prtsence, end number of annul! were determined*
Interpretations, in terms of age in years.were duly made froa
■ ■' ■
the readings*- ■ ■
Brief Elstorleal Review of the Seale Method
"Although- scales hare been the- subject of much investiga­
tion especially in-'regard to' their morphology and mode of
development (Steenstrup, 1861; Mandl, 1989 Baudelot, 1873;
. Usatsch, 1890, etc*) It was not really until 1899 that Hoffbauer in'his- studies, on carp made the first serious appliestion of th® theory of age determination based on th# circuit*
H@ -was accurate up to 3 years of age*
But in older fish he-"
was doubtful because th® scales ©omit not be read with ease*.
Extensive reviews of literature are given by Thomson (1904},
■. ■■■
faylor (ISIS}1and Greaser (19£6)«
A very.recent, historical
review of the scale/method is. by Tan Oosten (1989) in his
studies of the. life history of lake Huron herring including
a critique of the scale theory.
Seales,''as' anatomical'structures that give the ag# of
fishes '(in some cases definitely and accurately;' in'©tiers
doubtfully, due to some confusion in the- interpretation of
■ ©hecks or malformation and anomalies in scale-'.feature#}- have
elicited great interest in various investigations,
lee (1980)
in.-a review of the different method# employed contributed
sigmlly to. the problem of age determination by us© of seal©#*
She presented various ©videae©'and mathematical tests from
which she reached th® following general conclusions;. In oer-
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tain fishes ©neb. as salaen and herring ege-eag bs determined
with a sosslde*ebl* degree of certainty; tbs reliability of
the results in the .youngest ago groups ..of other specie® as la
sod-and haMoch,-will .depend somewhat upon the plats., of -captaro.
■fboasoii flt©4)' believed- that asniill represent years of ■
Ilfs la tbs fish* ,AmtsaeB’s fIfIS)'.lisa that'tbs scales In­
dicated '•tbs. mtsoant of growth during each year of life of the
-flail" was enunciated by steehstiup eyes a# early as 1861,
w h m be stated that scales, except tbs placoid, which ere
deciduous, increased■.la siis as the fish Increased Ita slss
and that tbs increase continues. daring tbs duration o f .Ilfs*
Brows 11904) however, disagreed strenuously with-the theory,
that annul! Indicate years of life.
His objection was.based
on-., the-.belief that la gadoid®, scale® are-shed after spawning
; and.that eonceatric rings are not annual accretion®*
.1© dis­
covered that in a 3 year old cod haring. 80, .60,. and 90 cir­
cuit, the axtabsr.'dspsndsd on the M e a t ion of the scale on tbs
body* . for this m m m
be ©aid the netted Is invalid. .
Ai.suapt.ions Governing the Scale' Method
■In the us©'.of .scales m
criteria for measuring the annual
■ increment in length'end age of the fish,"...certain as sumpt ions
asst b© aade if.the seals theory Is t© fee'valid.
In.the words
sf fan oestsn- (1989) these mm%
a)*Tfcat the scales remain constant is number and
(retain their) identity throughout tbs life of
the fish .
fe)*That the annual issrsssnt in the length (or
some other dimension which -smst then be used) .
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■ Of the scale sain tains, throughout the Ilf# of
the fish, a constant rati© with the annual ineromeat in body length*
c)wfhat the
sane time
.cover able
ation and
amnnli arc formed .yearly and at tho '
each year lor that'some other dierelation-- exist® between their fora*
Increment of time}".
that certain basic principles should- be assumed is clear
enough If we take into consideration that scales. In fishes
may either be shed .naturally as in gadoids or removed accidentally*
Should the periodic'Shedding of scales be a regular
occurrence in'certain fishes, then the scales fro® such fishes
. cannot, under any circumstances, measure growth much less
their ages because succeeding scales, will be all regenerated.*
In the smelt there-are many regenerated scales (fig. S, 6, 7)
even, before they reach sexual maturity, but there is no evi­
dence that they shed their scales .periodically; numerous
original scales are also-found*
Loss of scales is very prob-
ably accidental because the scales are loosely held in the
scale pockets*
This Is shown by many of- the fish losing, many
scales even with careful, handling.
In spite of this loss and
the subs*%ue&t .growth -of new scales, our. age studies based on
'the number of annul! -la not prevented for the reason that
plenty of original scales are still to be found*
These scales
retain their, identity and are valid indices employable in age
determine tion*
*fl» £oei'W' regeneratedscales”'
’are :i»ver' lifce.,'tlie1
'foci' of" "
the original scales; regenerated foci ere either -oval,
ellipsoidal or even very irre-gular in formation; circull'in
regenerated scales may be very irregular in development and
follow no definite pattern*
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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
'types of regenerated ■am l m of ■■:
saolt*, All a r n l m 31. tines natural els®* ,
figure 5, Begeaerated eeale fro® a
too year a M feaala,(14*7 ea* J* This :la a cosaaoa type of regenerated eeala*
Figure 3* A aaoaad type of regea*
elated seal© fra® a aai® yearling
(13*8 ©a*}. Sot r@rj eomon.
Figure f*. a third type of regener*
atod scale. ' Sot o q m m NU
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Appearance of Scale on the Body
■ .
Fro® various sources., it is gathered that' scale's i® fish
generally begin to develop in the young fish when their sizes
range fro® 2 to 4 cm. , age not feeing taken into eonsiteration#
this size range was established on various species of'fish
fey a number of worker© on the subject among, whom may fee men­
tioned Bandelet (1673.) t Klaatsch (1890}, and Us sow (1897).
furthermore Tims (1966) recorded that the scale of Gadus callarias, appeared 'When the fish was 3 to 4
long while Seek
(ifId) found that in herring the scale did not develop until
a length of 4 cm. was attained*
Others like lecot (I960)
found the smallest specimens of Mugll with scales already
developed was 2.3 cm., in length, while Heave (1936) working
on a number of specie© of trout recorded'length® of 2.85 cm*
to 3i2 cm. at the time of the first appearance of the scales.
Huntsman (1918) working on the growth of scales found that In
the'Atlantic herring (Clupea hare aims) Escalation*', started
along the lateral'line.
The same Is true of the alewlf®
(Foaolofeus paeudoharenRus) where the scales started to appear
at about 2*8 cm. in length*
On the other hand, Vogt (1842) using the time, element as
the measure of appearance of the scale, discovered that in
salmon scales did not develop until after the flngerling. was
3 months old, at which age the fish were probably.4 cm* Is
length or mere.
An extreme css®, had. been reported os the eel
by Gemzoe (1916) whore the scales did not develop until the
fish was 2 years old.-
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la the absence of young finger!ings on which to deter­
mine the length'’when the scales are produced Lee '(Its©) pre­
sented a method based upon the relationship of the' fish 'length
to the length of its scale.
To find out how close this method
work# out in smelt*., scales from 202 fish were mounted end the
Taila* (lToa.-jSSm-J3£-£smL,tojm M
of **• »«ax« aloag th>
latero-aosterior rllne was measured»-wlth„.,the
resnectire length of 'the fish {Table If).
'Plotting, the scale
radius Con theordinate) against the measured length of the
fish {on the abscissa)-Fig, 4 is the result*- Fitting a line
of least squares a straight line graph is obtained, • Prolong­
ing the lower extremity of the curve by'.extrapolation, it
finally bisects the base line at 7,05'em**- the length of the
fish at which: it is said the scales, should appear on the shin*
eoapariscn of the theoretical length (7,05 cm.) of the young
fish when the scales first appear on the body and the observa­
tions on lengths (5.5 to §,5 cm.) from actual specimens, one
readily sees that the two length values' (theoretical and'
actual) come close enough*
Although the method is non® too
accurst®, still it gives & fair idea of the approximate length
of the fish when the scales appear*
The method may possibly
give better results in other fish,
Flngerliags collected in Fun® and Fuly were studied for
the determination of length at which the'scales t irst appear
on the surface of the. skin.
Examination of. ih© skin of
fingerllng smelt showed that the scales could, be freely scrap­
ed off the skin of fish of a length of S.les.; in seme cases
at only longer length, i.e., at 6,5 cm, . A scale from the
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3 *m
“ (n
I* .
O 03
w■"■ s.
O O O O O O O O O O O hM H M «H H
© © H «©
M+» « I
1Gwk»© » ©M WU
© m © © ft
M 4* © W «
M O t* I ©
o © o a
O* e f t K K t e e e K
© A MW
43 M -p © W
04 H H
w3 a
a ©•
<§ © S3 2 , ° ' *
© **
m mM m w
** © © 43 M"B‘*
w m ** ** «io
iOiotoeaiocoioHO'©' l < 4 t t © ® ® © 0
<#« H Ii ®4 es m to o» co to
* * • • • • • • • • * • • •
* ■»
<# <©■<©© © © © © © N c ^ o s a a a o O H r i
a I!
© a © ©
S g ^ ' 0 *0
* © °43 —
J 8 * # 4*
a « © © ©
© & ©W W
w m
m m
© ©
43 43 P% m
m • 4* M
u W g .43'43
•o) O
«© © M'*H . m
M M ©» M '1-4 ®
3 43
lOO© * * * * * * * • • • • • « • • • *
• • •© o H W 04©8S3 &>©•<# «3 «3 «0«©&* 0*«
i i i t i
t • » i t I i * i
i i » i t
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
ioioioioioiomifiioio loifliomioioiflifl torn
tocotocotocotocotoco to oo to co to oo to oo tooo
Standard Length of Fish (cm.)
Fig. 4 - Graphical representation of
Lee’s Method of determining fish length when
the scales first appear on the body by extra­
polating the line of 'least squares until it bi­
sects the base line (see text for explanation).
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
-§.& m * flagerliag is illustrated is. Fig* 8-*. 'It should b© re­
member©cl here, however, that-title observation is 'based 'on the
aatual appearance of the scales ©a the surface of the skin
and not on the cooaenceoent of the laying-'down of the first'
Undoubtedly, the scale aalagea Mist have bean in­
itiated long before these sizes ware reached. .'
I Shape of Scale Depends upem
location on the Body
The scales ia smelt are typically cycloid bat differ fro®
one'another from place to place on the body in both length
and shape..
Of this Bamtssiaa. (1918) said:
...*th@ simple variations la the rate of growth
of the parts of the scale are responsible for
the differences-in shape and pattern -of .scales
from different regions*1.
Scales in the'anterior region of the body have their dorsoventral axis longer than the antero-posterior axis but the
reverse holds true of the scales in the posterior region of thw
body. In general It can be said that the length of the dorseventral axis.of the scales progressively diminish posteriorly
on the body.'
The antero-pos terior -axis is longest at the
region of the caudal peduncle, i.e., the length" of the- antero­
posterior axis exceeds that of the dorso-ventral axis*
Bush a
change is the relationship of the two axes results in the
dissimilar morphology of the scales.
Again, dorsal and ventral
borders are distinct one from the other.
Scales above the
lateral line have their ventral borders truncate (squarish)
ami broader than the more rounded narrower dorsal edges.
the lateral line, the dorsal border of the scales becomes
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broader and. squarish* the ventral borderof .same 1® narrower
and more rounded*.
fypic&l seal#® in the smelt would 'be the rows of scales^
on* or .immediately above or below* the lateral, line in the
region of,the body bounded by the tips of both the pectoral
and pelvic fins*
These scales {if no shedding has taken
place) would* at. the same time, represent the oldest scales
la the body of the fish*
At this region of the body of the smelt, the length of ..
the dorse-ventral axis of the scale is about equal to that of
the aatero-posterior axis and the scales are, more or less
Hence in studies of growth rate based on the
relationship of scale length to holy length, scales taken from
the spot located above would, be about ideal because they tend...
to vary less from each other in proportion than they would
were they to be random on various parts of the body.
Structural Features of the Scale ■
The typical scale has an eccentric center, the focus.
This area (nearer the,anterior end of the'scale) Is the oldest
part of the scale, around which the eircull are laid.
The .
scale' can be roughly divided 'into four areas employing the ■
focus as the reference.point.
These are the anterior and
.posterior areas respectively in front of and behind the refer*'
©nee point and separated from each other b y .wedge-shaped
lateral areas - the dorsal and ventral.
The area®, are distinct
and can be delimlted^from one another by .four imaginary lines
drawn through the angular bending of the- eireuli and radiating.
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from the focus 'towards- the' aotero-lateral and postero-lateral
borders (see'fig.'10),
The posterior:division of the scale
is the most'exteasire of the four areas sat at the same time
the easiest to' read*.■ ' Under the binocular microscope the scale exhibits' circuit
in bold relief upon a plain matrix*' The circuit start fro*
the focus and go towards the periphery of the scale in a rather
strongly eccentric fashion*
Sastsman (1913) recognized on
Osmerus eperlanus three types of ctreuli in the scales, vis,;
1)'spiral, starting from the center and."going around ia spirals;
a) concentric; 3}--bilateral (horse-shoe shaped), which are in­
complete c'irculi'situated about the periphery of the.scale.
Ih. surf smelt only two of.these types of eirculi are found,
;the. spiral tjpe being .absent. ' The bilateral, type is, accord­
ing to Masteman 11913) .and lee (1930). characteristic 'of.
winter growth while the.concentric lines, that of summer
growth* ■ According to- lee the bilateral lines., besides being
prominent in smelt and eel (Anguilla) are'also- very easily
trace-able .in salmon where they 'fora "the so-called •shoulder*
of certain winter rings,- notably the second in the sea".
The circuit., theoretically as'many in a m b e r as those
ia other areas, are very crowded ia the anterior area and are
reed■with difficulty or uncertainty in some fishes but -with
ease la'others*' -'The. .lateral areas have- the fewest number of
clrcull on account of the fact that they are .set'much farther
apart than in^either -anterior or posterior areas.
The post­
erior segment of the scale of the smelt is the region where
the age determination is made,
In other'fishes the scale
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markings are better read from the anterior field; la still
other fishes (herring, trout, salmon) the posterior field of
the seals is incompletely sculptured*
distinct zones*
The circuli form two
In one they lie ia a regular well spaced
interval and la the other are closely crowded.and irregular
(figs* 10 ana 11).
According to our conception of the scale*
the tone with well spaced .circuit would represent the period
of growth;. ■the zone with crowded circuli the period of re­
tardation of growth, which occurs, usually during winter but
may be produced ia other season© such as during the spring
migration in .Mugil (facet* 1930), or soon after summer spawn*
lag as in graaloa (Clark, 1935).
The area enclosed by the
first zone of crowded circuli or the area between any two of
these zones would.represent the total growth.of the fish for
any on® year of life.
The number of zones *1, represents
the age of the fish* ■These structural features of the scale
give a reliable the later life history of the fish aa
has been shown, for instance in the lake herring (fan Oosten,
While regenerated scales lose any resemblance to the
original scales, so far as the focus la concerned, they develop
circuli, and ia some cases even show winter ring (Fig* 4).
Regenerated scales have a much larger, oval or ellipsoidal
focus, which is never found la the original seal® (vide Fig. 4).
This oval focus has also been shown ia regenerated■scales of
fuadulas heteroolltus (Scott, ItlR), Heave (193©) on goldfish
iSarasslus auratus) showed that not only is the focus deformed
but that the regenerated scale is often polycestri® (see Figs.
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6 and 7 ) .
Studies on from 202 smelts showed that la spit#
of the presence of many regenerated scales, there were'yet
numerous scales on each fish at the time of capture that re* ;
tained, not only the original foci hut also distinctive fea­
tures that were well defined and easy to'read,
That original
scales are retained,, is indicated hy scale measurements (Table
The table shows that for any given length of the fish
there Is a corresponding length of the scale and that as the
fish increases its length, a proportionate accretion la scale
length is, likewise* added.
According to lee (1920) this
should not be the ease but what should be proportional to each
other is "only the increment in growth of each ia the same
Saving shown that the scales of smelt fulfill the
assumptions postulated by fan Oosten (1929), we feel safe In
employing the scales-as Indices to age.
Formation of Annul!
We have no direct evidence as to the precise season at
which the annulus is formed.
Samples at hand were collected
during the mating season and scales show no spawning nor
summer marls.
Only comparison of monthly samples throughout
the year which we did not have, would, establish, the precise
time of the year when retardation* of growth commences and
a term is preferred "¥o cessation' or arrest,'’because growth
still continues as evidenced by the deposition of circuli,
though the pace is slower, irregular, or erratic.
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when rapid growth is resumed.
Our evidence is indirect since
we hare found no annulus formed during the spawning season.
'All' annuli found are some distance away from the rim of the
scales examined {see figs* 10 and 111-.
Mo Irregularity or
sign of■approximation ia the format lea of the circuli has been
seen along the margin.or any of the scales analysed*
shows plainly that a© spawning cheek is produced in the scale
of our fish nor retardation of growth during spawning season.
Hence normal growth., can safely he supposed to go on in spit©
of the spawning activity of the fish,
This instance is very ’
unlike that of the grunion where growth retardation takes
place during spawning season {May to July) with the consequent
formation of a breeding annulus during that time or soon after;
winter rings are absent which indicate that they continue to
grow through.winter {Clark, lilf).
loosanoff {1936}, after studying monthly samples of the
Htsaladdy smelt, concluded that the annulus is developed la
the scale during the second winter of life.
His conclusion
is■supported by our frequency distribution {Table III) where
specimens about the first mode do not show any annulus in
■their scales.
The present writer agrees with this view for it
is highly improbable that the smelt, with a protracted breed­
ing and spawning season in summer, should have scales in the
first winter*
At best 'the smelt larvae hatched In the early
part of the season can have the focus of the. scale laid down
.and the scales then would still be embedded in the skin*
Those that hatch late in the season would likely pass their
first winter with only the scale anlagen present.
This la our
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iW F t P
* ontorlor field of ooolo
. *
of th© seal©
I*. ■
* lateral ftelde of ih® seal®
* posterior field of the seal®
an • first ammliio
» m m m &
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Photomicrograph of the phylogenetic
scales from different age group© of Smelt,
scales are 21 times natural alze.
figure ». Seale from a one
year old female smelt (11.6
©*»)« •.
Figure 10, Seale from a two year' old male'
smelt (14,7 esu) showing one annulus,
Figure 11* Seale from a three year old
female smelt (17.8 cm.) showing two annuli.
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surmise; only actual studies of fry ia their first winter
(which we do not here) can prove or disprove it.
the -work, of Keek .11916} may support our. assumptions*.
He ob­
served that for herring spawning in August,'' the.first annulus
is yet unrecorded on their scales after the--first winter of
Ufa., Molander (1918) noted that herring-.born-in the spring:
and early fall registered an annulus-after the-first winter,
although he found as well that herring'born during the period
from October to November did not'- show the 'first annulus until
after the second winter.
Age of the Spawning Population
in the previous discussion of length frequency distribu­
tion, it has been pointed out that there were two distinct
It has been shown further that the, curve for the com­
bined sexes is similar to either graph of the Separate sexes
la .having two-modal classes-,
.fT-oa these frequent lea the con­
clusion reached was that, at least, there were two year class­
es in. the- population," with a possible existence of -another
ysar class ia Group II.
Th© samples -of the spawning population, were analysed as
to- ages.
The smallest mature ©pawning individual -©aught ia
the rake was 8*1 cm. and-was a male, while the largest was
If,8 cm, and was a female obtained from'the commercial eateh*
The former (8.1 cm.) length is extremely rare,
The majority
-of the spawning' stock had but one annulus in their scales and
.are interpreted to be two year old individuals. -At a length
of -13.75 cm. five' fish out of seven have one aanuius in the
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The other two to act have any aasulu# at .all*
length agree® very well'with the lowest point between the two
modes'In the frequency polygon (Fig, Z}»
Since the two in­
dividuals ted not formed the first annulus. It would seem
that this length, would he the critical transition between the
zero Group and ©roup I*
This Is to say that- all specimens
having a length below 13,76 cm, will sot and ia fast did set
have any annulus at alls those at this .length pay or may not
have an annulus but most likely will have one; those above,
will surely have cm®,
five females and. no males were obtained
which exceed a length of 17 cm, and all have-two annul! in
their scales.
'These are doubtless Group*-TT. smelt and are
therefore"3 year old Individuals.
A fish of 16,25 ©a, shows.,
also two annul!, Apparently this is a, discrepancy, but .
actually it Is'.not, because- the fish is really .3 years old, .
but; stunted in growth#. Moreover other specimens of the same
length or longer do not have two asauli ia the scales.
we say our population of smelt consists of. 3 Group# - 0, I,
Translated into:terms'of years this.division means that
there are 1(42*7 per .cent ), 2(64*4 per cent), and 3(2.9 per
cent) year old' ©pawners., with the two year fish dominant in
number and the three year ©Id the least ©f the three groups.
This finding fits well and coincides with-the length frequency
It has been pointed out before (Loosanoff, 1936) that
the smelt spawn only once, at most twice, ia their life time,
with spawning- stock composed mostly of the two year old class
end that spawning takes place in the second year of lifej
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furthermore, that they die ia their third'year*
Oar'data ©a
/ Hypoaesus pretlosus do not agree with the findings ©f Loosaaoff*
However, it is easy to conceive with .him that most of
/ the Group II smelt die in their thirl year of life*
less it la incorrect to state that, the smelt spawn only in
their second, year of life sal die- in their thirl year*. . This
la. contrary to what ia recorded here.
There are three year..
\ .oil in the population as well which was confirmed
■ '
by Schaefer (1936) as well as Is the present studies.
Many males attain sexual maturity within'one year of
/ birth so.that, in the next spawning season, the young bora the
V preceding summer, will join the spawning population ia the
\ later part of■the season.
This is borne out by the.observe-
. ^ tloa that ia the rua during the beginning of the breeding sea\
son, large-sized males go with the run; as the. season wears
. on to e close only small males, which undoubtedly are just
approaching their second fall, are seen milling with the
This phenomenon is well the tourists and
fishermen alike.
So four-year-old fish have been found.. Longevity.1®
three years.
Why it should be this instead ©f longer is not
quite understood but Clerk {19S5) offered two possible ex- .
planations in the case of grmnlon. Basely that.either all fish
Eventually got caught in the fisheries In their third year or
they tie after the.third ©pawning season*' .
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BMMf ?.
the m i m m asp ofa
The Teetee
The smelt has a very asymmetrical pair of; testes, the
left member being extremely balky and several times larger
and longer than the right testis.
It extends anteriorly very
elose to the heart and partly envelope' the.anterior portionof the digestive traetf in torn its eepbalio end ia partially
'hidden by the lobes ©f the liver.
The right testis is club-
shaped and,lies' in a groove along the caudal portion of the'
left testis.
The teste® are white ia color while the ovaries
are slightly yellowish,
Kendall (1926) in his studies of the
American smelts noted, likewise, the great asymmetry existing
between the two members of the gonads ia both'sexes, the left
in both sexes being the larger, similar to the conditions '
found ia Hypoaesus pretiosus. ■
The length' of the testes has a. tendency to increase with
the length of the fish,with a possible seasonal variation
of volume in"the same Individual as has been known to occur
ia the top-slnnoW'(Kuntz, 'IflS and Geiser, 1924).
Based on
percentage variation from the mean, the right.testis'seems to
be the more nearly constant in size.
But when one individual
is compared with another whose left testis is approximately
of the same -length, the
right testis is-seen to bo much more
variable in length.By noting Tabl® ?
©an be cited.
cases nos, 5 and 10
The loft testis in both have the same length
but the right testis
of fish no, 10 is shorter" than the' right
testis of fish no. 3
by 31,2 par 'cent.
Other cases can 'be'
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Table ?. Showing the variations in the length of
■■ the teatee ia' eentlaetes1 and in pereentage deviation© froc. the m m m -length.
M&m'&£ Std.Length Lft.Testls JfiDaviatioA
of fishiest. )■ {■©«.)
from mmrnn
12.f ■
14.4 '
IS. 7
14.7 ■
. 4.0
' 8.7
-Si. 7
-it, 6
Rgt.Testls .^Deviation
from mean
1.8 1,9..'
" 1.6
2,3 S. 7
. -20.3
. -25,5
-5.8 .
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picked out from the table which show stellar differences,
fhis variation in the size of the testes ie of importance to
the fish because the amount of milt produced fluctuates with
the fluctuation in the site of the testes and high percentage
Of'impregnation of ova'depends, la turn, upon the amount of
milt available.'
Sections of the testes taken from spawning fish show a
very peculiar condition, unique for a fish having, a protracted
breeding season,;
In the lumen of the seminiferous tubules are
found practically nothing but spermatids and spermatozoa with
a greater preponderance of spermatid*;
This condition accord­
ing to Geiser (1934) was also true in Gambusia especially dur­
ing the copulation .season {August and September),
cells may be recognized bat the germinal epithelium ■is prac­
tically devoid of spermatogonia.
Active spermatogenesis is at
a stand-still, a condition often met with, only'' in animals that
have but a very short-spawning period,
The Ovaries
the ovary is a large organ and. during the breeding season
it occupies practically the whole body cavity.
Like the teste*
the ovaries are very asymmetrical, the left being very much
the bulkier and the right practically reduced to insignificance
and' situated very close to the vent, " This ovarian asymmetry
is also known in other fishes,
Heibisch (1899) observed In
plaice that the ovary belonging to the eyed side is bigger
than the one on the blind side.■ Even in viviparous fish
asymmetry ha® been found.
Euntz (1913) discovered is Gambusia
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afflnis that the ©vary on the left aid©'is always shorter than
th®' ©a® on the right* which h© explained as due to the inter­
ference of the stomach.
Again Han® (1903) recognized in the
viviparous blind fishes (Luoifuga and Stygicola) a' 'frequent
ilscrepaaey in the size of the ovaries.
The great''reduction
in-the size of/the right ©vary in. smelt is ■not confined to ■ . ,
this species alone because Byder '(1885) found an unpaired
©vary in ■.Ooabunla patruelis.
Svea in the .higher vertebrate#,
notably the birds, only ©a© ovary is functional end the'Other
is vestigial.
In th®:viviparous blenaies (Zo&rce#) the paired
embryonic primordial ovaries have fused together so that the
■adfilb 'has only a single bag-shaped ©vary (Wallace, 1903}.
■The ovaries, suspended I n a a®mbpan#\f romthe ventral side
O f the awiia-bladder, consist ©f a' large' number" of transverse
folds arranged in a; series.
In'the' folds of the ©vary'are em­
bedded and'nourished a large'number of eggs of varying sites
from the most.immature to ripe.
Sip© eggs are located at the
-caudal end of the ovary ant. in several layer#..
As a batch of
ova matures and fells into the lumen of the ovary, new batches
of younger eggs approach maturity.
Hence a longitudinal section
of the ovary will disclose, the presence of eggs in various :
degrees of maturity (Fig. 18).
This Is also true im/grualoa
as has been found by Clark (1925).
Schaefer (1936)", who measur­
ed ovarian eggs in smelt asserted on the basis of his statistic­
al analysis, .that a single female matures a number of batches
during on© season and requires several spawning'-operations to
deposit completely a single batch of ova.
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* egg shell or
* micropyle
s o m
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r J)j|
figure 1Zm A photomicrograph of the cross
section of the ovary of t h e .smelt showing ova ia
various degrees of development. 5£ times natural
Figure 13, A photomicrograph of the mloropyle of' the smelt egg* 13$ times natural si**.
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Earliest work on egg production among fishes w a s 'credited
t o 'Earner (I?&?).,
H® made'©ounts of the eggs' of herring,
smelt, carp and mackerel and even of crustaceans such as lob­
ster, shrimps and crabs.■ Very such later others followed*
among them were Blending (1841) on striped bass (Labrar 11beatus), larll {1880} on gadoids and Bunn (1884) on two species
of cod ( pollaehlus and G»_ virens|.
Although these men
made counts, their efforts did not go beyond mere ova enumer­
At the turn of the new century more serious attention
has been given to ova.
The researches of Reibisch (1899) oa­
th© egg production of plaice, where for the first time he
clearly recognized the biological importance of fecundity,
aot only for the welfare of the species but its relationship
as well to both size and age of the fish, gave new impetus
in this field*. 'Consequently interest had been diverted to­
other fishes and other workers appeared.on the seen©*
them say be mentioned Fulton (1890) on 39 species ©f marine
fishes; Franz {1910). os plaice, Thompson (191?) on Pacific
halibut, Mitchell (1913) on fifty species of teleosta, and
very recently Clark (1985) on gruaioa, laitt (1932) on haddock
and iiolloen (1934)-on the Pacific halibut*
That the size and age of the fish influence the number.
of eggs that may be produced is now well borne out by facta
gathered from various investigator®.
Reibiseh (1899) .con­
cluded, his studies on plaice by believing in the dependence
of the numbers of eggs on the age of the fish, and that older
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pLftiee produce more eggs then younger ones of the same size.
This was confirmed by the findings of Franz (191#) who said
that egg count in fish of the same length was greater in the
older one, and that longer fish of the same species produce
more eggs than shorter ones.
Iren In the viviparous Sambasla.
according to luatz (1913), brood production Is larger in the
larger females.
In the European smelt, Saltt (18f§) found a female 2© cm* .
in length carrying 86,000 t© §0,000 eggs whila lather (1@8§)
reported the tremendous egg production in American smelt'of
30,000 to 60,000;depending upon the sizci.
Many other fishes have also bees shown to produce more,
eggs, not only with Increasing size and age, but with inereas­
ing weight.
'This was shown la haddock, flounder, and cod
(Mitchell, 1913)I laitt (1982) proved it is haddock, and
Eolloen (1934) expressed the relationship of productiveness
to weight as a power,greater than. 1 (l**^8 ) in 'halibut (lippojjlossus), i.e., productiveness increases slightly faster than,
the increase "in weight; Fulton (1890) found the same thing la
another halibut (Hippoglossus vulgaris)*
Fecundity In the smelt has been studied previously*
gala we refer to Thompson and associates, Schaefer and loosaaoff.
From their counts, there was no doubt that the number
of eggs produced is directly proportiomal to the size of the
fish, I.e., the larger fish delivers more ova than a fish ©f
smaller size.
Xisselviteh (1923) on the Volga Caspian herring
and Clark (1925) e». grmsioa expressed this relationship as
proportional to the square of the length while Mitchell (1918)
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Is of the opinion that fecundity increases as the cube of the
Raitt (1932) disagreed with them, and,said that the'
fecundity increases by a power greater then 3, that is, an .
exponential relationship of the type F * CL where n is great-*
er than 3.
This latter relationship is further- supported by.,
figures on halibut (Kolloe-n, 1934).
In smelt Schaefer went
one step further by stating that the larger fish also;tend t#
produce' larger eggs but holds that the exponential relation*
ship F * CLn probably does not apply to the-smelt for the- v
reason that plotting the log of fecundity -against the log of ■
the length of the fish- did not show a straight line tendency
(see his. paper, fig. 16).
From our collection of .four hundred smelt.preserved, in
4 per cent formalin, only eight happened, to be usable females, j
and some of these were partially o-r almost spent.
To deter­
mine how many eggs each carries, the abdomen was slit open
and the ova emptied into a dish, washed and drained well so
that the eggs were just moist and free from excess water as
far as possible.
Then the eggs were grams -on a
torsion balance and count per gram from each fish was mad®-.
The average number,of eggs was used in the calculated count.
The result is shown in Table TI.
The ripe smelt egg is spherical, psraffin*like in opaque­
ness and composed nf big vitellus provided with numerous oil
globules, which are disposed around and close to the periphery.
A thin transparent yolk membrane holds together the yolk
granules and maintains the globular shape of the yolk mass,
©sternal to this membrane is another rather tough, somewhat
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Table ?I.
Std. length
(cm. |
Bgg counts in 8 female smelts
eggs (go)
per m
Calculated const
beset os eve. a© •
m m
sot speat ,
sot speat^
■ 1854
■ 81169
mot speat
sot speat
almost > speat
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elastic membrane, the egg shell or chorion.
Between the egg
.shell-and the vitelline membrane is the perivitelline space
filled with perivitelline fluid.
Although the yolk'la capable
of rotating within the -shell., still it does not generally do
*o sad the germinal vesicle {circular clear area -of proto­
plasm devoid, of oil droplets) lies close to the aieropyl®, an
opening in the chorion through which the sperm cell enters the
The animal pole of the egg lies. near.the mieropyl®}
the vegetative pole lies farthest from the aicropyle,
the salmon or trout egg with elevated germinal vesicle, the
smelt egg has this area almost level with'the rest of the
yolk surface (see diagram'Of egg)*
fertilization, however,
brings about the raising of this area into a polar, lenticular
The shell is transparent and under the high power of a
compound microscope with transmitted light shows numerous
minute pores.
Thompson ant fan Sieve (1936)-saw- similar
pores in the egg shell of halibut gave'It a "'honey­
combed appearance”,
In the smelt *s closer relative - the
trout, the egg shell is porous as well and according to Wolf
(1936), no doubt, allows the slow diffusion of. water into ■
the egg.
But Andre (1875) thought the egg shell was non-
porous except at the rnicropyle; this idea was, however, found
incorrect later.
Above the germinal vesicle will be seen the
funnel-shaped rnicropyle.
Around the :rnicropyle .(Fig. 14) Is
attached a cap-like accessory structure (zona, radiata externa,
Shreabausa, 1994) of the same material as the shell, fitting
snugly and superimposed upon the latter.
This eap-lik®
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affair0 upon extrusion of the egg into the water* everts itself and assumes a funnel shape* thus apparently aiding the
rnicropyle in receiving and..guiding a spermatozoon into'the
when the egg settles to the bottom this.zona radlata
externa attaches the ovum to the substratum. .The rnicropyle
finally closes by contraction.
■fater Absorption
It is now well...known to fish culburists and fisheries
biologists that egg# lamedlately after the union of-the pro*
nuclei of the■two■germ cells undergo a process known as "water
this process Is merely the absorption of water ■
into- the perivitelline space so that in due time the ovum be*
smss turgid and the shell .stretched fully in contrast to
the partially collapsed state of oviposition.
This measurable
affect on the ova is said to be brought about by a more or
leas viscous colloidal substance extruded into the perivi­
telline space, from, the yolk by slight shrinkage of the yolk
mass which occurs when.the egg is laid.
This chemical sub­
stance possesses the power to dilute, itself through osmosis
(Bogucki, 1930} to a certain concentration, until equilibrium
between the substance and the surrounding.: medium becomes
established so that further'dilution cease® to take place.
Both rip© unfertilized and fertilized ova ..were measured
across the longest diameter by a micrometer eyepiece.
was done to determine how much water absorption accompanied
The ripe ovarian ova vary in diameter t m m
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0*867 mi . to l.GBO mm.
with an
averag© of 0,930 aim.
tabulation of the measurements is -compiled (unfertilized)t
fable 711.
Diameters of Unfertilized Ova
Blameter la am.
.O',850 '•
• '
0*969 •
1.008 ■
Average. ‘
These eggs were taken fro® a batch of eggs that was spawned,
subsequently, fertilized', and incubated.
The period involved in the process of water absorption
In the Pacific salmon, for instance, the period any
extend up to 48 hours, but within the first hour or two,
absorption is rapid and almost completed; thereafter absorp­
tion goes on in a very slow rate until full completion of the
On the basis of the data at .hand similar conditions
exist in smelt* though indications are that absorption is
completed within the first two hours after fertilization.
Comparing the diameter of the egg shell measured two hours
after fertilization and of the same prior to hatching, so
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appreciable increase in diameter fe&s been noted,
This leads
us to suppose that *water hardening* sight have been fully
completed during the first two hours, Is not im­
possible that it may .have been completed in. the first hour or
even earlier,
Again it may be possible that this process con­
tinues for sometime after, as has been shown by Sutter (1908)
in the case of the qulnnat salmon.
If it does, the ©mount is
negligible so as not to ©oiaaand any special interest other
than for exact quantitative determination.
To ascertain how much increase in diameter would result
from absorption of water, measurements were mad© on .a number
of water-hardened eggs from the same batch that- had been used
for measurements of the unfertilized eggs.
Table fill,
Diameters of Water-Hardened Ova
Diameter In mm.
13 .
i( f
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The average diameter of tie ova 1.X00 am* with
commonest-size at diameter of 1.105 mm.
nith Table ¥11 it is readily seen that there is am increase
in the diameters .of the eggs'caused,.no-doubt* by'water ab­
This is equal to the difference between the final
and-initial diameters or 0.171 of a millimeter,
in percentage, the' final diameter after water absorption was
fully completed, is greater than the initial by IQ.4 per cent.
This percentage increment is quite high for the size of the
eggs but in trout, as high as 2Q per cent is reported (Wolf,
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It tea been mentioned la a previous section that a
minute rnicropyle perforates the egg shell above the germinal
Insemination of the egg is only possible through
this crater-like orifice*
When fertilization'is completed,
the rnicropyle close® and developmental activity within the
ovum commences immediately.
Fertilization produces a number of effects upon the
egg and the reaction of the egg to the entrance of the sper­
matozoon Is quite typical of that of many other teleoats.
An immediate and readily observable effect of such fertiliza­
tion is "water hardening" by osmosis,
merrhaa called' it "water swelling".
lydor {1804} on Qadua
This process distends
the egg shell and renders the egg turgid owing to the entrance
of water.
However, according to Ryder impregnation of the
cod egg is not.absolutely necessary, before water, imbibition
could take place for the unfertilized egg absorbed water just
as if fecundated, but a much longer time was needed.
Simultaneous with the above process is another.
This is
the migration, or rather the aggregation, of the protoplasmic
material at the germinal area.
Ryder (1884) found a large
amount of protoplasmic substance present in the egg of cod
and observed its movement or streaming to one pole to form
an elevated blaatodlso.
A large amount of protoplasm appears
to be a general characteristic of many teleostean eggs for in
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many of them an elevated blastodisc is formed after fertiliz­
In the smelt egg active protoplasmic migration could
not he observed because of partial opagueness of the ovum.
Bat the reaction of the egg to insemination' is the seme, the
formation of a highly elevated blastodisc which Is lenticular
In shape.
{For"a detailed discussion of protoplasmic stream­
ing nee Ryder, 1884.)
The lenticular mas# of protoplasm is
■decidedly brownish, contrasting sharply with the rest of the
whitish yolk which is translueently opaque.
The migration
continues over an hour-after insemination as shown by the
progressive increase in the size of the disc .
■during the period
Soon after.the formation of the blastodlse, first cleav­
age starts and is completed about the end of the second hour.
Thereafter subsequent cleavages follow,in'a fairly„slow or
rapid succession depending upon the temperature.
This was
shown by some'eggs having four cells 5 hours after fertiliza­
tion at lower temperature and 8 t© lb pells in in­
terval at higher temperature.
In other fishes the start of
first cleavage ranges from the first SO minutes to,the first
two hours. 'Thus Hildebrand and Gable (1938) reported first
cleavage in blanny (Hvpleuroehllus gemiaatus) to have taken
place from the first 1 3/4 to 3 hours; Kuntz {1916) on
Cyprlonodon varlegatua, 1 1/3 hours end ©a Ctenogobius stig­
ma tus.
30 minutes; Wilson 11899) on Serranas atrarlue. 3 hours
In smelt, cleavage is typically teleostean and the first
sign is the appearance of a faint meridian groove across the
top of the blastodisc.
The groove gradually deepens end cut*
through the mess of the protoplasm towards the yolk.
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At the
completion of the process two blastoraeres with alight con­
striction at the bases art produced {fig. 15)* ■ Within an
hour or so afterwards,■the second cleavage follows {lapses
between stages variable).
As in the first, the second seg­
mentation furrow runs meridionally and at right angle to the
This divides the protoplasmic mass into a quartet of
At this stag© the cells are still compar­
atively large {fig# 16).
"Unlike other animals such m
echinoderms.'Amphloxus, or
amphibians, fish eggs do not exhibit a double quartet forma­
tion simply because the double third cleavage furrow is,
likewise, meridional instead of latitudinal or equatorial as
in these animals#
Hence we find no upper ant lower quartets#'
Although' the completion, of the third cleavage la many teleosts
results in the production of 3 cells, the blastomeres are
arranged in two linear rows of 4 ©ells#
Consequently, the
fish egg at this time loses the radial symmetry of the blast­
omeres so beautifully shown in holoblasti© eggs#
The 8 ©ells
in the smelt egg occupy one plane ss in other teleosts.
is brought about by double meridional cleavage planes that
cut parallel to and on either side of the' first plane but at
right angles to the second {Fig. If).
The ©ells are quite
small and those in the middle are slightly compressed so that
the polar view shows them to be rectangular'or nearly so is
The next ©vent is a repetition of the process observed
in the third cleavage.
It is also accomplished by double
meridional cutting, with the exception that the locations of
the axes this time are on either side of and parallel to the
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egg e&a&l
* gentlMl reslel©
» oil g X o M «
j> » s *
* yolk staaa
« zooa rat!lata
m le r e p jle
p a r l v i t a A l i w i a p ie e
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
figure 14. Semi-dlagremat ie draw­
ing of tii© unfertilized egg of the
smelt showing the rnicropyle end
its relation to- the germinal reel*
ele. Sona radiate externa is
shown in place prior to aversion.
61 tines natural sins.
Figure 16* Camera lueida
tracing of the S-eall stag*
61 times natural size.
Figure 16. Camera luelde trac­
ing of the 4*eell stage* ! 61
times natural size*
Figure IF. genera, lueida
tracing of the 6*eell stage.
61 times natural size.
Figure 1©* Camera lueida trac­
ing of the 16-cell stage. 61
times .natural size*
Figure 19. Oeaera lueida
tracing of very late seg­
mentation (16 hours). 61
'times natural size.
■ ■.■■■ : ■
, •
■V ■
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
second cleavage plane and perpendicular to the.first cleavage
Completion of tills segmentation brings tie number,of
cells to a total of 16.{Fig* 18).
The blastomeres are still
readily recognisable■and can be counted with ease*
At this
stage a very marked change in the arrangement of the ©ells
takes place and results la the restoration of the original
redial symmetry,of the blastodermal 'cap. .
At the fifth cleavage, the segmentation furrows digress
from the usual at-right-angle-ho-each-otber relationship,
which is evident in.the first four cleavage stagesj the
grooves follow no definite direction is cutting the ©ells. ■
The difficulty in tracing the
©ells becomes greaterand no
serious attempt was made to follow the appearance and direc­
tion of the furrows.
'The blastoderm, however, is no longer
one-cell thick on account of the fact that some cells at the
top of the blastoderm, divide faster than others*
As sub­
sequent segmentations proceed the many cells produced become ■
correspondingly smaller and smaller so that in. whole speci- ■
mens of later-stag© {16 hr. - Fig. 19) one can'scarcely see
the boundaries between ceils.'
At this time, the
appears like a single mass of protoplasm*
fils on {1889) in. Serranus atrarlus. Solberg {If35®) la
FuMalus heteroelltua and Budd (1940) In Parophrvs vetulus
found the beginning, of a segmentation cavity as early as the
8 cell stage.
This Is found la smelt also*
It should, b#
noted, however, that the segmentation cavity in the earlier
stages of cleavage is not readily recognizable as such*/ Often
It shows itself' as- small spaces underneath blastomeres because
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there is yet no definite arching of the ceils'to fora a doma-'
shaped cavity as we see in amphibians,'for example#’ The arehing of the cells occurs much later.
Consequently* there is
no clear-cut biastoeoele*
At about 6 hours, the segmentation cavity is fairly en­
larged and discernible#
This cavity is foiaed by freeing, the
yolk of adhering cells at the region o f -the central periblast
(yolk nuclei, chose existence was first discovered by here-'
boullet, {1854) but chose origin was first traced by Agassiz
and Whitman {1884.) on gteBQlabms to be derived "from the
marginal cells of the blastoeisc'V) and the cells finally heap
on top of the blastoderm.
At a later stage (fig* SB) the
top layer of the blastoderm becomes thicker than Its edges
and is several cells thick.
The truly typical eccentric
segmentation cavity, attained only at a very,late cleavage
stage, Is elongated and convex conforming to the convex yolk
surface over which It has developed.
The biastula stsgd
lasts until about the 18th hour when other modifications in
the embryo occur preparatory to the next process, gastrulation.
Meanwhile pronounced changes' in the blastoderm are
taking place.
The cells progressively diminish in size as
they divide,, the blastodermal dome becomes more convex by a
pinching process around the edges.
Vhile the above event® are taking place, the cells, are
simultaneously spreading over,the yolk.
The blastodermal
periphery Is beginning to thicken; eventually it gives rise
t o 'the germ ring, whose origin in the thickening ©f the'" margin­
al edges around the blastoderm*
The thickening in turn la
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brought about, according to the observations of Gotte (1873) .
by the combined processes of thinning of the central portion
of the blastodisc and the, invagination of'the peripheral cells.
Is some aselt eggs the gei® ring is fully formed at 1® hours;
Is others even later*.
Fig.. tE-'Cl® -hr. glycerin# Mount} show®
the blastoderm with a thicken®# edge, the-''few ring.
of the eggs belonging to the seme stag® show that gastrulation
Is Just starting .(Fig* 21}., The process.
.is accomplished by
centripetal involution of a layer of cells.(primitive ©Moderm)
from' the germ ring near the dorsal lip of the blastopore into
the blastoooele.
Growth continues and the germ ring heaps
rolling over the surface of the yolk towards the equatorial
region of'the ovum.' .At this stage ~the ■dorsal lip of the blastopore Is being-formed by involution.
The germ, ring■
against the yolk mass quit©-, tightly so that a ..groom. around
it is formed, with the uncovered portion of the yolk mass ■
bulging out prominently*'
This is the yolk plug- (Fig,-Ml ■,
which occludes the blastopore*
as epiboly proceed#., .-and the
embryo become# distinctly marked.on the embryonic shield, the
blastopore continues to move -.toward® the vegetative pole,
relatively much, quicker at the "cephalic end (ventral lip
region) of the -embryo-and at a slower rate at the .region of
the dorsal lip of the'blastopore#
The'result. Is that the
blastopore move# away fro® the anterior"" region and lies closer
to. the tail tip#
There it finally coalesces and encloses the
la sea bass Wilson .(1889) described epiboly a# most
rapid about the ventral lip of the blastopore>ni diminishing
in rate posteriorly, eo that the ventral lip of the blastopore
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
lip ©f blastopore
io r e a l
s@p»Btati©m cavity
y o lk ggftfiijtja
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
figure 10. A photomicrograph of a sag*
ittal section of a segmented smelt egg,
fitefl 5 hours after fertilization, shorn*
lag the beginning of the blast©®®®le.
136 tinea natural size.-.
Flgur® II*. A photomicrograph of a sag­
ittal section of an 18-hour embryo show­
ing the beginning of gastrulation and
the thicteaing of the edges of the
blastodiae preparatory to the formation
of the germ ring. 136 tinea natural size.
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finally coses to lie on the ventral side of .the embryo near
the dorsal lip.
Embryonic Development
When the blastopore finally fuses gastrulation is compitted,
The.embryo is dlploblastic and possesses.a primitive
gut, the archenteron,
Later processes are primarily concerned
with mesoderm formation which may, or may not, synchronize with
the differentiation of the ectoderm and endodOra.
coincides or comes soon after the start of mesodermal develop­
a detailed discussion of the processes above men­
tioned, lyder*s dissertation on cod
and Wilson*s on sea bass
may be consulted.
At 25
hours (Fig. 2 ) In smelt the g e m ring is at the
equator ofthe ovum.
At the same' edge ,of the
{above the dorsal lip is thicker than the rest of the per­
This is the "concrescence" that forms the embryonic
Growth has projected the embryo along.the long axis
of the shield,
At this point, however, it should be remember­
ed that the embryo does not develop at the expense of the •
lateral lips of the blastopore by the coming together of its
right and left sides,. In Serranos atrarlus Wilson {1889| had
shown that concrescence utilized only a very small part of the
lateral lips, the embryo being chiefly derived from the blasto­
derm anterior to the point where the blastopore fused or'dosed.
Furthermore in .fundmlus heteroolltus the "keel* ..{future embryo)
is derived from the thickening of -cells that lie along the
center of the long axis of the shield.
In smelt at the commen-
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■» *atory9
em.8 ' *
e;;;bryonlc stoleId
«* germ jtiag
* gupffer*« vif&aU
• yolk plug
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Figure ££• G m m m lueida treeing of an 18-boar
embryo showing the e o m m n m o m n t of the germ ring*
61 times natural site*
figure IS. Camera fsieMit tree lag of IS-teur embryo showing tbs
g e m ring at the.equatorial plate, alee, the embryonic shield '
■with the embryo projected m It# §1 times natural also#
Figur© 24. ■Camera lueida traeing of a Si- f e w embryo projected
aloag the long aria of the embryonic shield. @1 times natural
R eproduced with permission of the copyright owner. Further reproduction prohibited without permission.
cement of development of the embryonic shield only a small
protruberanee on the surface of the blastoderm is ■apparent.
However, as the shield advances over the surface of the
blastoderm this protruberanee merges with the general, sur­
face so that at 28 hours, when the blastopore"!® approaching
closure, the embryo as viewed ( In 10 per cent glycerin®
solution in 80.per cent alcohol) under a reflected■light la
still hardly discernible from the rest of the shield save a®
a white opague band across the embryonic shield,
At St hour*,
the embryo Is unmlstakeable and is well marked off though not
yet highly ridged; its ..anterior end 1® aor# expanded because
of the beginning of the optic cups,
It this stag® the blast­
opore is already coalesced, even leaving no traces of the
line of fusion.
In fact, in some eases- and as early as 31
hours, -the yolk sac '(portion of the embryonic shield that
did not give rise to.the embryo) fully shuts .off the yolk
mass and the embryo Is half-way across the convex surface
of the -ovum. /Both end® ©f the embryo- are delimited from the
rest ©f its body by slight elevation®*'
From this time on
the embryo develops rapidly* - At the csudal end new somites
-are continually.being added*
Changes in the cephali® region
are taking place step by step; organs -are making their first
This period Is termed the period.of embryonic
development* At 39 hours (Fig* £4), the Kapffer*s vesicle (post-anal
gut of Summer, (1900) is already apparent*
It is held to
account for some aspects in the growth of the embryo.
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As re»
gards It® origin opinions differ.
Kupffar himself (1868)
regarded it a® an andoderaie invagination from the dorsal
surface; other® (Cunningham, (1885) and Agesein and Whitman,
(1884) believed it to be a vesicle between the en&oderm and
tha periblast.. On the other hand, Schwarz (1889) stated that
at the ie a cavity among the cells of the caudal
Wilson (1869) believed otherwise and said that in
Serranos atrarlua it was produced by a process of infolding,
while in salmon©ids it Is produced by •hallowing out of a
solid thickening*.
freeing of its origin in smelt was net
At 50 hour® (Fig* 85),' the embryo has grown in bullc and
i® well elevated fro® the surface ©f the yolk.
The tall end
slopes gently towards the vitellus and Kupffer*s vesiele is
still prominent.
The cephalic region is thicker than the rest
of the soaaj the head now present® two slight.'curvatures,
following the contour-of the brain underneath; the optic cap­
sules bulge out laterally and tie- top view of the head appears
anchor-shaped! ventrally the cephalic front simulates the fees
of an owl.
It is noted, that as yolk material is being util­
ised by the growing embryo, the ©11 globules are becoming
fewer in number but definitely larger in size than they were
at the time of fertilization.
It s m m m that as the oil, in­
terspersed among the yolk particle-®, is freed owing to con­
tinuous utilization of yolk, the oil droplets tend to combine
together into fewer but larger globules.
Simultaneously other organs are developing rapidly.
At 67 hour® (Fig# 86), the cephalic flexure is already In-
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» #'f@
* tss&ttvr** ▼««!©!»
fe e a rt
* ©tie vealel*
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Figure 25. Camera lueida tree lug of a 5Q«hour
embryo showing Kupffer*s resleie* 61 time®,
natural aim#*
Figure 26. G m m u lueli® tracing ©f a if*
hour embryo. iufffat*® Tea'lele Is gone. ■
61 times natural sim *
Figure 27. .Camera lueida treeing of a 72-hour embryo
with the tall freed from the yolk. 6 1 .times natural sis®.
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dieated, but- the embryo has not yet completely encircled the
as It develops the head' -expend* further because of
the formation of the lobes of the brain; at 72 hours, the
flexure la more'.pronounced and the ventricles of the brain
are very apparent# ''At this stag©. £upff®r-*s- vesicle is so
.longer present; the auditory vesicle thus far has developedinto a kidney-shaped organ end the heart,, -though yet' non­
functional, lies on the surface-Of .the'yolk below'the nape*
At. about this time the optic cup enoloeear;the,'lease-of the. ■
eye completely {96 hours}*-- The heart occasionally pulsates
faintly at first-but from-113 to 137'hours, it. starts-fuse-'.'
tioniag normally.
The .blood .could be seen coming in and-.-
going out of the heart.
By this time, too, the embryo has
formed 1 1/3 to 1 1/2 loops around the-yolk.
At'about the
time the occasional pulsation of the heart is observed, the
' -eyeball (choroid coat) is beginning to show pigmentation
starting from the dorsal ria downward and later spreading
all over -until the entire ball appears black#
The optic vesicles, the-earliest senhe organs to make
an appearance, are perceivable as early as 39 hours as later­
al ©vagina t ions from ..the brain in the form of'-a blunt spear­
head but with rounded barbs.
The lenses., unique in that they
are made up of concentric layers, soon follow at 67 hours,
and'by 96 hours, the-optic- c'up- has completed fusion at theventral side of the leas* ‘ At about 72 hours, the tail be­
comes free of the vitellus {Fig, 27}.
At 80 hours the embryo
has completely encircled the yolk sphere once.
Growth con­
tinues to be rapid until the time-'the heart begins pumping
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normally and then slows during:the' differentiation of organ
At 74 hours^ of incubation occasional movements-
of the embryo may be observed.
Soon after the tail has been freed from the yolk back­
ward 'growth of the■intestine as a blind sac becomes evident*
As the some lengthens"by addition of new' somites, the di~
gestive tract also lengthens.
At 97 hours', '■the,, tract Is
approaching the proctodaeal pit, which is located some dis­
tance anterior to the caudal tip of the notochord* '■By the time
the anus is fully .established (fig. £9, by resorption of the
■ line ©f fusion between-the proc.tedaeiu£>nd ,rectus) somatic
jselanophores, which appeared at- from 111 'to 120 hours, are
well developed, showing radiating root-like processes*' These
s;;aelanophore© appear,.likewise, on the surface of the yolk
■sac -mostly on the ventral side*
Two days or so earlier than
the establishment of the anus, the stumps of the pectoral fine
appear (fig. 28) on the lateral sides of the body Just behind
the auditory vesicles.
The stump la a mere fis.p'.of skin ;®jsd
Is;roughly triangular in shape with the broader base attached.
As development proceeds, the stump constricts' .around the base
■'...'while the fin expands into, a fan shape.-; At the time of■hatch­
ing, the fin is much broader than its 'base.' .The pelvic.'fine
nr© absent, but make their appearance much- .'later, in post-' ■
.larval life..,: .
By the time the heart starts functioning normally (be­
tween. 113 to 137 hours)., all organs systems are well outlined.
As noted above a sort■of lull in development ensues'and all
further progress is primarily concerned-with the differ-
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• sun#
* intestine
' m
p+ f* » f#et©3»l fin
- proctodeum
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Figure 48« Camera luelda tracing ©f a 97-hour
embryo showing the intestine approaoblng tJie proetodaeum.
■figure It* Camera lucida tracing of a 147-hour
embryo showing developed Intestine and tbe ©har&oterlstie
pigmentation on the ventral side from the yolk sac to
the tall region; also on yolk mass* 61 times cultural sins*
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©©titties and specialization of the organs.
Nonetheless the
aaabry© continues aiding somites posteriorly with the result'
that at hatching the embryo has looped 2 1/E to
■around the yolk.
At 159 hours, the embryo begin® to wiggle
constantly and distorts the loop by assuming all kinds of
positions with regard to the axis of attachment.
At this
time, too, the eyes are already darkly pl@aented; the semi­
circular canals are distinct; the yolk mass is somewhat
laterally elongated and grooved at the middle portion which
the embryo fits.-snugly.
Another notable change is the
physical appearance ©i the embryo, which at this time is be­
coming increasingly transparent.
Some time later the eyes,
with lenses bulging out prominently exhibit a" yellowish©rung© sheen by reflected light.
At this time too, the
embryo has become coapietely transparent; it is practically
invisible except for the pigmented eyes..
At. this stage, the
embryonic development is completed and the embryo will soon
This stage is reached in 9 to 10 day*-of incubation
|I1# to 240 hours1.
Loosanoff (19501 reported that the in­
cubation period from fertilization to the hatching time re­
quired about 11 days.
In our observations a few individuals
even hatched late in the 8th day; the majority hatched on the
9th and 10th days and we ©all this the hatching period (when
half or more of the batch of eggs have hatched).
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QiRtl* -f TY
Jh W A b H I N f i '
j£tate4&B*4»-< £-
.. KL .
£ LMfcjMtirfint y/WMfff* i r 1 1 idrtiMi In 'i^hl
-*** ■» a* «■< *-l|.
* -j , ■ i .4*1 it^SUl
wifiytjr1*1*$w*sw w r^tlr
* filjttmqr jaf| 'l>
irtif «sd
p$todrtoda talh&wfi
U N fV e rtS IT Y
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
f lO O K
PAlf fll. •MlGfi&IJSM OF BATCHI»a
, '
.Means of Hatching
Our i»f©'rai&ti©;
a''regarding hatching' is still very meager.
According to Needham (1931) lerr was probably the first in­
vestigator who suspected that certain enzymes secreted by
the embryo were responsible for the hatching and liberation
•of the young from its shell.
McCay (1936) presented a brief
discussion on egg hatching and showed that, u p 'to that time,
hatching was still a controversial subject.
In fact up to
the present time, no material fact of significance has been
discovered to throw more light on the subject.
However, two
definite viewpoints on hatching have crystallized and in
seme other animals a third (osmotic hatching)-,--and possibly
a fourth type have been reported.
One hypothesis maintains that hatching-,Is. a mechanical '
process of some -sort* -It is rightly claimed -that at hatching
time the embryo within the shell keeps wiggling constantly
with strong-lashing of the tail against the,-shell (Armstrong,
1956 on ffuadulus).
In birds hatching is Initiated when the
young chick pecks m hole through the shell:' (McCoy, 1936) but
the- absence of a .beak in fishes -precludes, all -such, possibility.
Even in the case of grunion, where'the eggs are deposited la
pods and hence .susceptible to more effective enzyme aetion,
their hatching may be in part mechanical. 'This could be ex­
pected because the waves shift the gravel on the beach in
which the -eggs are deposited, and therefore abrasion helps
the fry break through their shells.
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j '
A -second''hypothesis maintains-the thesis.that batcMag
%j/\ Is solely chemical. In'nature through the enzyme digestion'of
the'ohorion or egg shell*
I f ■a mechanical process- is involved
it i©-‘
-merely to supplement the enzyme*
In 1912, Wintrebert
experimented on trout' embryos ready to- hatch; he paralyzed
the® with'a weak solution-of chloreton© { 5 parts, to 10,000)*
■The result obtained was the retardation of hatching saveral'.
hours and he noted, likewise,•that the perivitelline fluid,
turned sirupy at the oCHOpletlon of the'incubation.'period.
-ascribed this- sirupy consistency to the digestion of the egg
From this observation his conclusion was that mechan­
ical movement of the embryo was in no m y responsible for th#
opening of the shell.
Nevertheless, he admitted it played
an important role after the first hole -in the shell had been
Heaotti (192?) dissented .from:this interpreta­
tion of Wintrebert, and although recognizing the presence
of'proteolytic enzymes., still insisted .that'hatching in
osseous fishes 1s-:a function of pressure from within as a
consequence of swelling produced In the egg .contents*
later finding® on some other fishes tend, to .favor the view
taken by Wintrebert rather than that of Heaotti because thus
far osmotic hatching (which the latter proposed.) is known
only in invertebrates such as in Daphnla and other cladoeeran®,' copepod® and ays ids.
That enzyme digestion of the shell .!©■"a- definite' factor
in hatching is now well known.
In salmon it has been'observed
now and again that hastened by overcorwdlag■Is
The view'taken is that the 'enzyme does not only
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help the Individual embryos to hatch out by themselves hut
that once liberated Into the water, it helps to dissolve
shells of other embryos from without fwtntrebert)*
la other
worts, the enzyme earn work from withla eat from without,
zyae action has also been established la other fishes*
la' (1926) preseat is f m t t a farlo. Gaaterosteus .
aeuleatus. Gob jus panamalias. ate.
Armstrong (1936) found an
enzyme notion In fttadiitus heteroollltus.
But where end how
the enzyme is secreted Is again a matter of controversy*.
(1946) maintains it is,a secretion from the body surface of
the larva, while Berglot and Wintrebert (1926) said It ie t r m
the frontal lobe of the brain*
Armstrong is a product
of some glands in the mouth (fumdulus) whereas 'la trout Boardin (1926) to be free some, sort ©f ephemeral glands
that appear in the skin of the embryo when ready for hatching
l«rt which later diaeppMr,
K U 422£ S U S S Jatchia*.
this according to MeCay "is quite a wonderful mechanism if it
Is true"*
Boardin*s is, however, a further confirmation of
earlier findings (Wimtrebert, IfIB) that the secretions were
produced fro® temporary uni-cellular epidermal glands*
strong reported a parallel case in Funiulaa*
.Be claims that
unicellular glands located In both the. mouth and pharyngeal
cavity disappeared after batching was. accomplished.
Experiments conducted by .Hayes (1930) gave indications
that the enzymes could be equally'hamful t® the embryo.
salmon he proved its'lethal effect, upon the embryo such that
according to Seedham (1931), "there is literally a race as to
whether hatching or death will take place first"•
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Adaptation to Environment During Incubation
. As has been discussed in the section of spawning■habits,
smelt eggs are left lying above, the water line after a favorable tide, has ebbed 2. hoars or so*
Haturally incubation is
primarily on "dry land**,' because the ova are, under water onl^
. few hours each-day. (tire high tide® daily).
From this cir­
cumstance, it is readily seen that in order to bring'tha
"..successful completion..of incubation and subsequent hatching,
the time of oviposition''so chosen .as:to synchronise
. perfectly well with the next series of -high tides| so that at
'the tine the ova ©re ready for hatching there would be water
above the®.
At this, point a question may be askeds 'In ease
. of an occidental timing (which is possible-..but not probable)
such that hatching period is reached when the■tide i® far
down the beach, will the embryos still hatch despite the
absence.of water above-theaf
k second question follow®, what
-'provisions ©re taken, if any, by the smelt to obviate danger
arising from such, a contigeneyi
To answer these questions la
the light of observations made, will lead Vs. to the realisa­
tion that smelt have so adapted themselves/to.their environ.■ meat that no danger at ©11 face® embryos even.-if such oce&aion
as mentioned above may arise.
It can be said safely,, without
fear of contradiction, that the smelt have so adapted them­
selves to hydrographical conditions along the beach that their
timing with the tidal series le perfect,
furthermore, in
analyzing‘our observations; three safety factors become obvious,
each of which contribute greatly to the preservation of the
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fh©s© are: ' 1} the selection of the level on the
'■ spawning beach where the ova are to be deposited is such that
at no tia# 'during any oae twenty-four hour period is it not.
reeehed by either the morning or afternoon high tide or both,
this explains why the smelt would never spawn at uppermost
limits reached by a series of high tides but would wait until
the tide has receded 2 or 5 feet down the beach*
That they
wait for the'.,tidal.drop is very well known but. how they seas#
■the' right moment is altogether unknown.•'In Maple Grove, the
-•. .
:';ehsiee corresponds approximately to a 7 feet-level above mean
■ 'law.-water. 'Thus"such a selection provide© that the 'develop*lag eggs should ''be- under water at least once daily or in many
.. eases twice, under both aorning and afternoon high'tides.
Develcoirg ova can. withstand a certain amount, of deal*
cention without suffering m
adverse effect. - lot infrequent­
ly eggs are left on the beach exposed to the elements.
is specially'true when .spawning takes place on cairn days when
wave action (responsible for burying ova under gravel) is
either slight or absent.
On such occasions the writer, found
. collapsed eggs,that were from all appearances desiccated and
But examination of such eggs showed seme embryos with­
in were still alive and that the original turgidifcy of the ova
could b© restored upon immersion in sea water*.-
This is cer­
tainly a beautiful adaptation that must prevent destruction
of many embryos stranded on the beach.
Thompson (1919)
grunion, and Loosanoff (193#) on smelt, reported the same.
In case of necessity the smelt may delay hatching a day t/
or even more.
Loosanoff claimed that embryo®,' kept in moist
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sand until the 16th day' of incubation, would not hatch; they
»@r® normal, but dormant.
But on the preceding days beginning
thr 11th and thereafter until the 16th day,'., embryos would
hatch whenever placet;is water.
He concluded from this that
embryos will not hatch unless they are under water^
We ob­
served the same phenomenon although ours extended only through
the second day*' This is certainly an important device especial­
ly beneficial to embryos that have been washed,ashore af^putats
beyond the reach of an average high tide as .well as to those
ova accidentally laid on upper levels by the mother smelt*
This ©an only mean one thing ana that is it bestows an added
lease on life upon the embryos so that they say hatch on
succeeding high tides*' like Loosanoff we made.the observa­
tion in the laboratory,
fro® a batch, of eggs ready for hatch­
ing several embryos were kept in a petri dish with moist sand
ant the dish.covered to prevent evaporation of the moisture
necessary for the respiration of the' young*..
For over S@ hours
through the second day no hatches were'recorded*
Tet the
controls that were covered with water and,slightly agitated
hatched -at once.*
The experimental lot showed -the embryos
were •normal in every way; they wiggled, .occasionally and' tb®
heart could be seen beating*
At the end of the second day
all eggs in the lot were put bach in water and. very soon tbs
fry escaped from their shells.
Digging also.on'the beach
where the eggs were being: incubated disclosed' no evidence of
hatching in the absence of water over them despite the fact
that numerous embryos were found ready for hatching since
when they were agitated in water they promptly hatched.
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they may forego hatching whenever necessity arises 'in allimportant to the welfare*of the species. ■Thus embryos would
not hatch on "dry land” but'would wait until the aeact high
tide comes to the rescue.
fetching in Smelt
I© definite information on smelt as regards the true
factors involved in the process of hatching is available.
Neither did we. take any step to ascertain them.
It is deemed
wiser and ator© safe to take a middle ground-by...adopting'the
hypothesis that.hatching here is a function involving both
mechanical factors as wall as enaymatio ..operation.
disproves one way or the other this interpretation would be
adhered to.
'Observed.on the day ©f hatching, there was seen an active
movement on the part of the embryo within': the,shell. ■The Im­
prisoned fish kept rolling within the shell .-and the tail kept
beating intermittently* while the bead pressed, against the
shell in such a'way as to stretch it.
Skile it is not entire­
ly out of the question to surmise that some kind of m u e j m
operation nay weaken the shell from within,' there 1 ® 'no deny­
ing the fact that mechanical processes, such as violent move­
ment of the embryo together with the agitation of the gravel
on which the ova are.attached, play an important role in the
liberation of the young into the water.
In its natural en­
vironment agitation (due to breaking waves against the beach)
is almost invariably present, so that it would, not he sur­
prising if hatching becomes largely the function of the
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The fry batched out with'the bead foremost* °
If enzymatic digestion of the shell, as has been estab­
lished -in some other fishes, does exist in ...smelt its actios
'.must logically be coif i&ed withinindividual eggs and it
cannot in any way influence the hatching of other eggs be**
cause of the very small amount of enzyme that can be produced
from each egg and the infinite dilution it will suffer upoa
"discharge into the water*
Furthermore,, external enzymatic
influence can'only .'effectively exist if and when egg© are
deposited together in a nest such m
in saloon (Oncorhynchus).
trout (Salao), large-mouth bass fAolitee salmoi&ea)* catfish
(Amelurus) or conglomerated'such as in ling cod (Qohiodoa
elongatus). yellow-perch-'{Perce flaveseens}, herring; (Clupea)
©r' incubated in the south ©f the sal© such' as in tropical
catfish ■(Arias I.
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m t
uam i , postlahvab, asp
Materials on Band
The post larvae on hand eons 1st of few samples of' 4-tay,
5-day, 10-day and 15-day larva#*
The complete lack of
approprtat© facilities la the field to carry oa artificial,
rearing operations, together with the extremely delicate con­
stitution of the larvae, contributed much to the failure to
produce later oostlarval stages.
Later stages were supplied,
fro® the collection la the Duwanlsh and .Puyallup rivers.
The writer was unable to rear larva# beyond the age of
IS days" after hatching at which time they beer a© resemblance
to adult fish.
At this stage the larva© were 7.15 mm. long
©a the average, and were essentially such like,the larvae at
the completion of the yolk absorption stage except that the
former differed from, the .latter la the site of the lateral
chroma top bores which by. mow had become larger, in site..
It is Indeed regrettable that length stages between
.lengths of 7.15 m * ■and if m u are not available.
This leaves
a gap in our knowledge of the life history of the smelt.
the light of specimens on hand such stages.would and should
show the details of development of myotome#, the differentia­
tion of the digestive tract, disposition of chromatophores
and the development of the pelvic fins because, the next avail­
able larvae (17 am.) show all the above structures la fairly
advanced development, although the pigments, fin folds, pelvic
fins still retain their larval character.
Samples of young
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fish between 18 mm. eat 3b ram. are unavailable.
Oa the other band, It in very fortunate t&at later postlarval stages {35 am* and upI ere available, representing
various sizes,.end- exhibiting the development and disposition
of melanophores until adult pigmentation is fully established,
the specimens were collected by. a small seine at the mouth of
rivers mentioned elsewhere.
" A "
stomach 'Soateate
hN,- ”
v| /''"
‘< V
Examination of the stomach of a If msu fish disclosed
a very interesting fact.
In the stomach ..were found dipterous
larvae in various degrees of digestion.
In addition a fresh­
ly engulfed mayfly nymph yet fully undigested was also found..
This is indeed, very Interesting because the. dipterous larvaeand the mayfly nymphs are fresh water organisms,
the feet
that the young smelt fed oa them suggests that the lancet
larvae are carried down the sea by river dischargee where
they are gathered by the small smelt.
This interpretation
seems unlikely because these organisms have certain anatomical
adaptation for keeping, themselves in fresh water.
The presence-
of fresh looking mayfly nymph In the stomach, with all append­
ages Intact and still unaffected by digestion* strongly in­
dicates that the young smelt go up rivers to feed, and
possibly they shuttle back end forth.
The. assumption was
proved correct because flagerling smelts are taken close at
the mouth, of rivers or caught in. sloughs as has been the ex­
perience of .loosanoff, Schaefer and Seymour (the last two related their experiences of catching the young smelt to the
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present writer) •
This habit of entering' brackish ©r freak
water is net surprising at all because some members of tbs
fatally t® which gymsaeau®
belong actually have
anadramou® M b i t s and the family is considered phylogenetically related to tbs true salm m
(Bigelow and Welsh* 1926),
which are truly analroawus la their life# ■
Sabit® of larvaeAt hatching tbs iky of smelt are perfectly transparent
except for the yellowish orange eyeball*
Soon after haring
been freed from tbs shell.* tbs 1arras swim actively la the
normal position, i*e* horizontally.
In the laboratory where
some were reared in Ohase Jars* tbs larvae have been observed
te react positively to lightf hence they .kept themselves on
the surface uniformly distributed if light is efually reeelvel
from all sides.or congregated at the side where light is
more intensely directed*
This positive response was taken
advantage.of when changing water in the jar*
A spot light
focused directly on the top layer or oa one side served te
attract the larvae to the source of light so. that a siphon
could be inserted to the bottom and the water siphoned off
without losing any of the .larvae*
Ivea in their natural
habitat indications favor such a reaction which only .has been
directly observed is captivity,
thin wee demonstrated by
plankton tows.on surface water during high tides when many of
the newly hatched larvae could be caught*
But nose of the
towe produced.any postlarvae (fry with fully absorbed yolk)*
This agreed well with the laboratory observations*
It was
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noted, for instance, that the larvae reversed their reaction
fro® one of positive to one of negative phototropiam after
the yolk has been completely ah sorted,
They avoided light
and kept themselves .at' the bottom of the Jar seeking places
with the least illumination.
From this set of observations
it Is inferred .that ■the postlarval'life,'during the first
feeding stages 1® spent deep down or close to the bottom
where light is less intense.
Other factor® sueh a® the
specific gravity of the yolk or the buoyancy ©wing to the
presence of oil globules and of a large air bubble at the
anterior end of the yolk mess may have kept the larvae in the
upper layers ■during the larval stages*
Whether these factors
played a role or not was not determined.
the .larvae
-It birth {fig*;#!} the young creature-is a slender
transparent fish with very prominent head made so by the 1
prominent brain and the sense organs .such as the eyes and the
auditory capsules.*
prominent leas.
is black*
fhe eyeball is pear-shaped with very
When preserved in alcohol the whole eyeball
fhe otic capsules are somewhat rounded spheroids
oa. .either side of the hind brain adjacent to the posterior
margin of the lateral expansions of the aldbraiau
The mouth
is slightly oblique and slightly subterminal in position.
It cannot be, discerned in lateral view.
From the dorsal side,
the mouth is invisible being hidden by the prominent flexure
of the fore-brala*
Immediately behind the ©tic sapsmles'ie
a pair of small fan-shaped pectoral fins, the only paired fins
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present at this stag#,
fhs body is slender and slightly compressed, with a prom­
inent yolk mass located at approximately one-fourth of the
body distance from the heat*
4 dorsal fit fold starting fro*
the nape rtrna posteriorly sat unites with the primitive lophooercal tail*
The tail fin in turn meets the discontinuous
ventral fin fold (interrupted by the vent) "that terminates
anteriorly at the posterior surface of the yolk sac).
lengths of the newly.hatched larva® rang® from 4 millimeters
to 6 millimeters, with an average of §*4 millimeters*
average is approximately five times the diameter of the eggs
at the completion of water absorption*
The bow-shaped metameric tayotomes proceed from behind
4h© pectoral fins almost to the tip of the caudal vertebrae*.
Pigmentation of the soma is very characteristic*
ophores are localized oa the ventral siie of the body and no.-,
where else, •The disposition of these aelanophoree is at ran­
dom oa the ventral wall of the yolk sac with some scattered
'oa the lower lateral; sides*'
A long "Chain of moderately- sep­
arate aelanophores (the vent -interrupt® the continuity of'
the chain thereby producing two segments) is distributed along
the ventral side of the digestive tract* . An anterior longer
chain originates from the median posterior wall of the yolk
sue and continues posteriorly to the tip of the vest*
.second, but much shorter chain starts some distance' behind the,"
.vent.sad goes down and beyond the caudal peduncle but not
quite reaching to...the.tip of the ur©style*
In many larva®
counts of the number of these melanophores are fairly easily
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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
made § in few oilers li is quite difficult if not impossible
due to fusion of two or more of these melanophore®.
second chain behind the anus Is generally .the harder te
count on aeeeuni of'partial fusion of certain of the pigment
spots at the hinder end*
However* in those that can be
counted easily* the number in both chains varies from In­
dividual to individual {see fig. 11}*
The anterior chain
has a minimus of 13 and a maximum of IS melanophore® but the
most frequent'numbers are 20 and El*
The posterior chain
ranges from f to IE saleaophoree but 8 and 9 arc very common.
Besides these two series of melanophores a few are fount,
on the dorsal and la tarsi sides of the vent*
two pairs of melanophore# Iconstant in number in all speeiments examined}, are found% one pair 1® located immediately
beneath the ventral base of the pectoral fins, and ©a either
alia ©f the heart* the second is slightly above the oesoph­
agus and some distance behind the pectorals*
melanophore# usually show radiating processes*
Both pairs of
This pig­
mentation patters is larval Hypomesus bear# a striding re­
semblance to the pigmentation in the Elbe smelt studied and
illustrated by fhresbaum {lit#}*
Hypurals are;laeking.
The yolk.mas# la ©void or nearly ao»
.Anterior to it '
and likewise, enclosed by the yolk sac i s e big air apaee*
The yelk material is completely,absorbed la from 4 to 6 day#
after hatching*
As early as the second day new .sets of melaa-
ophores make their appearance*
These bodies could be seen oa
either side of and slightly dorso-lateral to.the intestine but
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Just below the M f & t m m *
At five days (Fig# M ) , when the yelk bee.disappeared,
the original welanopbores have grown larger and new lateral
jBelanophores appear and extend from tbe pectoral fine to tfee
anus; they ere farther apart than -are tbe seashore of the
ventral chain®.
At tbl« time tbe dorsal an# ventral fin ray*
of tbe denial fin become faintly discerntble; no other fin
rays are visible; the larvae ramie from 6 to S*t am* with
•a average of .#•! mm*
Tbe part of tbe digestive tract
destine# to be tbe stomach la sore expanded than any other
Except for the slight tilting upward of the caudal
vertebrae and the slight prominence of the air bladder,
practically nothing ted taken place by the eighth day*
was, however, a slight increase is the length of tie young ■
fish over the average of the 4-day ®i«.larvae*
Growth appears
to be quite slow,, for elder larvae {13-day elij were ?*1S
on the average, or an increment of Just about 2 m u over the
newly-hatched larvae during a period of 13 days*
This, how­
ever, M y not. be taken as the normal rate of .growth of the.
young fish since they were under artificial com#Itlone*
nay be possible that tie growth rate Is faster when they ere
In their natural habitat*
It is rather surprising though
that other teleoetean fishes show a greater growth rets
despite captivity*,
-fins Kuntn (1913) reported a larval
length of l,h to 1.8 aw*'at hatching; 2*4 to 2*6 am* one day,
and 2*5 to 2.0 « u two days after hatching in thjt goby
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©bryanra. and 1.8 am. at hatching, 8.6 to 8.8' mm.
at 1® hours and 8*9 mm* In Anohovla mltoMlll.
and Cable (1930} found the larvae of orthooristls ©brysoptorua
{pigfisfc} to be'.© Em. la length Z 1/S days.after birth.
length at hatching was 1*5 wa.
la a flatfish (Parophrys
retainsI Budd {1060}. noted an increment la length of 1*8 mm.
in t days over am Initial length of 2.8 -mm. at hatching* or
am Increase of 4 wm* in 9 days.
The post larva at 17 ma. (Fig. ®g)r:;.flie head Is still
typically larval in forms the snout la blunt as before ami
rounded but the auxiliaries have attained some degree of
similarity with those of the adult.
Although the eyes still
bulge prominently laterally* they have become rounded .and:
have lost the initial pear-shaped fora in the pre-postlarval
The dorsal part of the head la beset with large
lieben-like chromatoporea, meat dense on .top of the cerebral
hemisphere| sparsely and smaller elsewhere. -Pigment spots
alee adorn, the.operoles.
;The myotowea ere sigma-shaped (^ ) end definitely resemble
those' of the-, adult, fish*
shin and muscles alike*
The body is -well' pigmented* both the
The .melanophorea are distributed ■
about the bases of the pectoral fine* cm either aide of the
abdomen* along.the lateral limes* on the-ventral side behind
the vent to the hypurals of the caudal fin*..-and all along the
dorsal side from the tip of the snout doms to the tail*
majority of selanophorea resemble lichens-, growing on reeks
or* baric of trees.
H I the' fins are definitely advanced in development,
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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
but still larval l a .appearance.
mile the pectorals show
tii® presence of few rays, except those dorsal t© the asym­
metrically upwardly tilted last caudal vertebra* (sloping
about 45®) are supported from the hypurals.
The hypurals are
visible through the caudal muscles* the,caudal, fin rays ar*
symmetrical, however, with respect to the body arts.
tail'has lost its lophoceroal character and is now slightly
The remnants of the fin. folds ar* still intact
but have %uite degenerated la parts,
there, is now a complete
separation between the adipose and dorsal fiasf likewise,
between the adipose a»A caudal fin, but.the dorsal flu Is
yet continuous with the anterior portion of the unpaired fia
fold! the dorsal fim fold disappears in the antero-posterlor
The ventral fin fold is still complete as in the
true, larval form.
FingerH a g s
By the- time the young fish has reached 35 mm. in length,
it has practically assumed the adult fora; all fins are
'fully developed except that the tail is shallowly forked (fig. 34} •
The head tapers forward so that the snout has
lengthened and become pointed and compressed! the eyes are
n©w rounded*.
The interrorbital area has somewhat expanded
iaterally^ and'the eyeballs, have sunt so that they are level
with the general surface of the sides of the head.
operculum has few but large melaaophores.
The pigment spots
on the abdomen, noticeable in earlier stages have sunk deeper
Into the underlying' musculature so that they disappear from
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tU v
except in two linear rows ©long the ventral wall from
anterior to the pelvic fins to the tip ©f the isthane, be­
tween the branohiostegal®.
The dorsal side of the body fro®
the snout to the tail is nor® densely pigmented.
the stelaa-
ophore® behind the anus and on either side of the anal fin
are .still conspicuous hut will disappear some tine before
sexual maturity is reached*
The caudal fin Is also pigmented
hut the asymmetry of the last few caudal vertebra© is a®
longer apparent externally end the type of the tail Is now
■perfectly homoceroal* .
Although the scales thus far have not. made their appear­
ance in the young fish, on the other tend has already
developed rhomboid scale pockets*
pockets are not apparent*
At If mm* length, these
Intermediate.lengths between IS
mm* and 34 m * are lacking from which to determine the exact
length at which the pockets appear on the skin*
Seales were
actually taken for the first time in 5.5 cm* fingerlings
In spite of the advances noted above (35 mm.) in. the
differentiation of the anatomical structures of the young
smelt, which are essentially of the adult type, pigmentation
still remains larval in character*
Thus from this time on
subsequent external.changes are concerned primarily with
the modifications and'development of adult pigmentation.
series of young fish illustrates the progressive soup is it lorn,
of the adult pigmentation.
From the figures one will, mot lee
that the process consists of the gradual spreading of the
melanophores throughout the ©stir© length:of the body on the
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dorsal side ventrally toward the lateral line.
At the tarn#
t l M a hand &t pigment, started as a mere streak and -superImposed upon the lateral line, gradually appears ant widens
as It makes its way/anteriorly, where it finally stops at' ,
stout, the posterior level of the ©paroles.
completed, the -young' fish leaves its post larval life and
assumes Its adolescent existence.
At this time the young
smelt is morphologically adult la appearance hut -la yet sex*'
mally immature fflgs. 84 and 3 }•
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!® ®
4* O
1 m«
ts «
® ea
*4 £••**»
• sfr*
P i
“ i.SS5
#>*it 8
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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Spawning season at Sapl® Grove is from May to October;
greatest activity Is July to August, diminishing In intensity
from September on*
Spawning set lasts but a few seconds. .
Size limits of tbs spawning population range from.
@•1 cm. to 17.3 cm.; spawning population consists of 3 year
classes* with the 2-year class dominant In number; life cycle
is completed in 3 years; no specimens older'than 3 years were
Scales appear on the body of tbs young flab at
lengths of §.§ to i.8 cm; shape of scales depends upon the
location on the body; scales are easy to read and are valid
criteria employable in age determination; evidence indicates
that anmuli are formed ■during winter.
Gonads in both sexes are a symmetrical,, the left mem­
bers in both being much larger than those in the right..
count increases with the increasing length of the fish.
tilization is immediately followed by water absorption; in­
crease of diameter of eggs due to water absorption is 18.4
per cent.
First segmentation is completed in the first two
hours after impregnation; rat© of cleavage is inversely pro­
portional to temperature; incubation period to hatching time
varies from Eli to 24© hour®.
'latching la probably both mechanical 'and chemical la
nature, with mechanical factors playing a greater rile*
larvae ar® positively phototrople, postlarvae are
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negatively phototropie; examination of stomach content shows
postlarva® ascend rivers ©r sloughs to feed,
At 7 cn. or thereabout, the finger!lug smelt ia
truly adult in all essentials except for Its being: immature.
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Agassiz, A* and 0. -0* Whitman
1884* On the development of some pelagic fish eggs.
Preliminary notice. Pro©*, Amer. Acad. Art© and
Sciences 20:23-75, 1 pi*
.Andre, 1* 1*
1875* Sur 1® preparation dm mieropyl® dans 1© eoque
des oetifs de trulte. lour. Anat. Physiol* 11s
J&atstrong, P* B*
1936. The mechanism of hatching In Fundulus hateroclitus
Biol*- Bull. 71:407.
Baudelot, M. 1*
1873* iecherches sur la structure et le developpeaent
das ecailles des polssons osseux. Archiv. Zool.
Sxper. et Gdner. '2:87-244 and 429-480*
Berglct, p, and P. Wintrehert
. .
1926. Le ddterminieme de l'eclosion chez l*Alyt©
(Alytes obstetrleans. Laur.l. Comet. Rend. soo.
B r a r w n s P l w r i fig©.
Bigelow, 1. B. and ». W. Welsh
■1928* Pishes of the. Gulf of Maine. Bull* 0* S. Bar*
fish. 40, pt* 1, 567 pp., 278 fig®*,
Blending, if.
1842* Fecundity of the ©tripe bass.
Sci., say* 1, Ju5f»
Proc* Acad* Hat.
Bloch, M. B.
1796* L*eperlen d'eau douce. Ichthyologie ©a SiatcLr®
Haturelle des foissons, pt* 1:244-247, i fig©.,
1 pi. a Berlin ©haz 1*Auteur*
Bogucki, M.
1930* lecherche© sur la permdabllitl de® membranes at
our la pression osmotlque de© oeufs des Salmoaides
Protoplasm© t(3)s345-369, 13 tables, 4 text fig®'.
Beard la, W*
1926, Le aecaniaae de 1 *©©!©© lorn chez les teleosteens.
C€»pt. Rend. Sc©. Biol. 95:1183-1186. 2 text fig®.
Brown, A* 1.
1904. Some observations on the young scales of the cod,
haddock, and whiting before shedding. Proc. Roy.
See. 24:437-438*
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
P. L.
1 9 4 0 Development of the egg® ami early k m » of six
California fishes. Blv. Fish and Game, State of •
California, fish Boll. Wo. 56, S3 pp., 91 fig®.
In 13 pis.
The life history of heuresthes tennis, an abherlm#
fish with tide control spawning'1'Sills..- Fish and
Game Comm., State of California. Fish Ball. Ho.
. 1 0 , 51.pp., i tables, § graphs, 4 pi®.
Greaser, C. I* •
1926. The structure ant growth of the scales of fishes
in relation to the interpretation of their life
history, with special reference to the sunfish,
Hupomotis nihhosna. Univ. Hlch. Una. Zool.
! ? :l-®2, 1 table,. 12 flga., 1 pi.
Cunningham, J* T.
1885. The significance of tapffer*s vesicle with remarks
on other questions of Vertebrate morphology,
tuari. I’
omr* iioros... Scl*, n.s* 25:1-14, 1 pi.
Dana, is.
lumber of eggs la Oadidae.
©©asm., 4;76.
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1894* Beitrage zur Haturgesehichte einiger Ubefisehe
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1815. Ichthyological motes on:
'' Obblofloa elongates Girard
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Isyes* ?• R
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Snatemaa, A* 8 *
1918a flit growth, of the » m I m
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la flakes, Trahs. toy.
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og n s k * m l T . I . M e g S a l e ns ISdre l # eg landers
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' It14.
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1868. BBeebeehtongen_uber
4* Satwiekeluxig 6* Knochene©
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1864* Seeherebes ear la. dtveloppensat 6a Broohet, de­
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the spawning p m of the Paoifio surf smelt,
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' lii&.
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IfeOay, 0. M. '
'* ■
1936* Inside inforaatiea concerning egg hatching. Fieh
Culture Bureau* Fish Guitar©, Hew York State
Con®. Dept. Albany, S* Y.’, Oet. 1936.
Meek, A.
The scales of the herring.and their value as. an
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',rr;: nL;",irr:....1
1 ... 1
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Ryder, S.
Samuels, S
Natural history of the Qp&asat salmon* Bull. 5. S.
fish Comm'. 22:65-141, unnumbered table®, # fie.
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1936. Contribution to the life history of the surf smelt
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1934* Sarly life history of the Cs 1ifornla sardine Saf **
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1916* Tie structure end growth of tie scales of squetsagu*
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1919* Tie egg production of tie halibut of tie FeeIfla*
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The scientific Investigations of marine'fisheries,
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"awallelle In::th®’
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TJssow, S, A. ■
1897. lie Sntwiekelung der Cycloid-Sehuppe fier Teleostler.
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1929. life history of the lake herrimr (Leuelebthys artedl
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with a ©ritlfue ©f the seal® method. Bull. U. S.
Bur* -Fish., M{10§3):20$»428f 64 tables, ,43 figs, .
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Observations on ovarian ova and follicles in eertain teleoste&n and elasmobraneh fishes. Quart.
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19124 Le meeanisme de I ’eolosion ohes la truibe arc-en- .
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1936. Structure of the trout egg. Fish culture 2(11)'
■1*15. .lew. fork State Cons, Sept. Bur. Fish-'
Culture, Albany, 1, T.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
i m
YAP- CHIGBUC0 was born on July If, If04 In
Allege, Nueva Icija» Philippines,
Francisco ant fomasa Terde.
la is the son ©f
Ha started hi® schooling
in his native town but finished hi® high school course
at the University High-. School., at Manila in 1985*
In the
same year he;.enrolled at the- University'of- the Philippines,
obtaining the degree of Bachelor of Science in Zoology la
In 1930, he was -taken assistant instructor la
Zoology, which afforded him a chase© to pursue graduate
le obtained the degree of fester of Science in
In 1937, he was made instructor in Zoology and a
year later was appointed Fellow of the University of the
Philippines to the United States.
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