Bull1Iss6ArtIV


THE FIR '£ FOOD OF THE COMMO WHITE-FI H. 

( REG J: L PEIF RMI , :Mit h.) 

BY . A. F RBE . 

In a very large lake the ondition of lif ar remarkably uni­
form. The v lume of wat r r main , of our , n arly 1 tant 
from season t eason and fr m year t y ar, and th extr m f 
ummer heat and winter c ld hav but a mod rat ff ct upon th 

t mp ratur of the lak a a wh le. n quently b th plant 
and animal lif exhibit th r a r gularity an 1 tabilit whi h ar 
in remarkable contrast to their fluctuati ns in mall r b di f 
water and on the surrounclin land. ot only do the r lativ 
number of individuals in th various p ci s r main al ut th 
ame, but th absolute number of a h mu t nece arily hang 

but little, a a rule. 
Such a tate of affair i eminently £av rable to an xact an l 

conomica,l balance of ·upply and l man<l, of income and x­
penditur , of multiplication an l cl truction, among th inhabit­
ant of the lake. Her , very speci s of animal, wh th r r cla­
ceous or v g tarian, mu ·t fincl, in the urplu product f r w-'-h 
and reproduction among th pecie · up n whi h it d p nd · f r 
food, a far more constant and unvarying upply for its n l than 

lsewhere; and th speci s f d upon mu t be ubj ct t a far 
more reo-ular drain upon th ir urplu numb rs ntial 
structure . Wb r th re i little flu tuati n th r i littl " wa t . 

A ystem of life lik this, runnino- on with r lativ ly v n t n r 
for centuries, must of c urs be mu h 1 s fl . ·i'bl than n wh r 
wide and vi 1 nt f:luctuati n and ntinual r adju tm nt ar th 
rule; and a pecies in any way cl ply aff ·ted will h r 
have within itself far l ss r up rative p w r than on whi h ha 
been forced ao-ain and a ain - a h ar, p rhap - t rall 
against the most d strn tiv atta k a th pri f it c ntinu d 



96 The First Food of the Common White-Fish. 

existence. Disturbances of the natural balance of life, of the 
primitive and spontaneous system of reactions by which the dif­
f rent groups of organisms are related, will therefore be unusually 
serious and lasting; and where such disturbances result fr m 
human interference, as by the yearly capture of large numbers of 
any important fish, it is especially desirable that artificial means 
of compensation be taken to restore the disturbed balance as 
nearly as possible. Excessive loss will be made good by natural 
reactions far more slowly than if it occurred to a pond or river 
species, accustomed, as most of the latter are, to fill up rapidly 
enormous gaps in their numbers. 

On the other hand, to multiply unditly by artificial measures any 
species naturally abundant in such a lake, will have scarcely a 
less disturbing influence than to diminish its numbers in the same 
ratio. The relatively nice balance between the demand for food 
and food supply which here naturally obtains, is such that an ex­
traordinary increase in a species must soon react to diminish 
greatly its food resources- a fact which will then take effect on 
the species itself, reducing it below its natural, original level; 
and if both excessive capture and excessive multiplication go on 
side by side we shall have this result finally aggravated to an ex­
treme degree. 

As fishes are caught before the end of their natural lives, but 
planted by the fish culturist when young, it is evidently the food 
of the young which will be first and most seriously affected by 
over-production. Only a part of the adults, perhaps a small frac­
tion, will live a life of ordinary natural length, many being cap­
tured before they have attained even the average size; but a far 
greater number, perhaps nearly every one, must survive the earli­
est period and must consequently draw most heavily upon the 
earliest food resources of the species when these differ from those 
of the adult. 

The above considerations are brought forward here to show the 
especial importance, to us, of a study of the system of natural 
interactions by which the animals of our great lakes affect each 
other, if we would avoid the necessarily injurious consequences of 
our own interference with the natural order there obtaining, and 
above all to show the extraordinary value of a knowledge of the 
food habits and food capital of the yoimg. They apply perhaps 



Th Fir t Food of the o,nmon TVhite-Fi.·h . 97 

1 · to th whit -fish than to any h r ·p' ·i' · m th 
lak thi i f r · v 'ral r a n th m ·t imp rtant pur 1 
fr h-wat 'r fi h f th gr a lak r gion, and prov · t ha.v a dis­
tinct! · Lliff r nt f ocl ,vh n 'Om\..; from that up n wlii hit i cl -
p --ml ut lat r. 

A r lino- t the r nt r port·* m r 
on milli n poun 1 of whit .-fi h w re tak n in th 

valu d at ov r thr -quart r of a milli n of d llar , and 
nti.ng 11 arl half th t tal um cl riv c.1 from th lake :fi ·h-

n fall kind . Th fi h ries mploy over :fiv th u ·an l men, 
and a fix cl apital f n milli. n thre hundr d anc.1 £ ry- ix thou-
and dollar . , h n w r fl •t that thi n nnc u · clrain up n th 

numb r f th p i i · n 'e · ·aril · to a n i 1 •rabl xtent an 
a k1iti n t the natural tax 1 vi c1 up n it b it· th r than 
man w that th re nm t b an arti.fi ial upply pr id 1, or 
th fi h ri · will oTadually fail. 

Th importan of the knowledo· of th fool f valuable a 
p i d no d mon ·tration sp ially wh n w onsider that, 
on i t ntl with what ha· be n aid abov , it may not be diffi­

cult to overdo the work of pr pagation. 
If the wbite-fi h w re t be multiplied ind finit •ly, with ut any 

att ntion to th hara t r r al umlanc of it fo 1 upply, it 
w ul<l soon reach u h a number that it must infrino· upon its 

wn food apital c.limini h th aYerage numb r of th animals 
upon wbi h it lepend for nb i t nc , and :finally imlire tly 
cri pl it. ·elf. Then th rn ncy and labor xp nd c1 in its culture 
woulc.1 b principall lo t and the lat stat" of th spe i s w uld 
b w r than the fir t. An acquaintanc with the foocl of the 

ung i pecially ne cs ary b cau e th ·y ar planted by th 
fi h- ulturi t when ha ing already ab orb 1 th o-g-sa (the up­
pl · f fo d by whi h th y are und r natural c ndition npportcd 
until th y lrn,~e time to catt r tit ms lv ' , id ,}y through the 
wat r), th y are in a p' uliarly h •lpl s·· oncliti n, unahl t wan­
d r far in ear h of ·ub.·i t n , a.n 1 · mp 11 tl t find foo 1 
p ~ dil or peri h. n woul 1 sa,y ther •fore that their alimen-

tary r ourc an l habit ·h uld b' ,, 11 and thorou:::-·hl known, 
that th range p rio 1 and abundan of th orgam ·m upon 

Bulletin o. 261, ept. 1, 1 1. 



98 The First Food of the Common White-Fish. 

which they feed should be carefully determined, and that each 
locality where the young are deposited should be closely searched 
for the purpose of ascertaining whether their food species occur 
there at the time in sufficient quantity to prevent immediate star­
vation. 

Previous studies of the food of young fishes of a variety of fam­
ilies, reported in the third Bulletin of this series, had showed that, 
with exceptions presently to be mentioned, the earliest food of all 
the families studied consisted almost wholly of. various species of 
Entomostraca and some equally minute and delicate dipterous 
larvre. When that paper was prepared, I had, however, no oppor­
tunity to study the food of the young of any members of the family 
Salmonidre, to which the white-fish belongs, neither could I learn 
that any such studies had been made by others; and I could only 
infer the same fact with regard to this family from the general 
character of the results obtained by the study of the other groups. 
Even this inference, however, was rendered doubtful by the dis­
covery that the youngest individuals of two of the toothless fami­
lies (Catostomidre and Cyprinidre) were not strictly dependent 
upon the food elements a ~ove mentioned, but were likewise able 
to draw upon much smaller organisms, namely: the minutest 
Protozoa and unicellular Algre; and as the adult white-fish is like­
wise destitute of teeth, it was not by any means certain that their 
young would not fall under the latter category. Upon looking up 
the literature of the subject, I found that although the food of 
the adult had been very well made out in a general way,* only 
two items had been published respecting the food of the young. 
In the report of the United States Fish Commission for 1872-3, 
an assistant commissioner, Mr .. J. W. Milner, made some experi­
ments on young white-fish hatched -artificially, supplying them 
with a number of articles of food, in the hope of :finding some­
thing suitable for their nourishment. 

"A few crawfish," he says, "were procured and pounded to a 
paste, and small portions put into jar No. 1; the young fish ate 
it readily. They were fed at night, and the next morning every 
one of them was found to be dead. Jar No. 2 was supplied with 
bread crumbs, and the fish were seen to take small particles in 

*Report of the U. S. Fish Commission for 1872-3, pp. 44-46. . 



The Fi,· t Food of th ornmon TT7iite-F' h. 9 

th ir m uth · th y litl n t di .Jar .... 3 wa up-
pli d witn weet r am but n id n wa a:ff rd d that h 
o ·upant fe l upon it. quantity f rain-wat r wa xp cl t 
th ra · f th un f r th purp ., f g n ratin, minut form 

f lif and a t a-p nful wa p ur lint jar . 4 rn r · nc1 

eY nino- in th hop that th ir Ir p r f od wa f thi r. 

In jar . 5 a ntri t · of fool wa pr vid l dr, fr ·h b f mill , 
boil cl potato and br a 1. The rumb f br ad an l th raprn r 

from th~ b f w r all hat th fi ·h w r · en to tak int th ir 
m uth . Th y <liet1 on aft r an th r , r rapicll · and in a f w 
t1a y all were dead. H forth r r mark : ' Thi. diffi ult f 
pr urii1_:., a uitable fo d f r th young whit -fi h ha b n th 
exp ri nee of the f w :fi h- ulturi t wh hav hat bed th m. ' 

Y\ ith th hope of a c rtaining the natura l fool of th 
a few pecnuen r pr ntin youn captured in th 
Riv r an l other from th hatch ry, " re ubmitt l b 
ner to ~Ir. . A. Brigg a micro c pi t, of '1hi aao. 
ple w re examin cl b ~Ir. Brigg , tw from a h 
ituati n . Tho e from th hatcher ontained n thing what v r, 

whil tho e from D tr it River ontain cl mun r u p im ns of 
of Diatoma , Yiz. Fl'ayiluria capucinu anc1 ;_'t >,pfi­

wwdi'Clf' niayar e. Th only fact at that time kn wn would 
con equ ntly incli ate that th arli t food f th p i n i t d 
of Diat macere . 

Th whit -fi h as is well known, lays it gg in th op n lak 
in autumn the youno- not appearing until arly in th f llowing 
prmg. t tbi old an 1 tormy ea on in th expo. l ituati ns 

wh re the are to be ought it i practicall impo il le t :find the 
youn :fi h; a fact which rendered th tudy ~f th ir arli st food a 
subject of unu ual liffi ulty. Ther m d, in fa t, n practica­
ble wa to r acb ati fa tory conclu ion· upon it x pt by xp r ­
irnent upon individual artificially hatch cl. 

In Decemher, 1 0 I mad an arrang m nt, thr u h th kirn1-
ne of Pr f. Baird, of th mith onian In titution, with Jr. F. 

lark, up rintend nt of th . fi h hat h r. a,t rthvill , 
Mich. for a upply of youno- white-£. li to l sent m at interval 
from th hatchery un l r hi contr 1. Th pe im n furni he 1 
were taken from two lot.. The fi b of n lot hat h c1 .J anuar 
1 were k pt in a tank in the hat h r , wh r they w r upplied 



100 The First Food of the Common White -Fish. 

with water from a spring, which had been cooled by exposure to 
the air in artificial ponds before entering the hatchery, in order 
to retard the development of the fry. The ordinary range of 
temperature in the tank, was from thirty-five to thirty-nine de­
grees. These fishes were fed daily with a paste m::tde by grinding 
small amphipoq. crustaceans (Gammarus) in a mortar. 

The second lot, hatched January 20, was kept, unfed, in a per­
forated tin box, in a rivulet flowing from a spring, about sixty feet 
from its source. The water had a uniform temperature of forty­
seven degrees. 

Those in the spring being in warmer water than the others, de­
veloped much more rapidly, and it was believed that the character 
and source of this water was such as to furnish them at least a 
small supply of such food as young fishes are accustomed to ap­
propriate. 

Ninety specimens were received from the hatchery February 9, 
at which time they were three weeks old. They were thirteen 
mm. (half an inch) in length by one in depth. The egg-sac was but 
partially absorbed in . most of the lot, but in those most advanced 
was represented by an oil globule back of the head. The pectoral 
fins were well developed, but no trace of the ventrals had as yet 
appeared. The single median fin extended well in front of the 
vent, and forwards on the back nearly to the head. The opercles 
did not fully cover the gills. The most highly developed spec­
imens - those whose g ill-sacs had nearly disappeared-had, at a 

short distance on either side of the symphysis of the lower jaw, 
a sharp, strong, raptatorial tooth, curved backwards and slightly 
inwards. The base of this tooth was very broad, and the point 
acute and slender. At a point behind each of these teeth about 
half their distance from each other, was a second much smaller 
tooth, directed almost exactly inwards. The upper jaw was, how­
ever, wholly toothless. 

These fishes were all passed under the microscope, after having 
been rendered transparent, but only four of them contained any­
thing whatever; three a little dirt, and the fourth a minute frag­
ment of the crust of the Gammarus, with which they had been 
fed. 

Of one hundred and eleven specimens received February 17, 
seventeen had taken food. I dissected nine of these and found 

• 



The First Food of the Common White-Fish. 101 

fragm nts f Gammarus an l nothing el . Nin ty spe im n 
from the same 1 t w r xamin cl Febru:iry 25, an l food was 
found in fourteen. Four f th had eat n Gammaru fraD'­
ments; two, larvre of gnats; n , a small Cypris, and ight c n­
tained small fragments of the 1 av and t ms of va cular plants, 
including a bit of a nett d-v inecl leaf and a littl pi c of pine 
wood. Thirty-nine sp cimens, the la t of th ]ot, wer r c ived 
Iarch 15, and food was found in fourteen. I di ct cl nine of 

these, findina fragments f Gammaru in four, a larva of a gnat, 
a hiron mns larva, a larva of some undetermined fly, a minute 
vegetable fragment, a Cyclops, a Cypris, and an undetermined 
Ent mostracan each in one. Three hundred and forty fry fr m 
the hatching house were examined in all, in forty-sev n of which 
(fourteen per cent.) mor or les food was discernibl . Of the 
thirty-five dissected, eighteen ha l eaten Gammarus fragments; 
five, minute insect larv ; four, Entomostraca, and ight, small 
particles of vegetation. 

Only four lots were re eived from the spring, on th 9th, 14th, 
l 7tl1, and 25th of February, after which all died of starvation. In 
the first hundred only one was found which had taken food, and 
this had eaten a trac of filamentous Algre and a minute fragment 

f the parenchyma of some higher plant, with a few diatom·. 
But one of the second hundred contained even a trace of food, a 
minute quantity of some thread-like Alga, the cells of which still 
contained a little chlorophyll. In the third hundred likewise, food 
was found iu but one. This consisted of a few particles of veget­
able parenchyma, doubtless derived from the decaying plant stru -
ture in or around the wat r. In the third lot of only forty-two 
specimens, six showed traces of food, consisting almost entir ly of 
a few filamentous Algre (including a fragment of Oscillatoria) and 
a little vegetable parencbyma. Desmids and diatoms were ob­
served in trivial numbers. 

The total number received from the spring was two hundred 
and forty-two, of which but eight were found to have aten any­
thing (a little over three per cent. of the whole), and these had 
taken only Algre and vegetable fragments. 

An example of the water of the spring s nt me contained many 
Algre but no animals larger than rotifers. The water of the 
hatchery, being expo ·ed in pond: of consid rable size, afforded a 



102 The First Food of the Cornman White-Fish. 

better opportunity for the development of animal life, to which 
fact was doubtless due the_. occurrence of insect larvre and Ento­
mostraca in the intestines of the fishes reared in it. The situation 
of the spring, on the other hand, was particularly unfavorable, as 
it was under the hatchery, and consequently in the dark. 

The observations above described on the specimens kept in 
spring water, have but littl e value for the reason that evidently 
very little food was contained in the water flowing through their 
cage. The vegetation in the streams being chiefly filamentous 
Algre and the number of Entomostraca apparently trivial, very 
little of either vegetable or animal food could reach the little 
prisoners. It is not surprising, therefore, that notwithstanding 
their greater age and the higher temperature of the water in which 
they were kept, a much smaller ratio of the specimens had taken 
food than of those captured in the hatchery. From the contents 
of their intestines we can only infer that these fishes, reduced to a 
desperate strait by starvation, will snatch at almost anything con­
tained in the water. The result obtained by a study of those from 
the hatching house was more significant, but still unsatisfactory. 
It seemed to indicate that in confin'ement white-fish fry will feed 
upon both animal and vegetable structures to some extent, and 
that they can be induced to take minu

0

te fragments of the higher 
crustaceans, but not in sufficient quantity to keep them alive. 
The fact that animal food was more abundant than vegetable in 
this last lot, indicates nothing of their natural preference, since it 
was doubtless also more abundant in the wate containing them. 

More light was thrown upon the earliest food habits of these 
fishes by the discovery of raptatorial teeth upon the lower jaw, 
than by these dissections of their alimentary canals. All the fam­
ilies of fishes which I had previously studied whose young were 
provided with teeth were found strictly dependent at first upon 
Entomostraca and the minuter insect larvre; while only those 
whose young were toothless fed to any considerable extent upon 
other forms. The discovery of teeth in the young white-fish, 
therefore, placed this species definately in the group of those car­
nivorous when young. The fact that the adult was itself tooth­
less interfered in no way with this inference, because other tooth­
less fishes (Dorsoma) whose young were furp.ished with teeth, had 
been found carnivorous at an early age. 



The First Food of the omrnon White-Fi h. 103 

The in on lusiY hara t r f th re ult thu far 
it n c ary to attempt to imitat mor . closely th 
ti n of the younrr when hat h cl in the lak . ln 
I obtain d throuah the kim1n of Mr. larke tw 

btaiu cl, ·made 
natural i-
bruary 1, 

V p 1-

men of livina oung white-:6 h av <l from a lot h , a 
plantina in the wat r of Lake "i\Iicbiaan, off Ra in , "\ i on in. 
I uccee led in conveying- th t the lab ratory with ut lo , an l 
th r k pt th m for s v ral cla in a ala aquarium an l suppli d 
them with an abun<lan of th li ina objects to be obtain d b 
drawina a fine muslin n t thr ugh th tagnant pool of h 
vi init . The e con i ted f man · lliatom and filam nt u fr h­
wat r lgre, of two or thr e p ci f Cyclop , f 'rrntlwco mp-
tu' illinois ,i is, and Diaptomw; wzguin us amona th op p da 
and of two rather large Cladocera inwceplwlu · v tulu an<l '. 
mnericanus. The e littl £.sh s were kept und r careful obs rva­
tion for everal day , th wat r in the aquarium beina frequently 
aerated by pouring. Iany of them had, however, been injured 
by handling, and eleven of th specimens di d with ut taking 
f otl . It wa oon evident that th laraer Entomostraca (the im­
ocephalu , and even the Diaptomu ), were quite b yoncl th siz 
an l trength of the e little fi h , and that only th maller Co­
p poda among the animal available, could afford them any fool 
at fir t . The e they followed about from the beginning with sign 
of peculiar •intere t, occa ionally making irre olute att mpt t 
capture them. Two tla aft r th ir arrival one of th young 
whit -fi h had evidently taken f od, which proYed, on di e ti n, 
to be a small yclops. During th next two day nine oth r · b -
gan t at, cfo-iding their att ntion between the ydops ab ve 
m ntioned and the anth am1 tu , an l on th 22d two oth r 
took a yclop ea h an 1 a third a ant~1ocamptu . On of th · 
fi h ontained till a Jar r mnant of the ega- ac, showing that 
th propensity to a,ptur pr mu t antedat th ensati n f hun­
g r. On the 2- th the fomt nth and last rema~nino· ti h aptur <l 
it Cyclop and wa it elf a rifi ed in turn. s an in<licati n 
of the efficiency of th raptatonal teeth, it may b worth whil t 
not that I aw one of th mall st fi he make a ·priua at a Cy-
lop , catch it, giv thr e or four violent wriggle , a1 cl drop it d ad 

to th bottom of tank. 
A a general statement of th r . nlt of the oh ·ervation made 



104 The First Food of the Common White -Fish. 

on these fourteen fishes, we may say that eight of them ate a sin­
gle Cyclops each, that one took two, and another three of the 
same, that one took a single Canthocamptus, that two specimens 
captured two each of this genus, and that finally, a single fish ate 
Cyclops and Canthocamptus both. The final conclusion was a 
highly probable inference that the smallest Entomostraca occur­
ring in the lake would prove to be the natural first food of the 
species. 

In order to test this conclusion with precision, I arranged a sim­
ilar experiment on a larger scale and under more natural condi­
ditions. Through ~he generosity of the Exposition company, of 
Chicago, I was allowed the use of one of the large aquarium tanks 
in the exposition building on the lake shore, and by the repeated 
kindness of Mr. Clarke, of Northville, Michigan, I was furnished 
with a much larger number of living white-fish. Five thousand 
fry were shipped to me in a can of water, but through unfortunate 
delays in changing cars at intermediate points, about two-thirds 
of these were dead when they reached my hands. Those living 
were immediately transferred to the tank, through which the 
water, taken from the city pipes, had already been allowed to run 
for several hours. As this water is derived from Lake Michigan 
at a distance of two miles from the shore, and had at this time the 
exact temperature of the open lake, the conditions for experiment 
were as favorable as artificial arrangements could well be made. 

Sending a man with a towing net out upon the lake with a 
boat, or upon the remotest breakwaters, immense numbers of all 
organic objects in the water were easily obtained. After enclosing 
the exit of the tank with a fine wire screen, to prevent the escape 
of objects placed in it, we poured these collections of all des~rip­
tions indiscriminately into the water from day to day, thus keep­
ing the fishes profusely supplied with all the various kinds of food 
which could possibly be accessible to them in their native haunts. 
From this tank one hundred fishes were taken dailx_ and placed in 
alcohol for dissection and microscopic study, to determine pre­
cisely the objects preferred by them for food. These were ex­
amined at a later date, and all contents of the intestines were 
mounted entire as microscopic slides, and pemanently preserved. 
A careful study, was of course made of the organisms of the lake, 
as shown by the ;Product of the towing net, and when the experi-



The First Food of the Common White-Fish. 105 

ment wa finally end d, an equall car ful examination f llow d 
f the liYing contents f the water of th tank at that tirn . 

Th se :fi hes, like those previously describ 1, had alread 
rea h d the ag an l ondition at which it is cust mary to "plant" 
th m in the lake. The ventral were still und , elop d, the egg-
ac bad nearly di appeared, the four mandibular teeth were pre -

ent, and the median fin extended from the tip of the p ctorals on 
the b lly to a point oppo ite the midclle of the same fins on th back. 
In most the egg-sac did not protrude externally, bein reduced in 
som to a droplet of oil, but remaining in a few of a size at least 
as great as that of th head. The alimentary canal was of course 
a simple straight tube, without any distinction of tomach and 
inte tine. 

The su:ff ring of th fry in tran it had doubtless weakened the 
vitality of the urvivors, and alth ugh every are was tak n to 
keep the water of the tank fresh and pure, about one-third of 
those remaining died during the progress of the experim nt. The 
aquarium in which they were confined was built of glass, and 
had a capacity of about one hundred cubic fe t. The tempera­
ture, tried repeatedly, stood at fort -two degree Fah. A steady 
current of the water of the lake was maintained through this tank, 
entering through a rose, from which it fell in a pray, thus insur­
ing p rfect a'>ration. 

By far the greater part of the organic contents of the water of 
the lake, as shown by the product of the towing net, consisted of 
diatoms in immense variety, which formecl alwa3 a greenish mu­
cilaginous coating upon the interior of the muslin net. In this 
were entangled, a variety of rotifer , occasional filamentous Algre, 
and many Entomostraca, the latter belonging chiefly to the genera 

yclops, Diaptomu , and Limnocalanus among the Copepoda, and 
to Daphnia among the Cladoc ra. 

As the Entomostraca proved to be far th most important ele­
ment of this food supply, the particulars re pecting them may b 
properly more fully given. The small st of all was a Cyclops, 
then new, but since described by me under the name of yclop<.: 
thomasi.* This little Entomostracan is only .04 inch long, by .011 

i;,on some Entomostraca of Lake Michigan and djacent Water . 
American Naturalist, Vol. XVI., o. VIII, Augu t, 1 2, pp. 6--!0 and 
649. 



106 The Filrst Food of the Common White-Fish. 

wide. The next in size, and by far the most abundant member of 
this group was a Diaptomus, likewise new, described in the paper 
just cited under the name of Diaptomits sicilis. This appears in 
two forms, one evidently young in the stage just preceding the 
adult. Full grown individuals were .065 inch long, by one-fourth 
that depth. The Limnocalanus was a much larger form, evidently 
preying, to a considerable extent, upon the two just mentioned. 
All the Cladocera noticed were D ciphn:ia hyal-ina, an elegant and 
extremely transparent species, occurring likewise in the lakes of 
Europe. A single insect larval form (Chironomus) should likewise 
be mentioned in this connection, since it had about the same size 
and c01~sistence of the Entomostraca, and was consequently equally 
available for food. 

The specimens of each of the above species from a certain 
quantity of these collections were counted, in order to give a defi­
nite idea of their relative abundance in the lake. The Diaptomus 
numbered 225, the Cyclops 75, Limnocalanus 7, Daphnia 3, and 
Chironomus larvre 1. It was a curious fact, however, that when 
the water was drawn off at the end of the experiment, more than 
half the Entomostraca were Limnocalanus; a fact partly to be ex­
plained by the predaceous habit of the latter, and partly by the 
facts relating to the food of the :fishes themselves, which are pres­
ently to be detailed. 

The fry were placed in the tank and supplied with their :first 
food on the evening of the 12th of March. On the 14th, one 
hundred specimens were removed, and twenty-seven of thes~ were 
dissected. Twenty were empty, but the remaining seven had 
already taken food, all Cyclops or Diaptomus. Three had eaten 
Cyclops only, and six Diaptomus, while two had eaten both. 
Fourteen of these Entomostraca, seven of each genus, were taken 
by these seven fishes. From. those captured the next day, twenty­
five specimens were examined, of which nineteen were without 
food. Of the remaining six, three had eaten Diaptomus and three 
Cyclops; five of the former being taken in all, and ten of the lat­
ter. Three specimens were next examined from those caught on 
the 19th of March, two of which bad devoured Diaptornus, and a 
third a single Cyclops thomasi and a shelled rotifer, Anwy,ea striata. 
The character o{ tl1e food at these earliest stages was so well set­
tled by these observations that I deemed it unnecessary to exam-



The First Food of the Common White -Fish. 107 

me the subsequent lots iu detail, but pa ed at once to the speci­
mens taken on the 23d. Twenty-six of th e were examined, and 
found to have aten }hirty-three individuals of Cyclops thomasi, 
fourte n of Diaptomus ie,ilis, and fourteen of the minute rotifer 
already mentioned (_,_-1:nw·cea <?t1'iata). Two had taken a few diat­
om (Bacillw·ia) and one had eaten a £lament of an A lga . Cy­
clop wa found in sixteen of the specimens, Diaptomus in nine, 
and Anurrea in eight, only two of them being empty. The 
amount of food now taken by individual fi hes was much greater 
than before one specimen dissected baying eaten two Cyclops and 
six Diaptomu ::;icilis, male and female. Another had taken five 
Cyclop ·, one Diaptomus and five examples of Anunea st1·i tta. 
Still another had eaten four of the Cyclops, four Diaptomus, and 
one Anurrea. 

Twenty-fiv•e specimens were examined from those removed on 
the 2-!th of the month, at which time the water of the tank was 
drawn off and all the remaining £shes bottled. Four of these had 
not eaten, but the twenty-one others had devoured fifty specimens 
of D iaptonws sicilis, forty -seven of Cyclop tlwmasi, fourteen of 
An:unea stn' lta, and a single D aphnia hyalina, the latter being 
the large t object eaten by any of the fi hes. A few exampl s of 
their capacity may well be given. T he ninth example bad eat n 
six Diaptomus, two Cyclop thomasi and one Anurrea ; the tenth 
had taken eight Diaptomus, two Cyclops and an Anurrea; and 
the twentieth, seven Diaptomus and three Cyclops th01nasi . 
I n two of these examples were small clusters of orange g lobules, 
probably representing unicellular Algre . 

Summarizing these data briefly, we find that of the 106 peci­
mens dissected, sixty-three had taken food, and that the ratio of 
those which were eating increased rapidly, the longer the fishes 
were kept in the aquarium. Only. one-fourth of those examined 
on the fourteenth of the month had taken food, whi le more than 
five-sixths of tho e bottled ten days later had already eaten. The 
entire number of objects appropriated by these sixty-three fishes 
was as follows: Cyclop thomasi, ninety-seven; Dittptomus sici­
lis, seventy-eight; 1nu1'cea st1'iata, twent3 -nine; Da1 hnia hyal­
ina, one. even of the fishes had eaten unicellular Alg::e, two 
had eaten diatoms, and one, fi lamentous Al ·re . 



108 The First Food of the Cornman White-Fish. 

From the above data we are compelled to conclude that the 
earliest food of the white-fish consjsts almost wholly of the small­
est species of Entomostraca occurring in the lake, since the other 
elements in their alimentary canals were evidently either taken 
accidentally, or else appeared in such trivial quantity as to contrib­
ute nothing of importance to their support. In fact, two spedes 
of Copepoda, Cyclops tlwrnasi and Diaptornus sicilis, are certainly 
very much more important to the maintenance of the white-fish in 
this earliest stage of independent life than. all the other organisms 
in the lake combined. As the fishes increase in size, vigor, and 
activity, they doubtless enlarge their regimen by capturing larger 
species of Entomostraca, especially Daphnia and Limnocalanus. 

A few words respecting the relative abundance of these ~pecies 
at different seasons of the year and their distribution iu the lake, 
will have some practical value. We may observe here an excel­
lent illustration of the remarkable uniformity of the life of the 
lake as contrasted with that of smaller bodies of water already 
referred to, in the introduction to this paper. While in ponds 
minute animal life is largely destroyed or suspended during the 
winter, the opening spring being attended by an enormous in­
crease in numbers and rate of multiplication, in Lake Michigan 
there is but little difference in the products of the collecting 
apparatus at different seasons of the year.* There is a slight 
increase in the number of individuals during spring and early 
summer, but scarcely enough appreciably to affect the food 
supply of fishes dependent upon them. They are not by any 
means equally distributed, however, throughout the lake, my own 
observations tending to show that there are relatively very few of 
these minute crustaceans to be found at a distance of a few miles 
from shor~, and that in fact by far the greater part of them usually 
occur within a distance of two or three miles out. Indeed, the 
mouths of the rivers flowing into the lake are ordinarily much 

'''For definite assurance of this fact, I am indebted less to my own ob­
servations (which are, however, consistent with it as far as they go) than 
to the statements of B. Vl. Thomas, Esq., of Chicago, who, while making 
a specialty of the Diatomacere of the lake, has eollected and studied all 
its organic forms for several years, obtaining them from the city water by 
attarhing a strainer to a hydrant many times during every month 
throughout the year. 



The First Food of the Common White-Fi.sh. 109 

more densely populated by the e animals than the lake itself, a· 
has b en particularly evident at Racine and outh Chicago. 1-

ther are they commonly equally distributed throughout the water 
in which they are most abundant, but like most other aquatic ani­
mals, occur in shoals. In the deeper portions of the lake 
many species shift their level accor liug to the time of day, coming 
to the surface by nio·ht, and sinking again when the sun is bright. 

These facts make it important to the :fi.sh-culturist that the par­
ticular situation where it is proposed to plant the fry should be 
searched at the time when these are to be liberated, to determine 
wbether they will find at once sufficient food for their support. A 
little xperience will easily enable one to estimate the relative 
abundance of the Entomostraca at any given time and place, and 
they require nothing for their capture more complicated or difficult 
of management than a simple ring net of cheese-cloth or similar 
material, towed behind a boat. This may be weighted and sunk 
to any desired depth, so that the contents of the water either at 
the surface or at the bottom, may be ascertained by a few minutes' 
rowmg. 

In conclusion, I wish again to express my great obligation to 
the United States Fish Commissioner, Prof. S. F. Baird, and to 
Frank N. Clark, Superintendent of the United States Hatchery 
at North ville, Mich., through whom, as already stated, the speci­
mens were derived upon which these studies were made. My best 
thanks are also due to the Exposition company of Chicago, and 
especially to their secretary, the Hon. John P. Reynolds, for the 
use of a tank in the Exposition building, and for many courtesies 
received while the experiment there was in progress. 



ERRATA. 

Page 6, line 12 from bottom; page 8, line 15; page 11, line 2; 
for Cyclniclce, read Pentatomidce._ 

Page 17, line 9, before Vireo; omit ancl. 

Page 23, above ARACHNIDA, for Cyclnidce, read P entatomiclce. 

Pages 25 and 27, above Orthoptera, for Cyclniclce, read P enta-
tomidce. 

Page 28, lines 2 and 8, for Graphorhinus vados1ts, read Epi-
cce1·us imbrricatus. · 

Page 64, under Hemiptera, for Siplwnophora granarice, read 
Aphis maidis. 

Page 69, line 5 from bottom, for jresh-wate1·, read local. 

Page 78, line 1, after all, insert the. 

Page 82, line 7, for cha1·acte1·, read charctcte1·s. 

Page 91, line 5, for consisted, read consists. 

Page 92, line 2 from bottom, for more, read most. 

Page 97, line 11, for f01·y-six , read f01·ty-six . 

Page 99, line 2, for witn, read with. 

Page 101, lines 12 and 13 from bottom, for stritcture, read 
structitres. 

Page 105, line 23, for aeration, read ae1·cttion .