ON THE FOOD OF YOUNG FISHES. 

BY S. A. FORBES. 

I ca11not lea1--n tl1at anything l1as been 1·eco1"clecl l"e­
specting the food of yom1g fishes in this cot111t1"3r, * 1101-­
l1ave I bee11 able to fi11d anytl1ing upo11 tl1is sl1l)ject i11 
sucl1 pa1·t of the ichthyological literatlll"e of Et11"0l)e as 
is accessible to n1e. F1"om the lack of all 111ention of tl1e 
11se of Enton1ostraca as the food of you11g fis]1e s i11 tl1e 
g·eneral revie,\7 of t]1e relatio11s of tl1ese C1·t1stac·ea to 01·­
ganic nat111"e gi,re11 by Gerstaeclce1" in B1·011n 's Tl1ie1"­
Reicht I infe1-- that ,,,.l1atever systematic in,Testig·atio11 tl1e 
subject may }1avTe recci,red, the results l1ave riot att1·acted 
any general atte11tion. 

This seen1s a s111·1)1"isi11g· fact \'\7 l1e11 011e co11sicle1·s t11e 
,rast amo1111t of labo1· ,,rhich l1as lJee11 expe11clecl 11po11 tl1i s 
class of ani111als, a11d 1"efiects fo1· a n1oment t1po11 tl1e i11-
terest to science ancl to p1"actical fisl1-c·ult111"e of a lznowl­
edge of tl1e f oocl 1--cso111 .. ces of fisl1es a11cl of tl1e co1npeti­
tions of the , ra1·io11s s1)ecies i11 tl1e sca1·cl1 f 01· s11l)~istc11re. 

Although I ca1111ot 3rrt t1·eat t]1is st1bject as f11ll~,. a s jt 
deserves, the 1"esu]ts of such st11cly as I l1a,,.e been al)le to 
make, duri11g tl1e past season, of the co11tents of tl1e stom- . 
achs and intesti11e8 of s111all speci111e11s, s<:e1n to j11. tif~r 
tl1is prelimina1"3T 11otice. 

It ,vas ea1"ly a1J11a1'e11t, i11 tl1c cou1"se o·f. tl1e i11,~cstiga­
tion, that tl1e foo<l of 111a11y fisl1es diffe1"s ~~·1·eatl,T accorcl-. ( . . 
ing to ag·e; and jt ,vas soo11 fo11nd that tl1e 1i£e of 111ost of 
our fishes clivides i11to at least two pe1"iods, and of 1nan)1 

into thr·ee, witl1 l"espect to the kinds of food chiefly take11. 
Further, in the fi1"st of tl1ese pe1"iods a remarl{al1le simila1·­
ity of food ,,Tas 11oticed amo11g species and fa1nilies whose 
later food-l1abits are ,videly diffe1"ent. 

:1< Perhaps exception sl1ould be 1nade of a note relating to tl1e occurrence 
of diatoms in the stomachs of two young whitefishes, published in the 
appendix to the Report of th0 U. S. Fish Commissioner for 1872-3, p. 57. 

t Classen und Ord11u11g·en dns Thier-Reichs, Band V, A1'1thPilung 1, ss. 
750 u. 1057. 

• 



• 

72 Oti the Food of Young Fishes. 

The full-gro,vn black bass, for example, feeds princi­
pally on fishes and crawfishes, tl1e sheepshead on mol­
lusks, the gizzar·d-sbad on mud and Algre, ,vhile tl1e cat­
fishes are nearly oninivorous; yet these are all found to 
agree so closely in food when very small that one could 
11ot possibly tell from the conte11ts of the stomachs ,vhich 
group he was dealing with. 

It is my purpose in this paper to g·ive what facts I have 
1"elating to the food of our fresh-,,rater species during 
this first 1)e1 .. iod of the fisl1 's life. These facts we1·e de­
I"ived from tl1e examination of one l1undred and twenty­
six specimens, ranging from th1"ee-eighths of an inch in 
length up to an inch and a half, and in a few cases to two 
and three inches. These specimens belong to t,venty-four 
genera and r·epresent eleven families. In two or three 
genera none vve1"e obtained small e11ough to be 1--ega1·ded 
as belo11ging st1,.ictly to this first food-pe1--iod, but the 
earliest food is 11evertl1eless plainl}r inferable; and the 
general distributio11 and var·iety of the species studied is 
such that I think the main conclusions will be fot1nd to 
stand the test of full i11vestigation. As the first pe1--iod is 
evidently mt1cl1 shorter ,vitl1 some species than with 
others, and do11btless var·ies in tl1e same species accord­
ing to situatio11 and circl1111stances generally, of course 
no com1no11 li111it o:f size cot1ltl be set up, but tl1e s1nallest 
specime11s of eac]1 species "'re1"e selected until a size was 
1·eac}1ecl whe1"c a ma1·kecl diffe1·e11cc of food a1)pea1"ed. 

Ac A N ,.rI-IOPTERT. 
• 

Althot1g·l1 tl1c 3rot111g 1\.ca11tl1optc1·i l1a ,Te al1·cacly bec11 
<11 sc11RSffl in t11c p1"ecccli11g 1)ape1· 011 t]1e foorl of that 
g1·c}up, it ,,Till l)r convenie11t tc) 1•(i,•ic,,T tl1c fc:1<1 t~ co11r~1·11-
ing t}1csc }TOlll].g fisl1es f 01· the p111·posc of co1·1111n1·ing· 
tl1ci1" f oocl ,,rit]1 tl1at of t]1c <)tl1e1-- 01·de1·s. 

T11c foof1 of six co11i111,rJ,,1 1Jft·cli (Pe1·c·(1 nJJl(1 J·i<'.G J/.(l,), 

J'1·01n c111 i11ch to a11 i11cl1 ::1:11cl ~t ql1ar·tc)1• l<>11g·, <'<)llHisL<."'<1 
,,,J1olly of E11tomost1·aca and la1·vrr of (111i1·onc)11111i-;- cig·l1t 
1><>1" cc11t. Cl1i1'01101n11s, fift)~- two 1><)1• c1<\11t,. ('ll,1 (l<> <' ' 1 t·ct ,111 \l 
f cJr·ty 11c1· cer1t. Copc1)oc1a. 



• 

73 

No ve1•)T small Lab:i;aciclre were fo11nd, tlJe youngest 
being a Mo1"011e an inch ancl a qt1arter long·. Ilalf of the 
i·ood of tliis consisted of Entomostrac·a ( c.l1iefl~~ Cla.doc­
e1·a), a11c1 the otl1er l1alf was minl1 te gizzarcl-s 11ad. 

A g·1·oup of f 01"ty-tl11"ee sl111fisl1es ( Ce11t1"archidre), from 
five-eigl1tl1s of a11 inch to t,,ro inches long, was made up 
as follows :-of five s1)eci.mens of M·ic1"opterus under 
t11ree-fo111·ths of a11 incl1 lo11g·, two A111bloplites of tl1e 
si1me size, t,,·o of Chre11ob1•)rttt1s fro1n se,,.en-eigl1tl1s of a11 
inch to 011e i11cl1, one of .L-\.pomotis an i11cl1 i11 lengtl1, nine 
of Lepiopo11111s from. a11 i11cl1 to a11 i11ch a11cl a four th, ni11e 
of Eupo111otis £1·on1 011e a11cl a 11alf to t,,To iucl1es, five of 
Cent1"a1·cl111s 011e inch a11d 1111cle1", fol11· of Pon1oxys f1"on1 
tl1ree-fol11·tl1s of a11 i11cl1 to a11 i11cl1 and a l1alf, a11d six i11-
c1ete1·mi11ablc speci111e11s, 1)1·obal1l~T Lepiopon1l1s, from 
seve11-sixtee11tl1s to :fi,re-eigl1ths of a11 i11cl1 long. Ninety­
six pe1· ce11t. of tl1e fooc1 o·f tl1ese f orty-tl1ree speci111ens 
consistecl of Ento1nost1--aca a11cl lar·,rre of Cl1ironon1us­
sevent:s,... of tl1e :fi1"st a11cl t,,Te11 t,,.-six of tl1e second-tl1e 

~ . 
t1--ivial 1·emaincle1· consisti11g of N et11"opte1"a larvre a11cl 
~Toung· ...:-\.n1pl1ipocla witl1 t1·ac·es of ,,,ate1· n1ites, Corixas 
and moll11sl{:s ( tl1e last in ElllJomotis). Tl1e E11tomos­
t1·aca we1·e fo1·t)r-t,,To IJCl" cent. Cladoce1·a, 11inetee11 11e1" 
cent .. Cope1)ocla a11d 11i11e pe1· ce11t. Ost1·acocla. 

A ..:i11g·le I-Iaploido11ot11s a11 incl1 a11cl a11 eig'l1tl1 in 
l engt11 , l1acl ea ten Cl1i1·ono1nl1s la1"vre ( seve11 t}T-fi,re 11e1" 
cent.) a11cl la1·,Tre of Prtli11ge12il1 bil·ii1Pctfa . 

EsocIDJE. · 
I dicl 11ot l1a,.,e tl1e g'oocl f 01·tl111c to o l)tai11 an)'.,. young· of 

tl1e commo11 pike, ancl ca11 only 1"epo1"t 011 tl1e food of a 
single Esox sal111,0 1ieiis a11 i11ch ancl a fol11·tl1 in le11gtl1. 
This speci111en, take11 at P ekin, Ill., on tl1e 2c1 of J u110, 

l1ad al1·eacl3r beg·l1n its life labo1· of tl1e eli111ination of 
little 'fishes, tl1ese n1aki11g· abo1.,1t t,vo-fiftl1s of its food. 
The re111ainde1" consistecl of C1"ustacea, co111posed al)out 
equally of }¥Ol111g· Ampl1ipocla, Dapl111iidre a11cl JJyncei.da:. 
ThP p1·ese11ce of so la1·g·e a c111a11tity of t.lJese minute En­
tomost1·aca i11 tl1e sto1nacl1 of a picker·el of this size, is 
sufficie11t ev"icle11ce tl1at tl1ey fo1--m tl1e p1"incipal ·pa·r·t of 
itB foocl at an earlier age. 

• 

• 



, 

• 

74 On tlie Food of Yoit1ig Fislies. 

CLUP EIDJE . 

vVe come nrxt to twel,Te specimc11s of t]1c _gizzct ,·rl-.-; /1(1,cl 
(Dorysoma), v\:l1ose minl1te f1·y s,, .. arm i11 co1111tless 11u111-
·bers in tl1e ,,,.ate1·s of ot11· la1·g·e1· 1"i ve1·s in 111itl :l11111ne1·. 
These '\\Tel"e tal{en i11 J llne a11cl ,J llly, f1·0111 tl1e Illi11ois R., 
f1"om Ottawa to Peo1·ia. Tl1e sn1a.llest of tl1 e g·1·0111) ,,Te1·c 
twenty mm. long l)y two 1nm. ,vide-as slencle1· as C)Tl)1' i-

11oids and 11ea1·l}.,. C)'li11d1 .. ical, altl1ol1g·l1 the acll1lt is a l1ig·l1, 
tl1i11 :fisl1. I was g·1·eatly i11te1·estecl by tl1e clisco,'"e1·!.,. tl1at 
the maxilla1"ies of these smallest speci111e11s a1 .. e 1)1·0,Ticlecl 
with teeth-a si11g·le 1"0,,r of 11i11e 01· te11 011 tl1e lo,,Te1· ec.l~;e 
-although tl1e 1nol1tl1 of tl1e ad11lt is e11tirel~,. tootl1less 
ancl smooth. The inte1"11al st1"l1Ctl11"e also cliffe1·s 1·c11-1a1·l{­
a.bly from tl1at of tl1e acl11lt, cspecia1l)T i11 tl1e 11111 cl1 g·1·e,1t­
e1· simplicity of tl1e digesti,re appa1·atl1s. In a )T<-11111g· g·iz­
zard-shacl se, .. e11-te11ths of a11i11cl11011g' b3r 011c-te11tl1 J1ig·lJ, 
the intesti11e ,,ras f ol1ncl to pass £1·0111 tl1e a11te1·io1-- e11cl of · 
the stomacl1 to tl1e ,re11t ,,Titl1 011],r 011e sl101't f 01·,,,. t11·(l tl11·n 

• 

of abo11t a fo11r·tl1 t.l1e le11g·tl1 of t l1e l)ocl>.,. ca,rit~r, 111atlc a 
little ,vay be]1incl tl1e sto111acl1. rtlil1ol1g·l1 tl1e 11111 cc)11~ ~111·­

face of the i11testi11e was at tl1is time , ,.el')r 1·ugose, t,}10,,T_ 
ing a com111e11ci11g· complicatio11 of tl1e cligesti,,.e s~-ste111, 
there was 110 t1·ace of })yloric cmca. Tl1e i11testi11c ,,-tlS 

fillecl witl1 C}Tp1·i s, Cl1)rclo1~l1s, Alo11a, (; ).,.clo1)s, etr. 
On tl1e ot l1e1· l1 a11cl, i11 a fis 11 t]11·ee a11cl tl1 r ee-f (,111·t.l1 ~ 

inches lo11g·, s]10,,-ing· tl1e g·c11e1·al cl1c11·c1(•t01·~ of tl1 e c1<l11lt, 
the in tes ti11e passecl l11 )"\\"a1·cl anc1 l)ac1{,\'a 1·c1 t·1·<,111 it~ 
origin, r·111111ing· \V"itl1ol1t flcx111·c.\ tl1e ,,-l1olc lc11g·t 11 <>i~ tl1<\ 
body cavit)r ( tl1is pa1·t bej11g' ro, .. e1·c(l witl1 <:111 i111111 c\11He 
1111mbe1" of p)·lo1·ic cC£ca), t]1e11 tl11·110cl f()l'\\"tll'<l ti, tJ1c.\ 
stomacl1, 1·a11 l>acl{ £1 .. 0111 tl1e1~e abo11t 011e-tl1i1·<1 <>f' tl10 ,vil.\T 

to th C ve11 t, tl1 e11 t111·ne(l f 01'\\rcl l'(l a11(l )'}lll a t.o l'lllOllR 

rou1·se benea tl1 tl1e ston1 ac·lL to t.11 e 1)c1·i ra l'< li (1 l 111 e r11 l)t'tt110 
and bacl{ ag·ni11, also to1·tl1011sl)r, t,,To-t]1i1·cls of t.l1c ,,-,1) .. 'le) 
t.he vent. Fr·o111 tl1iH point it 1·c111 foJ'Wftl'(l ,1g·c1i11 ti) tl1c\ 
stomach, a11cl C'l "Ossj11 g to t l 1 c left side~, 1·c111 1·01)et1 t<.'<11 :T 
backwarcl a11d f or·v,Ta 1·<1 111 t 110 1>oste1·j OI' pa 1·t. of t 11 0 llo<l )'~ 
cavity, m::-1l{i11g· Re,r011 t111·11s bet,,1 ce11 tll(' Rt.()lllcl.Cl l clll(l , .. ('lit 

l>efor·e ope11i11g, tl1t1s exte11cli11µ;, i11 ,1.ll, ,1,l1011i. c\ig·l1t ti1r1<.\ :~ 
tl1e lengtl1 of tl1c~ ])(11·i,ris(1Cl'cll rr1,·it) ... rr11i s i11tc\Ht illl 1 \\' it;-: 



• 

• 

0-Ji tlie Food of Y oii1ig llishes. 75 

,vell filled "'ritl1 mucl ,,1itl1 0111.)r a sligl1t sp1·i11]{]jng· <)f l1ni-­
cellula1" .1\lgre. 

M uc.h as these you11g resemble you11g Cyp1·i11idre, they 
crtn be easil}r disting·uisl1ed from tl1em by the very long 
rtnal fin; a11d £1·0111 tlJe l1rook sil,rersides (Labidestl1es), 
to which tl1ey bear s0111e· st1pe1--ficial 1"ese1nblance, by the 
absence of a spi11ous do1·sal. 

These t,vel,re fishes, all unde1· t ·\\TO i11cl1es i11 le11g·th, had 
eaten about ninet")T p er· cent. of E11tomost1"aca, t,;vo pe1-­
c·ent. of Cl1i1·onon1t1s la1--, rre, ancl f 01" the 1·en1ai11cle1·, Algre. 
The Crustacea ,ver e abol1t eql1all)- Clacloc2ra an<1 Cope1)­
oda. Among the former were Dap,li1i1ict 1Jitle.1', Sit1io­
ceplia,li1s a.11ie·ricaii·its·, Ceriodapli,nict, cle1itatci, Bos11u11a, 
Chydo1·us and Alona. In a specime11 tl1ree-ql1arte1·s of an 
inch long wl1icl1 I toolc fro111 tl1e stomach of a ll101·one 
i1iter·rupta, I found a fevv sp ecimen s of L eptoclo1·ci liyct­
lina ( 1) Lillj. Tl1e Copepocla ,,Te1"c a]] C~'"clops, so f a 1· a .· 
recognizable. · 

0YPRI N ID1E. 

A sing·le n1i11ute 111in11ow, tl11"ee-eighths of a11 i11cl1 lo11g·, 
which I could 11ot cletermine specifically, had eate11 Dapl1-
11ids ( twenty-five per c·e11t.) and Cl1ironoml1s la1·vTre .. 

The specime11s of the com111on cliub 1ninr;ioiv (Se 1,io til·its 
corpo1,.alis ), 1·angi11g f1"om five- eigl1ths i11ch to 011e incl1, 
i11dicate somev,rhat doubtfully a11 exception to the g'e11eral 
1~u1e respecting the ear·ly food of fishes. Only seve11 1)e1-­
cent. of tl1ei1'" food was Entomostraca, ana tl1e ,vl1ole re­
mainde1'" consisted of filan1entol1s Algre. It shot1ld l)e 
noted, ho,vever, that twe11ty per cent. of tl1e foocl of tl1e 
smallest specin1en, ,,rhich was five-eigl1ths of a11 i11cl1 
long, was Cyclops, and it may be that Semotilus lives 
vvholly on Enton1ostraca at first, merely cha11ging its 
l1abit earlier tha11 most of its allies. 

Two specimens of N otropis, an incl1 ancl a l1alf 111 

lengtµ had eate11 11othing but D·apl1nids. 

0ATOSTOMID1E. 

Thirty specimens, 1"epresenting five ge11e1"a of tl1is pe­
culiar family, were studied. A very curious feature of tl1c 
food of the young is the frequ ~11t dependence of sl1cke1·8 

• 

• 



76 On tJie Food of Young Fishes. 

of co11siderable size-six incl1es long or more-upon 
food mo1"e t1·i ,.,ial than Copepoda 01" Lynceidre; viz., upon 
1--otife1"s, Protozoa a11d 11nicellular Algre. While only such 
P1"otozoa we1"e f ot1nd as a1·e furnished witl1 firm tests 01· 
carapaces, 3Tet tl1e abundance of Diffiugia and Arcella in 
the i11testines of these fishes leaves little doubt that the 
1no1"e pe1--islJable PI·otozoa 111ust also be taken in consider­
alJle quantit),. It is a11 inte1"esting fact that even here the 
smallest s1)ecime11s we1·e f ot1nd feeding on Entomostraca 
011ly, a11cl it is tl1erefo1--e possible tl1at tl1ese form the first 
food of the fa111ily. 

Te11 s1Jecin1ens of tl1e sto1ie-1·olle1· (Hype,12teliit11i nigri­
cci1is), rangi11g f 1·0111 011e and tl11"ee-eighths to three inches 
1"ep1"ese11t t,vo dates a11d localities. The four smallest, 
11011e la1--g·er tl1a11 ar1 incl1 a11d tl1ree-f ourths, were taken 
f1·on1 tl1e lo,,,.e1· Fox, J11ly 9, 1879. Tl1e otl1ers were ob­
tai11ecl f1"01n J\tiacl(ina,,T C1·., in ~T oodf orcl Co., Ill., in the 
latte1· pa1·t of .,._~11g11st. Tl1e situatio11s ,vere similar, both 
st1"eams bei11g· Rwift a11cl 1"ocky wl1ere these fishes ,vere 
caug·ht. Tl1ei1" foocl ,vas cl1iefly tl1e larvre of Chi1"onomus 
(ni11et3T 1Je1" ce11t.), tl1e 1"e111aining· te11tl1 l1ei11g p1"n1cipally 
1nade up of Alona ( six pe1" ce11 t.). Ost1"acoda, Copepoda, 
a11d Alg·a: eacl1111aclc abo11t 011e pe1" cent. of tl1e food. The 
. .-\lg·re ,ve1"e 111ostl)T c1iato111s a11d clesmids, Closteriu1n being 
especiall37 co1nmon. l\{a11~,,. Diffil1gia a.nd Arcella ,vere 
also f ot1nd i11 tl1ese fisl1es. 

vVe t1"ace i11 tl1is a 1·e111a1·l{able l"esemblance to t l1e food 
of tbe da1"te1"s, ,vl1icl1, it ,vill be 1·emembe1·cd, frequent 
simila1· sitt1atio11s. LE1rki11g tl1e suclti11g mol1tl1 of Hypen­
teliu111, tl1ey do 11ot tal<e P1"otozoa 01~ 111'1icelll1lar Alg~, 
l1ut in othe1-- particula1"s ag'1"ee closely ,,ri tl1 this species. 
Tl1is cu1"ious fis]1 is pec11liar a111ong· the sucko1·s in t]1e un-
11s11al developn1e11t of t]1e 1Jecto1"al :fins-a (1isting·uishing· 
f eatt11~e of tl1e cla1"te1·g ] ike,;vise-do11btlesR 1·elatod, i11 
l1otl1 cases, to t]1e co11sta11t st1·11gg·le with cl s,,ri·ft c11rr0nt. 
"\~Te 111ay also 1·0111arlc tl10 cla1·te1·-lilce g·low of color· ir1 tl1<• 
),.ou11g· of tl1is ~})ecies-~1 vu1·y })ec11lifi1· clisti11ctio11 ,1n1<)11g· 
t.11e Catosto111 i<1m. T1Jis is 011e among· ma11)r f'c1c.t8 whicl1 
i11dicat(1 tl1at 0x1)osu1·c to ligl1t has g·1·eat p1·i1nc1.1·y effect 

. (>TI tl1e rolo1· of -6Rl10R-a11 effrc··i <)ftc11 s11p111·r8Rrrl. 



Oti tlie Food of Y 01,tt1,g Fis lies. 77 

th1·ougl1 natu1--al selection, by seco11dary influences, bl1t 
manif esti11g itself ,vhere tl1ese are 11ot b1"011ght into pla}r. 

This species is in marlred cont-1·ast witl1 the darte1"s, 
not only in the rapidity of its g·1·0,vth and the ultimate 
size attained, but u1 the form a11cl size of tl1e heacl, wbiclJ 
in tl1e c1arte1·s is small and pointed, bl1t i11 tl1ese fishes is 
t1nusually la1"ge, square and st1"011g. 

The principle of adaptation l1as l1ere 1·esulted in a dif­
ferent line of develop111ent. ,Vhile the little Etheostomat­
idre have become fitted to slip ancl pr3r abo11t beneatl1 tl1e 
stones for tl1ei1" food, Hype11teli11m has acql1i1·ed tl1e 
power of l"Olling the stones bef 01--e it. As it g1--o,\Ts large1·, 
it resorts, of course, to deeper ,,rate1·, bl1t a lways p1"efers 
the rocky r eacl1es of the stream. The mo11ldi11g power of 
11atu1·al selection could scarcely have a l1ette1-- illl1stration 
than that affor·ded by the adaptive char acte1·s, both simi­
lar a11d dissimila1·, of these two ,,ridel3r separated grou1)s 
of fish eR. 

A single specime11 of black sitcke1· (lJ!l i-1iyt1·e,rict 11iela .. 1z­

ops ) was too large p1·ope1·ly to co1ne ,vitl1i11 this g1·0111); 
but, althoug·l1 six i11ches long·, 111ost of its food ,vas 0)"­

clops ( eig·l1ty pe1-- cent.). Other items vvere ... t\_l(Jna, Dif­
fil1gia, Closter·ium and very }roung U11ios. 

Four cliitb-sitcke1·s ( E ri1YJiyzo1i s1rcetta), t,,To of vvhicl 1 

were tl1ree-fourths of an incl1, a11d two an incl1 and n 
quar--te1" long·, differe(l g1"eatly in foocl fro111 tl1e fo1·egoing. 
The two s111alle1· speci111ens, f1·om Long· L ., near Pekin~ 
talren June 2, 1880, l1ad eaten 011ly Cladocera, with a trace 
of water 1nites. Cl1ydorus ,,ras tl1e p1"incipal element of 
their foocl ( eighty per cent.) , lJllt Plel11·oxl1s, Alo11a an(1 
Scapholeber·is 1,iitc1·0,nata v\7ere also p1 .. esent. In the tvvo 
larger specimens, locality a11cl date l1nkno,v11, a surpris­
ing numl)el" a11d ,.,ariety of the 1ni11utest animal a11d veg­
etable f 01·m·s vve1·e f ot1ncl. Squa111ella, _1-\_nu1 .. rea of several 
species., Rotife,· v1tlga1·is ancl otl1e1· Rotifera; Diffil1gia 
and Arcella * amo11g· tl1e Protozoa; Ch1·oococc11s, Closte-

* Slides of the food of this genus and Myxostoma were submit tecl to Dr. 
Jos. L eidy, of Philadelphia , and Prof. W. S. Barnard, of Cornell Univer­
s ity, N. Y ., and these g·entlemen kindly sent me the f ollowing na;rnes of 
Rhizopoda as occurrin g therein: From Prof. B arn arcl , D i,ffl:u,gia c1,cu1ni-
1iata, pyrifo1·11iis, co1istricta a nd globosa _; f rom Dr. Leidy , D. pyriforrrtis. 
acuminata~ globiilosc1, lobost o111ci a n d Arcellci vit lgaris and d iscoides 



78 011i tlie Food ·of Young Fishes. 

1·ium, Cos1nar·iun1, Sta11rastrun1 and various diaton1s 
a1nong the Algre, were the principal genera. A minute 
Agrion la1--,rre, a ve1"y young Amphipod, ancl larval Co­
l)epoda (nauplii), vvere the only otl1er ki11ds recognized. 
It ~ras obviously impossible to make any estimate of the 
1·atios of sucl1 mint1te a11cl va1"ied objec·ts occur1·ing' ill 
sl1ch g1·eat quantit;r, ancl I have contented myself ,vitl1 c1 

simple enumera.tio11. 
A specimen three inches 1011g, £1--0111 Peo1"ia Lake, in 

Octobe1 .. , l1ad eaten only Oopepoda ( Cantl1ocamptus) 
,,ri th a trace of Chironoml1s lar,rre. 

Ten specimens of 1red-lio1·se (Myxostoma), varyi11g' i11 
length fro111 an i11cl1 to t,vo and tJ11'ee-fol1rtl1s, take11 i11 
J l1ly ancl Al1gust, f1·on1 tl1e Fox and Illi11ois rivers a11cl 
-f1"01n Macki11a,, ... Cr·., s110,,T no impo1"tant differences of 
food. 

I11 tlie s1nalle1" speci111e11s, ta.l{e11 f 1·0111 tl1e Fox and Illi­
nois, E11to1nost1--aca, especially Cyp1 .. ids , ,, ... e1·e 1·clativel)T 
more important, sometimes constituti11g 11ea1·l3r the wl1ole 
ioocl; bl1t no attempt was 1nade to fix precise 1·atios. I11 

tl1e fo11r· la1·ge1" specime11s f1·om W ooc1fo1·d Co., tests of 
Diffiugia were esti111atecl to £01,111 eig·l1t3r-:fi, ... e pe1· ce11t. of 
tl1e contents of tl1e i11testines. Tl1ese specime11s were 
taken one at a ti111e, sev ... eral miles a 11a1·t, along a 1"ock3" 
})art of the stream. Besides the species of Difflt1gia and 
1-1.rcella gi ve11 i11 tl1e foot 11ote, va1·iol1s clesmicls and dia-• 
ton1s ,,:re1"e abundant, ,,1ith filament<)l1S Algro, rotife1 .. s 
( Squa111ella ancl Rotif cJ· -v l,l•lgar;·is), Cyclops, Alo11a, Ple11-
1·ox11s ancl water mites, Chi1"011om11s and otl1e1· Dipterc1 
la1·,r~1?, some i11clete1·minable veg·etal)lc 1natte1· a11cl a si11g·le 
Tl11·i1)s ( .Hemipte1·a). The srnall pe1--ce11tage oi Cl1i1·011-
0111t1s la1·vre sho,,rs that tl1is Rpecics l1as not t,l1e l1abit of 
tl1c stone-rollc1·. 

Tvvo specime11s of tl1c coJ,i1,1io1i ~i;i,cke,1· ( Castost<J1111, .1.,• 
co11i11ie1~son,ii), six inches and six a11d th1·ce-fo111·tl1s i11 

• 

lcngtl1, tal{en f1·0111 Marki11,1w C1·., i11 _t\ 11gt1st c111<l ,1 t111t\, 

l1ad ea ten f oo<.1 so sin1ila1" to tl1at or tl1c l)l'C<·rcl i11p; g·<~11 t1:-; 

tl1at detailed clesc1·iption is ·11nneccssary. 
Two specime11s of tl1e commonest l)1iff'alo-fisli (I clitliyo­

b1,ts), seven-eigl1tl1s of n11 inch lo11g·, l1,1cl <.'ate11 111<)st f1~cel)' 



79 

ol' 1111icelll1la1-- l ~lgrc (sixtJr-tli1·ee pe1· cent.), of vvl1ich onl~r 
P1·ot()Cocc11s a11d Closte1"il1111 were 1·ecognizec.1. SpecimenR 
<)f A11l11·~;;1, ,,Te1·e 1·ecl{o11ed at twe11t3r-se,,en per cent., ancl 
the 1·emaincler of tl1e f oocl co11sistecl of Copepoda and 
Cladoce1·a. Tl1ese specin1e11s ,,,e1·e tal{en from the Illinoi s 
R ., i11 ea1·l1r J 1111e. 

Fo11r cctr·p-sitcke1~s ( Ca1·pio<les), se,re11-eig·l1ths incl1 to 
t,\ro incl1es long, tal{en f 1·0111 tl1e Illinois and £1--om Clear· 
L., i11 I{ent11cl{y, l1ad fed lil{e tl1e p1 .. eceding gen11s, except 
tl1at the Enton1ostraca ,,Te1"e i11 large1" q11antity (forty­
eigl1t pe1· cent.), a11d i11cl11c1ec1 a n11m·be1" of Ostracoda, 
,,7 l1ile tl1e 1"otif e1"s ,,re1--e co111pa1"8., ti vely f e,,T. Tl1e Da p11-
11iidre of tl1e Illinois R. specime11s we1"e 11ea1"lJ.,. all Sca-pli­
nl ebe,ris 111itc1·onatct. Cantbocarnptl1B i11 t1"i·\,.ial n11m l)Cl"R 
was also f 011ncl in a single s1Jeci111e11. 

Reviewing· the f oocl of tl1ese tl1i1"t).,. Jro11ng· suckers_, ,ve 
see tl1at tl1e,r cliffe1" f1·om tl1e otl1er fa111ilies studied in the 

• 

large1· foocl-1·eso111·ces ope11 to tl1e111; fo1", ,vhile the st1"t1c-
tu1·e of tl1ei1-- moutl1s cloes 11ot l)l"O]Jil)it t]1eir tal{ing· E11to­
:rnost1·aca, it e11ables tl1en1 to c11 .. c1w 11pon the 111ultitl1des of 
111i1111te 01·g·a11isms fo11ncl 1111011 t]ie l)otto111. Eviclentl},. 
tl1ey l1a,"e 110 mea11s of selecti11g s11c11 micr·oscopic st1·t1c­
tu1·es f1·om tl1e n111d i11 ,,r}1ic 11 tlJ ese 1110s t f reql1entl)' 1·0st, 
ancl consiclerable quantities of clirt a1·e co11seq.t1entl1r 

•• 

ofte11 fo1111cl i11 tl1e i11testi11es; l)11t fro111 tl1e '' 1·icl111ess '' of 
tl1e co11te11ts I infe1· tlJat tl1e3r r1011l)tless l1a,"e tl1e J)o,,1e1 .. 
of disti11g'l1isl1ii1g m1.,1cl containing· a larg·e pe1"centage of 
OI"~a11ic 111atte1" f1"om I"elati,rely ba1·1·e11 po1·tio11s. 

• 

SILURID.lE. 

N11111c1·011s SJ)eci111e11s of the 3,01111g of tl1is famil)" sl10,,r 
tliat, 11otwjtl1sta11cli11g· its 111a11),. pec11lia1·itios of str11ct111·e 
a11d habit, it is no exceptio11 to tl1e ge11e1·al rule 1"espect­
ing t.11e f oocl of tl1e 3ro1111g. Tl1e .·n1allest of tl1ese s1)eci-
111e11s ,, ... 01 .. e f1"om a little school of minute f1"y, taken i11 
J 11ne f1·0111 t]1e f1"iendly p1 .. otectio11 of an olcl oyste1"-ca11 in 
tl1e Illinois R. Tl1ese little c1 .. eatures were colorless a11cl 
Bee111i11g·ly aln1ost l1elpless, and only th1·ee-eigl1tJ1s of a11 
jncl1 i11 leng·tl1. They l1acl al1--eady begun to eat, howeve1", 
anfl tl1eir sto1nac]1s ,,re1"e ,,--ell. fill ed ,,rith Cyclops and a 

• 



.. 

• 

80 01,i tlie•Food of Yo,lttig Fishes. 

few D·aphnids and Chiro11om11s lar,rre. These ,v~c1"e ce1·­
tainly Amiurus, b11t it ,vas of cou1"se i1npossil)le to tell 
the species. 

Other specimens of t]1is g·en11s, 111aking· tl1i1'tee11 i11 all, 
none longer than an i11cl1 a11cl fi,~e-eig·11tl1s, ,,Tel"C obtainec1 
fro1n va1"io11s places on the Illi11ois, ancl £1 .. om mucl.-l1oles 
i11 the ~1ississi1Jpi b,ottoms, i11 U11io11 Co. These tl1i1--tee11 
individuals were feeding al111ost wholl}r 011 Ento111ostracc1 
and la1"vre of Cl1ironomus, tbe latte1-- composi11g· sevent}"­
f our per cent. a11d the former eig·hteen pe1" cent. of thei1· 
food. Twenty-two per ce11t. of Cladoce1"a i11clt1de SimrJ­
cep,lialus a1ne1·ican1,is a11dS. vetitli£.s, C'eriodapl111ia a11d Mc,­
c.,,·otlirix latico1~1iis, * Ju1"., a species not l1ithe1"to 1"eportecl 
f1"on1 this cot1ntry. Amo11g· tl1e Lynceidre ( ten pe1" cent.) 
I recognized Ol1ydorus, Pleit1·oxiis dentatiis, Alona ancl 
Eitr.ycercus lct11iellatus, and amo11g tl1e Ostracoda a spe­
cies of Candona answeri11g· p1 .. ecisely to the clescription of 
Candona bifctsciata, Sa}'". A few you11g· Amphipoda and 
ct f evv unl{no,vn i11sects' eg·gs acco11nt f 01· tl1e 1"e111ai11de1· 
of the food. 

Six speci111ens of Not i t 1 ·zf.s s icili,s, , r;:11•)ri11g in le11gtl1 f 1·0111 
seve11-eigl1ths of an inch to a11 inch a11d a ql1a1 .. te1", dif­
fered fron1 the foregoing· in the mt1cl1 larger pro1Jo1"tio11 
of Chironomus lar,rre (fo1·t3.,.-011e pe1· ce11t.) clncl i11 tlJe 
t,venty-six per cent. of )"Ot111g· Allorchestes cletz.fata­
eaten by the la1'ge1" speci1nens. Tl1ese l1ad t1lso take11 
f:ieven per cent. lar--vm of EpJ1eme1"idre. T11ose 11nder a11 
i11ch in lengtl1 were pect1lill1· 0·11l)r i11 tl1e la1·g·e 1·atio of 
( :hironom11s ]a1•,Tre ( sixt)r_:fi,Te 1)e1· ce11t.), a fact p1"ol1abl)~ 
i11dicating tl1at tl1is s1)ecies scclts its f oo<l cl1i efl>" .011 tl1c 
1n11ddy bottoms. 

No speci1ncns of tl1c ot11c1· g·ene1·ft of catfis11es ,,·e1·e 
talrcn small e11011g·]1 to s11ow tl1oi1· ca1·licst foo<.l, bt1t Ho f c11· 

as ca11 be j11clg·c(l f1·om tl1e food of f Ol11· spccimer1s <) l' 
Ictalu1·us, £1·0111 two ancl a J1alf to tl11·ec ct11(1 a ]1alf i11cl1c~ 
1011:~, tbe otl1cr gene1"a ,,rill 11ot l)c fol111cl to cliffr1· cR11<"\ri,ll­
ly i'rom the f oreg·oing·. 

* Possibly this is not th e species c:ilecl. bt1l n <·nrrful <'()1111>.1ris1ln ,vitl1 
the description a n cl flg·ure~ i11 Lilljeborg·'~ "Cru:--tnc·t.>:1 e'\ ()1·11 inil>ll~ rcrril>t1s. ·· 
etc., failecl to show any cl ifferen ce . 

• • 



• 01i tlie Food of Yoit1ig Fislies. 81 

AMIIDJE. 

A si11g·le dog-fish (A111ia) , one a11d three-fourth s i11ches 
1011g, taken in June, l1ad eaten seventy p e1" cent. of Ento­
most1--aca- about equally Copep oda and Cladocera-a11cl 
t\\ro per cent. of larv ro and pupm of Chirono1nl18. _,_f\. f c,,r 
}TOl1ng Allorch estes ancl som e Corixa s co1nplet e tl1e l)1·ief 
list. . 

. 

Se\1e1·al specimen s of A 111ia t111de1" 011e incl1 in le11gtl1, 
,,rl1ose anatomy I stu cliecl three years ag o, I r eme1nl)e1 .. to 
l1ave l1ad tl1eir intesti11es pack ed ~ritl1 Ento111ost1~aca. 

L E PI DOSTEIDJE . 

Here also I shall have t o co11te11t myself wit l1 such 
hints of the food of the y oung as are given by t,vo or 
three specimens, as the y ol1ngest a r e 11ot yet comn1011 
enough in our collectio11s to sl1p1)ly rno1 .. e 111a te1"ia l £01-- a 
stt1dy of thei1" f ood. One of tl1e two smallest ga1·s exam­
i11ed, an inch ancl a fou1--tl1 in le11gtlJ, taken i11 J l111e, n ea1'" 
Peo1--ia, l1ad fillecl itself witl1 i9rctpliolebeJ·is 11i2tc1·0,icttcc, 
and the other hacl talren 011ly a 111inute fish. .1\. speci111en 
two incl1es long and only a11 eig·l1th of a11 i11cl1 i11 clerJtl1, 
1·u1·11ished a strilr.ing illust1"at io11 of t l1e , ro1"acit~~ of this 
t error of our streams, a s its sto111acl1 cont ainecl sixteen 
111inl1te Cyprinoids . 

1-S'f 7£ 111,171,a.r·y . 

A sufficient r ecar)itula t ion of t l1c f <)1·0going c1ata i s af­
fo1·decl by tl1e appen cl ec1 t able of th e f oofl of t11e cliffe1"e11t 
genera. It may be vvo1 .. t l1 ,,rhile to say tl1at all tl1e materi al 
11pon which the foregoing statem ents 1--est, as ,vell as all 
tl1at used i11 the p1 .. ececling paper, has b ee11 ca1--efully p1"e­
Re1 .. ved, and 1na3r l)e seen at any time by tl1ose in t e1"ested , 
at the State La~o1 .. atory of Natural Hist ory . 

The gener·al co11cll1sion from these o bser,ra tion s is tl1e 
s11preme impo1·ta11ce of Entomostraca and tl1 e 1n inl1te 
aql1atic larvre of Dipte1"a as foocl f 01-- 11ea1 .. ly or CJ11ite all 
of our f1"esh-,vater fishes-a conclusion that g i \res t l1ese 
trivial and neglected creatl1res, of whose very exist e11ce 
tl1e majori·ty of tho people are scarcely aware, it p1 .. 0111i­
nent place among tl1e most val11able anima.ls of tbe State, 

-



• • 

82 

for \\7itl1out them all 01,11· vvater·s '"roulcl be ,ri1"t11ally depop­
ulated. Otl1er· facts of eminent interest thus brought to 
vie,v ai·e tl1e magnit1,1de and inte11sity of the competition 
for food an1ong the young of all 01 .. ders of fishes, where a 
st1--eam is fully stocked, and the injurious cl1a1"acter of 
s1,1ch a s1Jecies as tl1e sl1ov:el-fisl1, whicl1 feeds 011 E11to­
most1·aca th1·ol1g·l101,1t its life. It is p1·obable tl1at all :fisl1eR 
,,rhicl1 a1·e not especially adaptecl to tl1e food 1"equire-
111ents of tl1e n1ore valuable fishes, are h111·tful to them, be­
cal1se tl1ey limit the food available for the yol111g. The 
Sl1n:fisl1es, ,,Those shape protects the111 from many ene­
mies, ancl tl1e catfishes, ,,;-•itl1 their ar1no1" of poisonecl 
S})ines, a1--e instances in point. Wl1ile thei1" young compete 
,,1itl1 tl1e young· bass anc1 wall-eyed pike fo1" food, tl1ey do 
not .f11r11isl1 tl1e latte1,. any important food 1"eso11rce i11 
late1· 3rea1--s. On the otbe1" l1and, s11cl1 species as tl1e l1e1". 
bi , ... 01·011s 111innows and tl1e cylincl 1·ical s11c l{e1"s, v,rhic 11 dc­
})end llpon Entomostraca to a less exte11t ,vhen yo11ng, 01· 
take llp otl1er food at a 1·elativel:;r early pe1·iod, a1·e tl1ose 
'\\'"l1icl1 see111 to pI"omise best as food for tl1e l1igl1e1" fishe8. 

It is a curious coro.lla1·y f1 .. om tl1e above 1"easoning that 
a l)l"olific species l1aving· a11 abundant foocl Sl1pply, and it­
·self tl1e most important food of predaceo11s fishes, may, 
l))T e:~t1"aordinary multiplication, so dimi11ish tl1e food of 
tl1e yol1ng· of the latter as to cal1se, th1"011gh its 01,rn abun­
da11ce, a se1·iol1s dimi11ution of tl1e 11l1mbers of tl1e ve1")T 
species whicl1 p1"ey upo11 it. To pl1t tl1is statement intc> 
more conc1"ete fo1·m, it is not ce1·tai11 tl1at the excessive i11-

c1·ease of tl1e ~;izzarcl-sl1a<l, for instance, 1vo11ld l)e a bcnr­
fi t to tb e bla.cl< bass a.ncl })ilre-pe1·cl1 ,,1 l1icl1 f eec1 RO la1·gel)T 
l1pon it. In fact, it is clear that tl1c g1--eat o,Te1·stocl{ing of 
a strca1n witl1 g·izza1·d-sl1ad wol1lcl, by eve11t11ally r·educi11f{ 
tl10 s11pply of Entomostraca, ca11s0 a co1·1·osponding 1·c­
cluct ion in tl10 numbers of all the species of that st1·ea111 
h3r Rta1:vation of the yo11ng·; and tl1is clcci111atio11, appl)r­
ing t.o all i11 tl1e same r,ltio, wol1ld ti1l(0 cf~fcct 11pon tl10 
r;1 4 rlinri,·y num be1· of tl1 o <>tl101· species, 1)11 t 111)011 tl1 o ei·t 1·(1 -

0 rclinary n1t111 be1" of t]1e gizza1"d-shacl- ,,,011 ld 1·e<ll1ce tl10 
other spoci<!S l)e 1 ()"\i\7 th c 118l1al limit, l> t1 t 111ig·l1 t rto t evo11 
cl1t off tl1e <~xce.c;,c.; of tl10 Hl1afl al><),'O t,l1}1t lin1it. C<)llR<.'-



• 

que11tl)-, i111po1·tant as is the s11pply of food fishes for the 
p1--edaceous species, it is not less important that the pre­
da,c.eous species sl1011ld be supplied to eat up the food. 
He1 .. e, as else,vhe1--e, onlyr ha1"m can come from an impe1"­
fect bala11ce of the fo1--ces of 01·ga11ic 11at11re, ,vhether the 
exce s lJe u1Jo11 011e side 01" tl1e othe1". 

I11 tl1e effo1"t to i11crease tl1e "\7all1able fisl1es of a lal{e 01~ 
st1·eam, it is 11ot sufficie11t that the foocl of tl1ese species 
should be increased alone, l1ut at the san1e time special 
meas111·es m11st be taken to sec1,1re a co1 .. 1·es1)onding 111ulti­
l)licat.ion of the predaceous fisl1es tl1en1sel,res, otl1er,,7ise 
l)recisel}r the r e,rer se resl1lt 1na3r be 111·oc111cec1 fr0n1 tl1at 
i11te11dec1 . 

.t\s a further ill11st1"ation of so1ne of tl1e p1"actical bea1"­
j11gs of t l1e8e facts. it may be 11oticed that the free access 
of fishes to the ponds, lakes ancl ma1·shes co1111ec·ted witl1 
a s1·eam is a 111atte1" of the l1ighest importance. Running· 
wate1· is 1--elati,Tel3,. c1estit11te of Entomostraca, and hence 
fishes cle11ied access ".,.l1ile b1"eeding to slo,v or stagnant 
,,-ater i11 wl1ich E11tomostraca abo1111c1, have 110 chance to 
111ultiply. The conditio11 of fish life in the lower Fox R. 
,,~ill illust1·ate tl1is l)Oi11t. Tl1is strean1 takes its rise in the 
11l1111erot1s lakes of 1101--tb,,7 este1·n Illinois and southern 
,,Tisconsin, but in its lowe1· colll"Se l1as f e,v branches anrl 
110 stagna11t ,,.,.ate1·s c11·ai11i11g into it. Its o,v11 current is 
S,\~ift a11d mucl1 of its 1Jec1 is 1"oclr-:57

, ,,rl1ile the vast expanse 
of wate1-- of ,,7J1icl1 it f 01"ms tl1e ot1tlet prevents any great 

· oscillatio11s of its le,.,.el ,,Tit11 the co11seql1ent flooding of 
itdjacent la11cls. This pa1·t of the st1"eam is therefore 
peculiarly t1n:fit for b1"eecli11g p11r1)oses, and we shol1ld ex­
r,ect few fish to n1aintain tl1emselves in it if denied access 
to tl1e imme11se a11d teeJning· lJI"eeding g1"ou11ds of the up­
per pa.rt of the rive1--. St1cl1 access is effectl1ally c11t off 
by seve1"al dams, unp1"oviclec1 ·\\·ith fisl1ways, ,,1l1ich have 
1)ee11 th1"0,,.,.11 across tl1e st1--ea111. .1:-\_ fish vvhich e11ters the 
river from above the1"efo1·e cannot get back to breed-a 
fact ,vliich must m1favo1--abl,.,. affect the number of fishes 

• 

in both ri·\r{!l" and lakes, and is appa1"ently one ca,use of 
a11 111111sl1al scarcit3.,. of ga111e fisl1es i11 that streRm. 



• 

• 

• 

• 

8-1 01i tlie Food of Y 01.ing Fislies. 

TABLE OF FOOD OF Youxo FISHES . 

• 

* UJ • 

Pd ~ 0.. ... UJ 
"O 0 ~ ·- s:: Pd ..0 C'lS • 

UJ 0 8 • 
• Ci,) 

'"O '"O ~ U} 
QJ ... ·- - ·-Q C'lS ♦- 0 s:: ·- C. • 0 ... 

C'lS 0 ... • UJ ·- 0 C - >< ;;,.... 1-, (,,) ... ... 0.. 8 
1-, ... 0 C 0 I-, p_,. -Q) Q) C'lS UJ 0 ;;,.... ".j 

A.. ~ u ::r:: ~ 0 
QJ z u Cf) 

- - · 
N umber of • specimens ..... 6 I 43 I I 12 I 3 2 

' ' -

Size in inches ..... . .......... I@ I }4( i~@ I_½ I}( ½@ Ys ¾ I¼ 
I¼ 2 I¾ @I 

KINDS OF F 00D. 
Ratios in which each element of food 

was found. 

. I. FISHES . ..... ♦ ••••• ••• •• • • • • 
Dorysoma ...•............•.. 

I l. MOLLUSKS •.•..••..... 
• • • • 

• • • • 

I I I. INSECTS... . . . . • . . . . . . . o8 
1. Diptera (larvre) ..... ...... 08 

Chironomus.. . . . . . . . . . . . . . 08 
Corethra ................. . • • • • 

50 ..•. . . . . 40 •••• 

50 
• • • • 

•••• 

• • • • 

• • • • 

• • • • 

•••• • • • • • • • • • ••• 

t .... 
28 100 

26 75 
26 75 

• • • • • • • • 

• • • • • ••• 

. . . . 02 

. . . . 02 

. . . . 02 

• • • • t 

• • • • • • • • 

• • • • • • • • 

• • • • • • • • 

75 · · · · 
75 
75 

• • • • 

• • • • 

• • • • • • • • 

• • • • 

• • • • 

• • • • 

. . . . 
• • • • 

• • • • 

2. Hemiptera (young) ....... . • • • • • • • • t .... •••• • ••• • • • • • • • • • • • • 

Corixa .... .. .. .......... .. . • • • • • • • • t .. . . . • • • • 

3. Neuroptera (larvre ) ....... . 
Ephemeridre ............. . 

Palingenia ............. . 
IV. HYDRACHNIDtE .. .... . 

• • • • 

• • • • 

• • • • 

• • • • 

V. CRUSTACEA............ 92 
Amphipoda (young) ........ . • • • • 

Entomostraca... . . . . . . . . . . . . 92 
Cladocera. . . . . . . . . . . . . . . . . 52 

Sididre . ................ . • • • • 

Da phniidre. . . . . . . . . . . . . . 50 
Lynceidre. . . . . . . . . . . . . . . 02 
Leptodoridre .... ....... . • • • • 

Ostracoda ....... . ........ . • • • • 

Copepoda. . . . . . . . . . . . . . . . . 40 
VI .. ALGIE ..............•. • • • • 

. . . . 02 

• • • • •••• 

• • • • • • • • 

2 5 .... 
25 
25 

• • • • 
• • • • 

• • • • t .... • • • • 

50 
• • • • 

50 
40 

• • • • 

• • • • 

• • • • 

72 
02 

70 
42 
02 

36 
04 

. . . . 6o 

. . . . 20 
• • • • 

• • • • 

• • • • 

40 
40 

• • • • 

. . . . 20 

. . . . 20 
. . .. . . . . . . . . . . . . . 
. . . . 09 • • • • 

IO . 19 .. . . . • ••• 

• • • • 

• • • • • • • • . . . . . . . . 
• • • • • • • • • • • • • • • • 

• • • • • • • • • • • • • • • • 

• • • • • • • • • • • • • • • • . 
• • • • • • • • • • • • • • • • 

90 25 07 100 

• • • • • • • • • • • • • • • 

• • • • 

100 
100 

• • • • • • • • • • • • • • • • 

34 2 5 .. .. JOO 
04 .... 
02 

t 
48 
08 

• • • • 

. . . . 
• • • • 

. . . . 

• • • • . . . .. 
• 

• • • • . . . . 
• • • • • • • • 

07 . ... 
93 

* For cl et ailed t a bles of th~ foocl of tl1e }'Ottng· of tl1is f a mily see t l1e 
1)r ececli11g· p a p e r on tl1e f ood of the Aca ntl1opteri. 

• 



' 

01i tlie Foocl of Yoiitig Fislies. 85 

TABLE OF Foon OF YOUNG FISHES-Continued. 

• 

• 

8 • (/) 
~ • ::, "' ::, • 8 

• ·- C ::, rn Q) - ..c Q.) • ..... Q.) 0 0 rn • ..... ..... 0 '"C ::, fll rn • N .. 0 ..,:.i C >. IJl >. 0 .... .., .... • '"C V 0 .!:l ·- ::, ~ < 
0. 8 X 0. . ::, ·-..... ·- ·- c.. f-4 .... 8 

..... 
8 >. ·- >, ~ 0 0 .... ~ Q) 

:r: w ~ u u ~ z ~ .....1 t-4 -. • 

Number of .specimens .... JO 4 IO 2 4 13 6 I 2 126 
--

Size in inches ........... 1¾ U@ I@ ¼ ¼@ ¾@ ¼@ •¾ 1_¼ 
@3 I _¼ 2¼' 2 1¾ I}.( 

Ratios in which eacl1 element of food 
. 

KINDS OF Fooo. was found. 

I. FISHES . ............ • • • • • • • • • • • • • • • • • • • • • • • . . . . • • • • 50 • • • 

I I. INSECTS . ......... 90 I I t • • • • • • • • 22 58 25 • •• • • • • . 
Eggs. . . . . . . . . . ....... • • • • 04 • • • • • • • • • • • • • • • • •••• • • • • • • • • •• 
1. Dtplera (larvre) . .. ... . 90 t 18 41 IO 

, 
• • • • • • • • • • • • •••• • • • 

Cbironomus ............ 90 • • • • t • • • • • • • • 16 41 JO •• • • • • • 
2. Co/eoj)tera (larvre) ' IO . -.. • • • • • • • • • • • • • • • • • • • • • • • • • • • • •••• • • • 

J. Hemzplera. • • • • • • • • • • t t t • • • • • • • • • • • • • • 15 • ••• • •• 
Corixa ... ... . . .... • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 15 • • • • • • • 

4. NeurqjJtera (larvre) . .. . t 07 • • • • • • • • • • •• • • 07 • • •• •••• • • • 
E\ bemeridre .......... t 04 • • • • • • • • • • • • • • • • 07 • • • • •••• ••• 

11 . HYDRACHNIDJE . , . t 03 t • • • • • • • • • • • • • • • • • • • • • • • • .... 
l V. CRUSTACEA . .. . .. . 09 51 t 10 48 78 40 75 so • • • 

Amph;poda (young) . . .. . . • • • • t • • • • • • • •• • • • 04 20 05 • • • • • • • 

Entomostraca ....... . .. . 09 50 t IO 48 74 15 70 50 • • • 

Cladocera ............. 07 49 t 05 23 22 o6 35 50 • • • 

Daphniidre .... . . .... 01 02 • • • • • • • • 23 I I • • • • 35 50 • • • 

Lynceidre ........ . .. 06 47 t . . . . • • • • IO o6 •••• , .... • • • 

Ostracoda .... .. .... . .. 0 1 01 t . . . . •5 12 • • • • • • • • • • • • • • • 

Copepoda ...... . ..... . 01 t t 05 I O 40 09 35 • • • • • • • 

V. ROTIFERA. • • • • • • • • • • . . . . t 27 t • • • • • • • • •••• • • • • • • • • • 

VI. PROTOZOA . .. ... t 15 t . . . . t • • • • • • • • • • • • • • • • • • • • • 
V I I. ALGJE ......... 01 20 t 63 52 • • • 02 • • • • . .. . . • • • . . 

• 

• 

• 

• 
• 


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