12 
TapiE 9.— Comparison of foods of young and adults 
percent of stomachs examined containing the item listed. 
which contained that item. 
of three species of Percina at the Sullivan station. 
“Average number’ is the average number of items found in stomachs 
“Frequency” is the 
Thin Conn ee ee 
P. maculata P. phoxocephala P. caprodes 
a a ae 
Young Adult Young Adult Young Adult 
(43) (22) (11) (27) (7) (22) 
Av. Av. Av. Av. Av. Av. 
Freq. No. Freq. No. Freq. No. Freq. No. Freq. No. Freq. No, 
Diptera 
Chironomidae 88.4 13.5 Ui) 
Simuliidae 34.8 8.5 ied) 
Diptera pupae 37528 31.8 
Diptera adults 2 Smee tO 
Ephydridae sek 
Anthomyiidae 4.5 
Rhagionidae as 
Ceratopogonidae 4.5 
Ephemeroptera 
Baetidae 4179 7.8 54.5 
Heptageniidae 18) 65ne2e8 36.4 
Caenidae Da PEs om 
Ephemeridae Su re rae 
Miscellaneous 70 MWe 4.5 
Trichoptera 
Hydropsychidae oy Be 18.2 
“Case builders” 13.6 
Plecoptera 
Odonata 
Zygoptera-Coeragrionidae 
Coleoptera 
Elmidae - 
Haliplidae 4.5 
Gastropoda 
Ancylidae 
Crustacea 
Copepoda SVL PA” 2S 
Cladocera Wace) Goi 13.6 
Ostracoda 457 ge le ae 
Fish eggs be su 4.5 
Insect eggs Pare Abel) g).. il 
Sand grains TPO)? Mater) Peed | 
Plant material 4.7 1.9 4.5 
(Empty) 
of an overwhelming majority of animals, biotic factors 
were of decisive importance and that, among these 
biotic factors, feeding conditions occupied an excep- 
tional position. He found definite preference /avoidance 
patterns in food habits of certain fish and noted that a 
decrease in need for food resulted in increased selectivity 
for preferred forms of food. 
There was some evidence of selective feeding in 
species of Percina. Elmid beetle adults and _ stonefly 
nymphs which were often abundant in riffles were gen- 
erally avoided by the darters. Also, P. maculata took 
a preponderance of chironomids and simuliids in the 
spring, even though other groups of food organisms 
were common. Certain groups of organisms (such as 
Chironomidae) made up an important part of the 
diet in all Percina studied although different species of 
— 
Dao 
100.0 5.2 44.4 2.4 100.0 36.9 100;0mmmm 
Sy agi ~ aber 82 |: Cl 
74 41.5 57.1 13.3 Soa 
an 
i4-3 
9.1 ae 
0 
36.4 3.3 29.6 2.4 57.1 3.5 | sec 
a6 42200 25.9 1.3 14.3 1.0 cc 
91 1.0 11.1 1.0 42.9 3.3) cn 
i jae IO » % 
O gil 7210 aie 4ee neo 4.5 
3 96.4 «4.0 44.4 4.3 42.9 17.7 Sa 
0 18.2 1 
13.6 
28.6 1.0 
; 28.6 2.0 18.2 1 
0 
57.1 7.0 59.1 6 
7 49.9 4.3 Ooi 
0 57.1 1.8 13.6 1 
Five Ee dial é. 
0 ae " "13am 
A. 18.9 2,0 57.1 5.5 63.66 
0 “ 29.7 1 
14.8 
larvae were eaten in different habitats and in differe 
sections of the river. 
GROWTH AND POPULATION STRUCTURE 
All fish were aged by the scale method. Back-calc 
lations of length at each annulus were made from t 
logarithmic regression of scale length to body leng' 
The following regression equations were used: P. mac 
lata (Log Y = -0.3885 + 1.0449 Log X), P. phoxo 
phala (Log Y = -0.3530 + 1.0166 Log X), P. caproé 
(Log Y = -0.8150 + 1.2654 Log X), and P. shuma 
(Log Y = -0.1229 4 0.9397) Log X), wheres ae 
times the anterior radius of the scale in millimet 
and X = total length of the fish in millimeters. 
Length-weight relationships were determined by | 
