Heaviest feeding occurred during May, just before 
the spawning period. Although feeding was reduced in 
winter as Fahy (1954:152) found in adult Etheostoma 
blennioides, some food ingestion probably occurs 
throughout the year. The deposits of fat around the 
intestine were approximately the same all year, except 
for the prespawning period during which time the 
gonads were developing and the amount of stored 
adipose tissue diminished. After spawning, the fat 
reserve was gradually replenished. 
As the darters increased in size, there was a change 
100 
90 
80 
MIDGE LARVAE 
70 
60 
50 
40 
30 
PERCENT OF FOOD ITEMS 
20 
30- 35- 40- 45- 50- 
55- 60- 65- 70O- 75- 
Somes 45) 50) 55 60 65 70 75 £480 
STANDARD LENGTH, mm 
Fig. 10. — Change in relative consumption of midge lar- 
vae and caddisfly larvae as Percina sciera increases in size. 
13 
in the over-all diet composition (Fig. 10). In fish less 
than 65 mm standard length, midge larvae were the 
predominant food item; caddisflies were seldom eaten. 
However, in fish 65-80 mm, the diet consisted pri- 
marily of caddisfly larvae. The average length of all 
darters containing caddisfly larvae was 63.5 mm, and 
for those containing dipteran larvae it was 50.1 mm. 
The proportion of mayflies and other miscellaneous 
food items was about the same in both small and large 
darters. 
No data are available for the food of recently 
hatched young. In this study the smallest young con- 
tained dipteran larvae like those found in larger fish. 
However, the newly hatched darter, because of its small 
size, must feed for a time on plankton and other micro- 
organisms, as the hatchlings of other darters are known 
to do (Braasch & Smith 1967:11). The main criteria 
determining differences between the diets of young and 
adult fish (Fig. 11) appear to be the size and avail- 
ability of the prey item. 
Aquarium-held specimens of P. sciera readily fed 
on mosquito wrigglers, phantom midge larvae, and 
sections of small earthworms. 
INTERACTIONS WITH OTHER ORGANISMS 
Competition 
Limited information is available on the feeding hab- 
its of several of the fish species living in the study area. 
However, only those maintaining sizeable populations 
in the same habitat as the dusky darter needed to be 
considered as important competitors for food. The 
most likely of these was the slenderhead darter, Percina 
phoxocephala, which was rather abundant in much the 
same habitat and had a diet somewhat similar to that of 
the dusky darter. Slenderhead darters were noted to 
Fig. 11.—Composition of the diets of juve- 
nile and adult Percina sciera collected in the 
study area from August 4, 1967, to July 7, 
1968. 
