14 
feed on mayfly larvae and pupae, dragonfly larvae, 
Chironomus \arvae, and water bugs (Corixa sp.) 
(Forbes & Richardson 1920:286). Our examination of 
stomachs of P. phoxocephala in the Embarras River 
revealed a diet similar to that of P. sciera, but it in- 
cluded a greater variety of items. Some competition 
between the two species was suggested, but whether or 
not the food supply ever became low enough to cause 
population-limiting competition (demand in excess of 
supply) could not be ascertained. Collections of P. 
sciera examined throughout the year contained at least 
some specimens with full stomachs and thus competition 
for food was probably not a limiting factor for popula- 
tions of P. sciera. 
Competition for habitat space between P. sciera 
and most other darters occurring in the study area was 
also probably minimal because of differences in pre- 
ferred microhabitat. For example, Etheostoma blen- 
nioides and E. caeruleum selected shallower, faster, and 
more rocky riffles. E. nigrum and Percina maculata 
preferred pools or slow-flowing raceways with sandy 
or silty bottoms. Etheostoma spectabile, which prefers 
headwaters and small tributaries, was uncommon in 
the river. Ammocrypta pellucida was rigidly restricted 
to sand-bottom areas. Percina caprodes and Etheostoma 
histrio, somewhat similar to one another in their habitat 
requirements in the Embarras River, selected fairly 
deep, rapid-flowing water with brush or debris on the 
bottom. Other species of darters were present in the 
study area only in extremely small populations. 
However, P. sciera and P. phoxocephala appeared 
to be somewhat competitive for habitat and possibly 
breeding space inasmuch as they were the two most 
abundant darters in the study area and frequently were 
found together. P. phoxocephala is more plastic in its 
microhabitat choices, sometimes occupying swift water 
over sand, silty-sand bottom, or shallow riffles. 
Competition for breeding sites was not likely among 
darters in the study area, inasmuch as, so far as breeding 
habits are known, all species except P. phoxocephala 
bred earlier than P. sciera. 
Predation 
No evidence of predation on dusky darters was 
found. By far the most abundant, large predaceous fish 
in the study area was the spotted bass, Micropterus 
punctulatus. Concurrent with the life-history study of 
the dusky darter, an investigation of the feeding habits 
of the spotted bass was conducted. The stomachs and 
intestines of 114 bass of various sizes were examined, 
and the only predation on darters noted was the remains 
of three specimens of Etheostoma nigrum (Smith & 
Page 1969). 
Parasitism 
A high incidence of leech parasitism was noted on 
dusky darters from June to November in the study area. 
A total of 109 leeches was removed from 249 darters 
examined for ectoparasites, most often from the proxi- 
mal portion of the caudal fin. The leeches, identified as 
Piscicolaria reducta Meyer by Dr. M. C. Meyer, were 
more numerous on large darters, some having as many 
as four leeches. The number of leech parasites per fish 
on young darters examined was .39 (215 fish), on 
yearlings .57 (31 fish), and 2-year-olds 2 (3 fish). 
No other external parasites were noted. 
Hybridization 
Hybridization involving the dusky darter has been 
recorded in nature and as a result of experimental 
laboratory crosses. Hybrids between the dusky darter 
and blackbanded darter (Percina nigrofasciata) were 
reported by Suttkus & Ramsey (1967:141) from the 
Pearl River in Louisiana, and between the dusky darter 
and logperch (Percina caprodes) by Hubbs & Laritz 
(1961la) from the San Gabriel River in Texas. Also, 
an intergeneric hybrid between the dusky darter and 
orangethroat darter (Etheostoma spectabile) was re- 
ported by Hubbs & Laritz (1961b) from the San 
Marcos River in Texas. 
Clark Hubbs and his students at the University of 
Texas have made artificial intergeneric and interspecific 
crosses involving the dusky darter and several other 
species of Percina and Etheostoma (Hubbs 1959; 
Hubbs & Strawn 1957). 
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LITERATURE CITED 
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SMITH. 1954. Fishes from the Escambia River, Alabama 
and Florida, with ecologic and taxonomic notes. Academy 
of Natural Sciences of Philadelphia Proceedings 106: 
109-164. 
BLAIR, ALBERT P. 1959. Distribution of the darters (Percidae, 
Etheostomatinae) of northeastern Oklahoma. Southwest- 
ern Naturalist 4(1):1—13. 
BRAASCH, MARVIN E., and Puitie W. Smit. 1967. The life 
history of the slough darter, Etheostoma gracile (Pisces, 
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COLLETTE, BRUCE B. 1965. Systematic significance of breed- 
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FAHY, WILLIAM E. 1954. The life history of the northern 
greenside darter Etheostoma blennioides blennioides Ra- 
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ForRBES, STEPHEN ALFRED, and ROBERT EARL RICHARDSON. 
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