Mj. Roell et Dj. Orth, TROPHIC BASIS OF PRODUCTION OF STREAM-DWELLING SMALLMOUTH BASS, ROCK BASS, AND FLATHEAD CATFISH IN RELATION TO INVERTEBRATE BAIT HARVEST, Transactions of the American Fisheries Society, 122(1), 1993, pp. 46-62
We quantified annual consumption and annual production of the principa
l predatory fishes (smallmouth bass Micropterus dolomieu, rock bass Am
bloplites rupestris, and flathead catfish Pylodictis olivaris) in a 62
-hectare pool of the New River, West Virginia, to evaluate the potenti
al for competition among these species and people for crayfish (Cambar
us sciotensis, Orconectes sanbornii sanbornii, and Orconectes virilis)
and hellgrammite (Corydalus cornutus) resources. Production of smallm
outh bass (3.21 g-m-2.year-1), rock bass (2.00 g.m-2. year-1), and fla
thead catfish (0.56 g.m-2.year-1) was supported primarily by aquatic i
nsects (age-0 and age-1 fishes) and crayfish (age-2 and older fishes).
Hellgrammites were rarely eaten due to their secretive nature, and pr
ey fishes were less numerous than crayfish in the diets and the enviro
nment. Diet overlap among the three species was relatively high (Schoe
ner's overlap index = 0.74-0.93); species composition and sizes of cra
yfish eaten by the three fish species were similar. Smallmouth bass, r
ock bass, and flathead catfish consumed 35, 31, and 10% of the annual
production of age-1 and age-2 crayfish and less than 1, 13, and 1% of
the annual production of age-1 and age-2 hellgrammites. A bait fishery
harvested an additional 5% of crayfish production and 8% of hellgramm
ite production. Peak consumption by cohorts of all three fish species
occurred in August and September and was a function of survivorship, i
ncreasing individual fish size, and temperature-controlled energetic d
emand. Seasonal patterns of cohort production and biomass mimicked tre
nds in consumption. Peak fish production rates in late September were
a function of survivorship, increasing individual fish size, and high
rates of prey consumption. Cohort biomass accretion exceeded attrition
from mortality during most of the growing season, peaking in October.
Crayfish are critical prey for the smallmouth bass, rock bass, and fl
athead catfish populations in the New River. The sizes of crayfish eat
en by these fishes and harvested by people, the extent of use of crayf
ish production by these fishes and people, the crayfish species compos
ition in the diets of these fishes, the intensity of predation on cray
fish in late summer, and diet overlap suggest that competition among N
ew River fishes and people for the crayfish resource is intensive. Inc
reases in bait harvest or efforts to improve the quality of New River
sport fisheries would probably increase competition for the crayfish r
esource.