| Abstrakt: |
We quantified annual consumption and annual production of the principal predatory fishes (smallmouth bass Micropterus dolomieu, rock bass Ambloplites rupestris, and flathead catfish Pylodictis olivaris) in a 62-hectare pool of the New River, West Virginia, to evaluate the potential for competition among these species and people for crayfish ( Cambarus sciotensis, Orconectes sanbornii sanbornii, and Orconectes virilis) and hellgrammite ( Corydalus cornutus) resources. Production of smallmouth bass (3.21 gṡm-2ṡyear-1), rock bass (2.00 gṡm-2ṡyear-1), and flathead catfish (0.56 gṡm-2ṡyear-1) was supported primarily by aquatic insects (age-0 and age-1 fishes) and crayfish (age-2 and older fishes). Hellgrammites were rarely eaten due to their secretive nature, and prey fishes were less numerous than crayfish in the diets and the environment. Diet overlap among the three species was relatively high (Schoener's overlap index = 0.74-0.93); species composition and sizes of crayfish eaten by the three fish species were similar. Smallmouth bass, rock 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 hellgrammite production. Peak consumption by cohorts of all three fish species occurred in August and September and was a function of survivorship, increasing individual fish size, and temperature-controlled energetic demand. Seasonal patterns of cohort production and biomass mimicked trends 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 flathead catfish populations in the New River. The sizes ofcrayfish eaten by these fishes and harvested by people, the extent of use of crayfish production by these fishes and people, the crayfish species composition in the diets of these fishes, the intensity of predation on crayfish in late summer, and diet overlap suggest that competition among New River fishes and people for the crayfish resource is intensive. Increases in bait harvest or efforts to improve the quality of New River sport fisheries would probably increase competition for the crayfish resource. [ABSTRACT FROM AUTHOR] |
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