Impacts of Commercial Harvest of Invertebrate Baits on the Predator-Prey Interactions in the New River
Roell MJ and Orth DJ. 1988. Impacts of Commercial Harvest of Invertebrate Baits on the Predator-Prey Interactions in the New River. Virginia Polytechnic Institute and State University. Blacksburg, VA
The dynamics of the hellgrammite population (Coryda/us cornutus larvae) and three crayfish populations (Orconectes virilis, Cambarus sciotensis, and Orconectes sanbornii sanbornii) were assessed in the New River, West Virginia, between Bluestone Dam and Sandstone Falls. Quadrat sampling, qualitative collections, and laboratory analytical procedures were used to estimate abundance, age and growth, and production. Mean abundance of hellgrammites was 1.3/m2, and, as expected, abundance in riffles (1.4/m2) was greater than in pools (0.1/m2). Larvae were more numerous in the lower portion of the reach (2.0/m2) than immediately below the dam (1.0/m2). Annual production (age 1 and 2 larvae only) in the reach was 3.1 g/m2 (wet weight). Production in riffles and pools was 6.0 and 0.3 g/m2, respectively; surface areas of riffles (197 ha) and pools (211 ha) were nearly equal. Annual mean biomass of age 1 and 2 larvae in the reach was 1.3 g/m2, and the production / mean biomass ratio was 2.41. Larvae of about 6 mm head capsule width or greater were considered marketable by bait dealers. The estimated annual mean abundance of marketable-sized hellgrammites in the study reach was 4.65 million larvae. Anglers and commercial bait dealers harvested about 8% of the annual production of age 1 and 2 hellgrammites. Crayfish mean abundance was 2.7/m2, and abundance in riffles (2.8/m2) was greater than in pools (1.2/m2). Densities were slightly greater in the lower portion of the reach (3.5/m2) than below the dam (2.7/m2). 0. virilis was the most abundant (1.3/m2) in riffles; C. sciotensis dominated pools (l.l/m2), especially deeper (1 - 3 m) areas. Relative abundances of the three species in deep versus shallow (< 1 m) areas of a pool suggested habitat partitioning. Total annual crayfish production (age 1 and 2 crayfish only) in the reach was 10.4 g/m2 (wet weight). Production in riffles and pools was 12.7 and 8.3 g/rn2, respectively. Annual mean biomass estimates (age 1 and 2 combined) for the reach were 0.7 g/m2 for 0. virilis, 2.3 g/m2 for C. sciotensis, and 0.7 g/m2 for’O. s. sanbornii, and respective production / mean biomass ratios were 2.37, 2.89, and 3.05. Crayfish of about 20 mrn carapace length were considered marketable by retailers, and the annual mean abundance of marketable-sized crayfish in the reach was 4.08 million animals. Approximately 4% of the annual production of age 1 and 2 crayfish was harvested by commercial retailers and anglers.
- Type
- Published Report
- Authors
- Roell, Michael; Orth, Donald
- Date of Issue
- 1988
- Publisher
- Virginia Polytechnic Institute and State University
- Units
- NERI
- Keywords
- Animal Studies, bait, Cambarus sciotensis (crayfish), Fishing, hellgrammites (Corydalus cornutus), Human Impact, Orconectes sanbornii sanbornii (crayfish), Population Dynamics, virile crayfish (Orconectes virilis)