The relationship between forage base and trout production in catch and release areas on Bull Shoals and Norfork tailwaters.
July 2004 - July 2008
- Arkansas Game and Fish Commission
Catch-and-release regulations are commonly used in sport fisheries in an attempt to provide increased residence times and survival rates and provide more and/or larger fish. Most catch-and-release studies address factors that affect immediate mortality rates in fish, but rarely evaluate fish growth rates and food resources. We used a bioenergetics modeling approach to examine whether food resources limited brown and rainbow trout production in three catch-and-release areas in Bull Shoals and Norfork tailwaters. We incorporated field data on brown and rainbow trout thermal experience, growth, diet analysis, and abundance from catch-and-release areas into species-specific bioenergetics models to quantify seasonal consumption of benthic fish and drifting invertebrates and compared prey consumption rates to prey availability. Growth rates were reduced in fall and winter for both species, indicating a possible seasonal bottleneck in prey supply. Based on diet analysis, Amphipoda, Chironomidae, Cladocera spp., Decapoda, Gastropoda, Isopoda, and sculpin were commonly ingested by brown and rainbow trout, but varied by species, season, and site. Despite the lack of energetic value to trout, filamentous algae was also found in stomachs of rainbow trout in high proportions at each site across all seasons, indicating epibenthic foraging. Sculpin became more common in the stomachs as brown trout attained larger sizes (>250 mm), indicating a shift to piscivory with size. Abundances of trout in Norfork C-R were nearly twice as high as Bull Shoals. Food limitation for rainbow trout appeared to occur in fall/winter, whereas brown trout were typically not food limited. Norfork CR area supported higher consumption, growth rates and densities than Bull Shoals for both species, and Bull Shoals prey base was adequate to maintain or support brown trout growth. This information will assist managers in determining the effectiveness of the catch-and-release areas in Arkansas tailwaters.