Escapement of Fishes from Modified Fyke Nets with Differing Throat Configurations
We performed a field experiment in five eastern South Dakota lakes to investigate fish escapement differences between modified fyke nets with two common throat configurations (restricted and unrestricted). Nets with restricted and unrestricted throats were deployed in pairs for 24 h on similar habitat. Captured fish were measured for TL and were given day-specific marks. The paired nets were redeployed, and marked fish were randomly assigned to be stocked into the restricted or unrestricted net for 24 h; stocking densities (stratified into low, medium, and high) were species specific. Marked fish that were retained after 24 h were used to quantify escapement, whereas newly captured fish were used to estimate differences in mean CPUE and size structure. Mean CPUE of Black Bullheads Ameiurus melas, Black Crappies Pomoxis nigromaculatus, and Bluegills Lepomis macrochirus approximately doubled when restricted nets were used. Mean TL of Black Crappies was 31 mm greater (95% confidence interval [CI] = 6–57 mm greater) and mean TL of Bluegills was 21 mm greater (95% CI = 8–35 mm greater) in restricted nets than in unrestricted nets. Escapement from restricted nets was 4.4% for Black Crappies and 10.3% for Bluegills, whereas escapement from unrestricted nets was 71.7% for Black Crappies and 58.4% for Bluegills. We urge researchers to consider the influence of varying fyke-net throat configurations on calculated population metrics, and we recommend inclusion of the restricted throat feature in gear specifications for North American standard modified fyke nets.