Escapement of Fishes from Modified Fyke Nets with Differing Throat Configurations

Modified fyke nets are commonly used to sample fishes in freshwater but few studies have investigated potential bias resulting from use of differing throat configurations, namely restricted forms that include a cone-like apparatus constructed of twine and unrestricted forms that lack such an apparatus.  To fill this information gap we performed a paired gear comparison and subsequent density-dependent escapement trials to identify species-specific differences in 24-hr retention and escapement, catch per unit effort (CPUE), and sizes of collected fish between North American Standard modified fyke nets with and without restricted throat configurations.  Restricted nets yielded higher CPUE for stock-length Black Crappie Pomoxis nigromaculatus and Bluegill Lepomis machrochirus and 24 hr retention was high (≥ 90%) for both species.  Conversely, unrestricted nets yielded lower estimates of CPUE for stock-length Black Crappie and Bluegill and 24 hr retention was low (<42%) for both species.  Restricted nets were selective for larger Black Crappie and Bluegill.  When using and reporting gear specifications for modified fyke nets we urge researchers to consider the influence of varying throat configurations on calculated population metrics and recommend inclusion of this feature in gear specification for North American Standard modified fyke nets.