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Tuesday, January 30 • 3:20pm - 3:40pm
SYMPOSIA-07: Evaluation of Four Modified Fyke Net Designs for Standard Fish Sampling

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AUTHORS. Rebecca M. Krogman, Iowa Department of Natural Resources

ABSTRACT. Modified fyke nets are used across the U.S. for panfish sampling in lentic waters, including lakes and reservoirs in Iowa.  However, modified fyke net designs in Iowa, like many states, differed substantially from the standard set forth by the American Fisheries Society (AFS).   Traditional modified fyke nets in Iowa differed from the AFS standard in two primary ways: throat opening design and number of throats.  Given the historical datasets derived from traditional nets and the reticence to convert to a net with lesser performance, an evaluation of net designs was needed.  Four combinations of throat design (open or crowfoot-style) and number of throats (one or two) were examined in this study.  The objective was to identify the modified fyke net design with the highest catch and retention rates of target species, including crappies Pomoxis spp., Bluegill Lepomis macrochirus, and Redear Sunfish L. microlophus.  For retention, nets were stocked with marked target fish and set overnight, then checked for retained fish the following morning.  Fish escapement by net type and species was analyzed using Cochran-Mantel-Haenszel tests and relative risk.  For catch efficiency, nets that were not pre-stocked with fish were deployed concurrently according to standard protocol.  Catch rates from these net sets were compared using generalized linear mixed models predicting catch with net design as a fixed effect and site nested within lake as a random effect.  Net design was a significant factor affecting both retention and catch efficiency, with the traditional Iowa net outperforming all other designs.  Modeling was then used to estimate the number of net sets needed for adequate sampling power using the recommended net design.  Standard modified fyke net sampling in Iowa will be adjusted according to these recommendations and should be considered elsewhere.

Tuesday January 30, 2018 3:20pm - 3:40pm CST