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Capture Efficiency of Blue Catfish Electrofishing and the Effects of Temperature, Habitat, and Reservoir Location on Electrofishing‐Derived Length Structure Indices and Relative Abundance
Author(s) -
Bodine Kristopher A.,
Shoup Daniel E.
Publication year - 2010
Publication title -
north american journal of fisheries management
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.587
H-Index - 72
eISSN - 1548-8675
pISSN - 0275-5947
DOI - 10.1577/m09-084.1
Subject(s) - electrofishing , catch per unit effort , catfish , ictalurus , fishery , habitat , environmental science , sampling (signal processing) , population , abundance (ecology) , biology , ecology , zoology , fish <actinopterygii> , physics , demography , detector , sociology , optics
Current sampling methods for blue catfish Ictalurus furcatus are suspected of being strongly biased against preferred‐length fish (≥762 mm in total length [TL]), making it difficult to accurately determine the species' population density and size structure. To understand this potential bias with respect to electrofishing, we conducted seasonal and habitat‐specific sampling on three Oklahoma reservoirs using 15‐pulse/s DC at the 100–1,000 V setting (the percent of range being adjusted to achieve 4‐A output). Temperature, habitat, and reservoir section were analyzed to determine which variables were associated with the highest total catch per unit effort (CPUE Total ), the CPUE of preferred‐length blue catfish (CPUE 762 ), and the relative stock density of preferred‐length fish (RSD 762 ). Total CPUE and CPUE 762 were significantly higher when the water temperature was 18°C or more, but the variability increased as the temperature exceeded 28°C. Catch rates were significantly higher in the upper reservoir section for all length‐groups, and no differences in CPUE Total were detected among habitats (channels, points, or flats). Both CPUE 762 and RSD 762 were highest in channel habitats, but the high variability and low catch rates of these larger fish limit the utility of habitat‐specific sampling based on these findings. Additionally, we evaluated the capture efficiency of electrofishing by creating a population with a known length‐frequency distribution. This population was sampled on three separate dates to determine which length‐groups were more vulnerable to electrofishing. No significant differences in catch rate were detected among the length‐groups, and the mean total catch from each sample was always less than 10% of the total population. Our results indicate that low‐frequency electrofishing is not size selective and provides representative samples of blue catfish between 200 and 1,000 mm TL. We recommend that sampling be conducted at temperatures between 18°C and 28°C and that standard sampling protocols adopt a stratified design that incorporates reservoir section.