Diel Differences in Electrofishing Catch in the Atchafalaya River Basin, Louisiana

Published reports indicate night electrofishing may be superior to day sampling to estimate density and diversity of collected shes in some aquatic habitats. However, because shallow, highly turbid waters characteristic of river floodplains present fish detection, navigation, and safety concerns during night electrofishing, many southeastern floodplain sampling programs have focused on day electrofishing. We used paired day and night samples of shes collected by transect (200 m distance for eight minutes) and point electro fishing (1 minute at four points spaced 25 m apart) to assess potential day electro fishing bias at four sites in the Atchafalaya River floodplain during fall and winter 2013. Analyses compared day and night estimates of overall catch-per-unit e ort (CPUE) of bluegill (Lepomis macrochirus), largemouth bass (Micropterus salmoides), and black crappie (Pomoxis nigromaculatus), as well as species richness and assemblage evenness by electrofishing method. Point sampling at night resulted in greater overall and bluegill CPUEs, with transect electrofishing yielding greater nighttime richness and daytime largemouth bass CPUE. No differences were detected for estimates of black crappie CPUE, evenness, or between day and night assemblages for either sampling method. Selection of day or night electro fishing depends on sampling goals, habitat characteristics, particularly turbidity, and the electrofishing method employed, but our data indicate that daytime sampling provides acceptable estimates of fish assemblage structure in the Atchafalaya River floodplain.

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