Electrofishing catchability of walleye, largemouth bass, smallmouth bass, northern pike and muskellunge in Wisconsin lakes

We sought to determine whether electrofishing catchability was density dependent and varied with physical and biological factors for walleyes (Sander vitreus), largemouth bass (Micropterus salmoides), smallmouth bass (M. dolomieu), northern pike (Esox lucius), and muskellunge (E. masquinongy) in Wisconsin lakes. Electrofishing catch rate (number of fish caught per shoreline mile) was linearly related to population density (number of fish per acre) in spring for largemouth bass, northern pike, and muskellunge and in fall for walleyes, largemouth bass, and smallmouth bass. In contrast, gear saturation caused the electrofishing catch rate to be nonlinearly related (hyperstable) to population density for walleyes and smallmouth bass during spring. Catchability was higher during spring than fall for walleyes, largemouth bass, and smallmouth bass. Catchability of walleyes during fall was positively related to the percentage of littoral zone, whereas catchability of largemouth bass, smallmouth bass, and muskellunge was negatively related to the shoreline development index. Other physical and chemical variables failed to describe significant residual variation in catchability of any other species in any other season. We conclude that population density cannot be accurately estimated from the electrofishing catch rates of walleyes and smallmouth bass during spring. Therefore, mark–recapture methods must still be used to estimate population density if managers choose to sample those species during spring in Wisconsin lakes.