Capture Efficiency and Size Selectivity of Channel Catfish and Blue Catfish Sampling Gears

Abstract

We used proportional recapture data from mark–recapture experiments to directly estimate capture efficiency (percentage of fish captured per standard level of effort) and size selectivity (for 50-mm size-groups) of catfish sampling gears. Hoop-net series were evaluated for collecting channel catfish Ictalurus punctatus, and low-frequency, pulsed DC electrofishing was evaluated for collecting blue catfish I. furcatus. To examine spatial and temporal variability, capture efficiency and size selectivity were estimated in river and reservoir habitats during June, July, and September 2005. Selectivity of experimental gill nets was also assessed. Capture efficiency of hoop nets for channel catfish was consistent across months and between river and reservoir habitats (2.7–14.3% per 12 hoop-net series). Capture efficiency of low-frequency electrofishing was low (frequently, ≤1% per 120 min) and variable; recapture rates were greatest in river habitat during July and September. Hoop-net series collected representative samples of channel catfish between 250 and 556 mm total length. Likewise, blue catfish between 250 and 855 mm were fully vulnerable to low-frequency electrofishing. Although fish smaller than 250 mm were captured, they were frequently underrepresented in the catch of both gears. Size selectivity was not affected by habitat or month sampled for either gear type or either species. Capture efficiency of experimental gill nets was very low for both channel catfish and blue catfish (about 0.2% in 46 gill-net nights), and gill nets were more size selective than other gears. Based on our findings, hoop-net series and low-frequency electrofishing provide accurate size structure data for adult channel catfish and blue catfish, respectively, from both river and reservoir habitat types. Hoop-net series also provide consistent estimates of channel catfish relative abundance; however, relative abundance data for blue catfish collected with low-frequency electrofishing should be used with caution due to observed variability in capture efficiency.