Selectivity of Sampling Methods for Juvenile Largemouth Bass in Assessments of Recruitment Processes

Assessment of the recruitment processes of juvenile largemouth bass Micropterus salmoides has involved a variety of gears, and little consideration has been given to the biases that gear size selection may introduce. To determine the influence of collecting methods on the interpretation of cohort characteristics, we compared length distributions of juvenile largemouth bass collected with a 9-m bag seine, a hand-held electrofisher, and a traditional boom-mounted electrofisher. The hand-held electrofisher was effective for sampling all lengths of fish up to 200 mm total length and sampled smaller fish than the boom-mounted unit. Seining was effective for sampling fish shorter than 60 mm but, relative to the hand-held electrofisher, it consistently underrepresented the contribution of fish longer than 70 mm to the cohort. The boom-mounted electrofisher was effective at sampling fish longer than 150 mm, but, compared with the hand-held electrofisher, it underestimated the contribution of smaller fish to population size structure. Gear selectivity may bias assessments of the importance of abundance and size to recruitment of juvenile largemouth bass.