Assessing Shad Abundance: Electrofishing with Active and Passive Fish Collection

Abstract

Abstract We compared electrofishing samples collected with a push net to those collected by dipnetting. Catch per unit effort (CPUE) of threadfin shad Dorosoma petenense and of gizzard shad D. cepedianum 150 mm total length or shorter did not differ between collection methods, although more gizzard shad larger than 150 mm were collected by dipnetters than were collected with the push net. The precision of CPUE estimates differed between gears and between species. To obtain a target coefficient of variation of the mean (CV X = 100 × SE/mean) of 20% for threadfin shad, dipnetting required 5–7 more person-hours than did electrofishing with the push net. However, for gizzard shad 150 mm or shorter the push net required up to 1.0–1.4 more person-hours than dipnetting. Results for gizzard shad longer than 150 mm were mixed between sites. The push net may provide an acceptable alternative to dipnetting for sampling inshore shad populations, particularly in systems dominated by small shad.