Effects of Chase Boat Use, Electrofishing Duration, and Water Velocity on Sample Efficiency and Size Structure of Blue Catfish

Abstract

AbstractChase boats are used to assist in the capture of Blue Catfish Ictalurus furcatus because they often surface relatively far from the electrofishing boat (electrofisher) when incapacitated by low‐frequency, pulsed DC. We conducted this study to determine how chase boat use affects size‐related and capture efficiency metrics of Blue Catfish, and we concurrently examined possible confounding effects of sample duration and velocity on these metrics. We used DC at 15 pulses/s in 5‐ or 10‐min runs during four trials that were stratified by reservoir zone, season, and macrohabitat over a 2‐year period in Pool 10 of the Arkansas River (Lake Dardanelle, Arkansas). We captured 4,330 fish in 96 samples and analyzed the catch data by size‐group (all fish; >199, >299, and >509 mm). We compared samples of fish captured by an electrofisher alone with those collected by the electrofisher in combination with a chase boat (chase+). The electrofisher‐only protocol captured a greater proportion of fish less than 300 mm compared to the chase+ protocol, but length‐frequency distributions of larger‐size fish did not differ. Overall catch was greater for the chase+ protocol, with the difference generally increasing by size‐group except for the largest fish. Catch efficiency was greater for 5‐ versus 10‐min samples for both protocols, with the relative difference increasing as fish size increased. Calculated values of the proportional size distribution of quality‐size fish were sufficiently similar among all combinations of protocol and duration for management purposes. The practical implication is that an electrofisher‐only protocol can be used to collect representative samples of Blue Catfish, but the use of a chase boat increases the average catch per boat.