Use of a chase boat for increasing electrofishing efficiency for flathead catfish in lotic systems

Chase boats are commonly used to increase the catch efficiency of boat electrofishing for flathead catfish Pylodictis olivaris. However, use of a second vessel requires additional personnel, equipment, and budgetary resources that may influence decisions regarding sample planning efforts. While the efficacy of chase boats has been examined for lentic environments, no such Studies have been documented for lotic systems. During 2002 and 2003, we compared low-voltage electrofishing catch efficiency with and without the use of a chase boat for three flow-rate classes in the lower St. Joseph River, Michigan. The median percentage of flathead catfish captured was significantly greater when a chase boat was used (60% of immobilized fish observed) than when a chase boat was not used (33%) at sampling locations with moderate flow rates (0.31-0.6 m/s). However, the catch efficiency with and without the use of a chase boat did not significantly differ at sampling locations with low (0-0.3-m/s) and high (>0.6-ni/s) flow rates (range, 50-70%). Length-frequency distributions of flathead catfish were not significantly different between samples collected by electrofishing with or without a chase boat. Our results suggest that study objectives should be considered when determining whether to use a chase boat while boat electrofishing for flathead catfish in lotic systems.