Extending the Effectiveness of Electrofishing to Estuarine Habitats: Laboratory and Field Assessments

Abstract

Electrofishing is a widely used and highly effective method of sampling freshwater fishes. However, power limitations currently restrict electrofishing to waterways with ambient electrical conductivities up to 5,000 μS/cm. At these higher conductivities, the electrofishing devices currently available are limited in providing the peak power required for effective electrofishing (i.e., peak power drops below the fish capture threshold). The Grassl Model EL65IIGI1 electrofisher (GEF) is a new, high-power boat electrofishing system designed to successfully fish waters with electrical conductivities exceeding 5,000 μS/cm, but its electrical output and effective power range for fish capture remain untested. We used tank and field electrical load tests to document the output power capability of the GEF over a wide range of electrical resistances and conductivities. Maximum power output for the low voltage range was 246,500 peak watts, with a maximum current of 1,880 peak amperes. Effective fish capture conductivity for the GEF with standard electrodes was estimated to range from 30 to 35,000 μS/cm. Our results demonstrate that the GEF greatly extends electrofishing capability into estuarine and brackish-water habitats.