Injury of American Eels Captured by Electrofishing and Trap-Netting

Abstract

We compared the incidence of internal injuries in adult American eels Anguilla rostrata captured by trap-netting (N = 20) and by 30-Hz, pulsed-DC electrofishing (N = 18) in the St. Lawrence River, New York. On average, the lengths and weights of fish caught by the two methods were similar. Radiographic imaging revealed that spinal damage occurred in 60% of the electroshocked American eels but only 15% of the trap-netted American eels. Bilateral filleting showed hemorrhages in 30% of the electroshocked fish but none of the trap-netted fish. Electrofishing caused significantly higher incidences of both spinal damage and hemorrhage than did trap-netting. Most electroshocked American eels had multiple spinal injuries; hemorrhages occurred only in fish with multiple sites of vertebral damage. We recommend that workers avoid the use of 30-Hz, pulsed DC to capture American eels that are intended for release; a lower frequency, such as 15 Hz, may significantly reduce injury but may also result in unacceptably low capture rates. We hypothesize that electroshocked American eels are at high risk for injury because of their large size (>90 cm) and high vertebral count (>100).