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).

Behavioral and Physiological Response of White Sturgeon to an Electrical Sea Lion Barrier System

“…An electrical sea lion barrier system creates an electrical field within the water column to deter California sea lion movement upstream. The system is designed to operate at electrical power levels far below guidelines established by state and federal agencies for electrofishing of salmonid fishes (NMFS 2000;WSDOT 2006), and the system uses a pulsed direct current (DC) frequency lower than 15-30 Hz, which is intended to minimize injury to nontargeted fish (Reynolds 1996;Reynolds and Holliman 2004). Nevertheless, given that electrical fields have been applied in North America since the 1950s to alter and Subject editor: Tim Essington, University of Washington, Seattle preclude the movement of aquatic fish species (Applegate et al 1952;McLain et al 1957;Swink 1999;Clarkson 2004), concerns have arisen among regulatory personnel and fisheries biologists regarding the effects that even a relatively low electrical field may have on nontarget species migrating through or residing within sites where such a system is tested or constructed.…”

Shocking Results: Assessing the Rates of Fish Injury from Pulsed‐DC Electrofishing

“…Reynolds and Holliman (2004) also reported an injury rate of 60% for American Eels Anguilla rostrata captured via PDC electrofishing in the St. Lawrence River, New York. With the exception of the Reynolds and Holliman (2004) study, all of the PDC electrofishing studies on nonsalmonid fishes have been conducted in laboratory settings, demonstrating a critical need for in situ studies that further investigate the effects of PDC electrofishing on fish.…”

“…Several laboratory studies have documented injury rates as high as 90% and mortality rates as high as 60% for warmwater fish exposed to PDC electrofishing (Dolan et al 2002;Henry and Grizzle 2003;Miranda and Kidwell 2010). Reynolds and Holliman (2004) also reported an injury rate of 60% for American Eels Anguilla rostrata captured via PDC electrofishing in the St. Lawrence River, New York. With the exception of the Reynolds and Holliman (2004) study, all of the PDC electrofishing studies on nonsalmonid fishes have been conducted in laboratory settings, demonstrating a critical need for in situ studies that further investigate the effects of PDC electrofishing on fish.…”

Physical Injuries in Juvenile Atlantic Salmon, Slimy Sculpin, and Blacknose Dace Attributable to Electrofishing

“…In contrast to the alarmingly high injury rate observed in large salmonids, negligible (,5%) electrofishing-induced spinal injuries, hemorrhages, or both were found in largemouth bass Micropterus salmoides, smallmouth bass M. dolomieu, bluegill Lepomis macrochirus, pumpkinseed L. gibbosus, roundtail chub Gila robusta, least cisco Coregonus sardinella, humpback whitefish C. pidschian, spotfin chub, and Cape Fear shiners (Spencer 1967;Holmes et al 1990;Cowdell and Valdez 1994;Bardygula-Nonn et al 1995;Holliman et al 2003aHolliman et al , 2003b. However, Reynolds and Holliman (2004) observed that electrofishing using pulsed DC (30 Hz) inflicted spinal injuries in 60% and hemorrhages in 30% of American eels Anguilla rostrata (mean TL 6 SD ¼ 91.7 6 8.1 cm).…”

“…The harmful effects of electrofishing on salmonids was identified by Hauck (1949), but serious concerns about the deleterious effects of electrofishing on fish arose principally during the late 1980s and 1990s (Gatz et al 1986;Sharber and Carothers 1988;Mesa and Schreck 1989;Hollender and Carline 1994;Dalbey et al 1996). The current state of knowledge on the effects of electrofishing has extended in recent years to include additional fish species (e.g., Reynolds and Holliman 2004;Gatz and Linder 2008;Bohl et al 2009).…”