Electroshock-Induced Injury in Juvenile White Sturgeon

Abstract

Most sturgeon (Acipenseridae) populations are threatened or depleted. Assessment operations that could harm individuals in these populations, such as electrofishing, must be evaluated. The risk of electrofishing-induced injury in juvenile white sturgeon Acipenser transmontanus associated with electrical waveform (60-Hz pulsed DC [PDC] versus DC) and fish size (small [24-33 cm], age 1 versus large [37-54 cm] age 2) was evaluated in a tank experiment. Exposure to a homogeneous electric field of 1.2 V/cm immobilized all white sturgeons exposed to electrical treatments. No injury was found in the control groups. The risk for hemorrhage was significantly greater among white sturgeons exposed to PDC than among those exposed to DC (relative risk ϭ 6.7; 95% CI ϭ 3-29). Both size-groups were at significantly more risk for hemorrhage when exposed to PDC than to DC. All white sturgeons exposed to DC recovered (upright orientation and normal swimming) in less than 30 s; 95% recovered immediately. Most large sturgeons exposed to PDC required 1-2 min for recovery; most small sturgeons recovered immediately. Our results suggest that if electrofishing is conducted in waters where imperiled populations of white sturgeons are present, DC should be considered for use instead of 60-Hz PDC. If 60-Hz PDC must be used, electrofishers should be aware that a substantial portion of fish immobilized (complete cessation of movement) while electrofishing will probably be injured (hemorrhages). Results from other studies indicate that the incidence and severity of injury from PDC electrofishing can be reduced by using lower voltages and pulse frequencies (e.g., 60 Hz to 20-30 Hz) while maintaining capture responses less severe than immobilization (e.g., galvanotaxis).

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

“…Fish were immediately euthanized with an overdose of tricaine methanesulfonate (MS-222) and refrigerated for a 24-h period to reduce fillet-related bleeding. Because white sturgeon skeletons are not visible on radiographs, the severity of injury was evaluated by filleting both sides of each fish to expose axial skeleton and musculature following the methods of Reynolds (1996) and Holliman and Reynolds (2002). The notochord was separated and visually examined for damage (i.e., notochord rupture).…”

“…Lethal effects may result from electrical burns, hemorrhaging, and spinal and notochord injuries (Sharber and Carothers 1988;Hollender and Carline 1994;Sharber et al 1994;Reynolds 1996;Schill and Elle 2000;Holliman and Reynolds 2002;Snyder 2003); however, electroshock may be administered at levels chosen to minimize injury to adult fish (Holliman and Reynolds 2002;Zydlewski et al 2008). Nevertheless, sublethal stress caused by low levels of electricity may result in profound physiological disturbances (Roach 1999;Dwyer et al 2001;Cho et al 2002;Schreer et al 2004).…”

Population structure, individual movement, and growth rate of shortjaw kokopu (Galaxias postvectis) in two North Island, New Zealand streams

“…Haemorrhages in soft tissues and fractures in bone also occur (Reynolds 1996). Recovery from electric fishing-induced injuries generally occurs, however long-term reductions in fitness and growth have been found as a result of electric fishing (e.g., Gatz et al 1986;Dwyer et al 2001;Holliman & Reynolds 2002). In a long-term study of growth and survival it is desirable to avoid sampling-induced mortality and reduction in growth.…”

Density‐ and species‐dependent errors in single‐pass timed electrofishing assessment of riverine salmonids

“…When the aim of the data collection is to determine river or catchment scale fish density estimates, then rapid assessment electrofishing techniques are frequently more appropriate than more quantitatively robust multiple pass techniques (Crozier & Kennedy, ). An additional advantage of rapid assessment electrofishing techniques is the reduced exposure of fish to electrical discharge from electrofishing which can cause injury and stress (Densmore & Panek, ; Holliman & Reynolds, ; Snyder, ).…”