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 = 6.7; 95% CI = 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).