7959

• UCREFRP Catalog Number: 7959
• Author: Muth, R. T. and J. B. Ruppert.
• Title: Effects of Two Electrofishing Currents on Captive Ripe Razorback Sucker and Subsequent Egg Hatching Success - Final Report.
• USFW Year: 1995.
• USFW - Doc Type: ‎(CO River Recovery Program Project No. 61 RMD/9595)‎,
• Copyright Material: NO

boat-mounted Coffelt WP-15 electrofisher (square waveform, 40 Hz, 20% duty
cycle, 120-V and 8-A output).

Other researchers have investigated effects of electroshocking ripe male and
female fish and found substantial reductions in viability of fertilized eggs through the
eyed stage. Newman and Stone (1992) exposed ripe walleye Stizostedion vitreum
to 400-V, 120-Hz pulsed DC (quarter-sine waveform) and, although no supportive
data were given, suggested that reduced egg viability was possibly caused by
rupture of unfertilized eggs or decreased sperm motility. Marriott (1973) suspected
that overall lower egg viability for pink salmon Oncorhynchus gorbuscha shocked
with 110-V, 60-Hz AC for 5 s was at least partly caused by observed damage to
internal organs of some females which loosened unfertilized eggs from ovarian
tissue and bathed them in body fluids. He concluded that shocking had no effect on
males. We did not observe injuries to internal organs of shocked female razorback
sucker or obvious, treatment-related damage to their eggs but cannot rule out the
possibility of undetected damage to eggs or decreased motility in sperm of shocked
males. Although mean percent hatch of eggs in our control was relatively low
(25.9%), it falls within the reported range of 22.5-54.7% for artificially fertilized eggs
of razorback sucker in hatcheries (Inslee 1982; Hamman 1985) and was
15.3-21.0% higher than means for eggs in shocked groups.

Our results suggest that electrofishing of razorback sucker spawning
aggregations could injure adults, cause premature expulsion of gametes from fish
during exposure to electric fields, and significantly reduce egg hatching success.
Effects of electrofishing on natural reproductive behavior of razorback sucker are
unknown. Given the precarious status of this species, we recommend that the need
for electrofishing over active razorback sucker spawning areas should be carefully
evaluated.

References

Cowdell, B. R, and R A. Valdez. 1994. Effects of pulsed DC electroshock on adult
roundtail chub from the Colorado River in Colorado. North American Journal
of Fisheries Management 14:659-660.

Dwyer, W. P., and R G. White. 1995. Influence of electroshock on short-term
growth of adult rainbow trout and juvenile Arctic grayling and cutthroat trout.
North American Journal of Fisheries Management 15:148-151.

Fredenburg, W. A. 1992. Evaluation of electrofishing-induced spinal injuries
resulting from field electrofishing surveys in Montana. Final report. Montana
Department of Fish, Wildlife, and Parks, Helena.

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