Glenn Parsons, University of Mississippi
([log in to unmask]), inquired:
>I have a question that is related to the discussion of electrofishsing. We
>use electroshocked crappie (Pomoxis annularis and P. nigromaculatus) for
>strip spawning in my lab. Is anyone aware of any effects of electroshock
>on egg viability, that is, could our problems with successfully strip
>spawning crappie be due to the fact that the female was electroshocked?
The answer is "quite probably", but degree of impact (which in some cases
might be negligible) apparantly varies with species, precise condition of
the fish when shocked (how ripe), the nature and strength of the electrical
field at the point of impact, and subsequent handling. A few years ago I
did an intensive review of the effects of electrofishing on fish for the
Glen Canyon Ecological Studies Aquatic Coordination Team and U.S. Bureau of
Snyder, D. E. 1992. Impacts of electrofishing on fish. Report of
Colorado State University Larval Fish Laboratory to U.S Department of
the Interior Bureau of Reclamation, Salt Lake City, Utah, and Glen
Canyon Environmental Studies Aquatic Coordination Team, Flagstaff,
(Copies on paper or microfiche are available through the Fish and Wildlife
Reference Service, 5430 Grosvenor Lane, Suite 110, Bethesda Maryland,
20814-2158; phone 1-800-582-3421; fax 1-301-563-4059; email
[log in to unmask] MIN 809440039.) The following article
summarizing the reported effects of electrofishing on fish reproduction and
gamete viability was abstracted from that report and published in American
Fisheries Society Early Life History Section Newsletter 14(3):27-29 (1993).
[Incidentally, I urge persons interested in any aspect of the early life
history of fishes to join this section. The newsletter, edited by Tom
Miller of the Chesapeake Biological Laboratory, is excellent and dues for
either AFS members or non-AFS affiliate membership is only $10 per year.]
Effects of Electrofishing on Fish Reproduction, Gametes, and Offspring
Darrel E. Snyder
Larval Fish Laboratory
Colorado State University
Fort Collins, CO 80523
Spawning fish often aggregate in accessible localities and are
sometimes considered more vulnerable to electrofishing than other life
stages (Stewart 1967 as cited by Lamarque 1990; Kolz and Reynolds
1990). For these reasons, studies employing electrofishing sometimes
target the spawning season. Most of our knowledge of effects of
electric fields on fish reproduction, gametes, and subsequent
offspring is based on collection of brood stock, hatchery operations,
and artificially fertilized eggs. The effects of electrofishing on
the natural reproductive behavior of fish exposed while in ripe or
near-ripe condition are unknown.
Halsband (1967) reported that gonads were unharmed by
electrofishing, and Halsband and Halsband (1975, 1984) explicitly
stated that "Harmful genetic effects or harmful effects to the
progeny are also not produced." According to Vibert (1967), "McGrath
reported that . . . no ill effects have been recorded in hatcheries on
the offspring of wild trout caught by electricity." Maxfield et al.
(1971), who subjected young-of-the-year and yearling rainbow trout
(Oncorhynchus mykiss) to 8- and 5-hertz (pulses or cycles per second)
pulsed direct current, respectively, reported that subsequent
fecundity of those fish and mortality of their offspring through eyed-
egg, hatching, and initial feeding stages was not consistently
different from that of unexposed fish. Khakimullin and Parfenova
(1981) reported no ill effects of pulsed 6-hertz, 40-millisecond
alternating current on Siberian sturgeon (Acipenser baeri) spawners or
subsequent (pituitary-induced) gamete maturation and development of
eggs and larvae (if the alternating current was rectified, then the
current was actually a form of pulsed direct current). Similarly
Valdez (pers. commun.) and Pfeifer (pers. commun.) reported no adverse
effects of pulsed-direct-current electrofishing on ripe lake trout
(Salvelinus namaycush) and walleye (Stizostedion vitreum),
respectively, or on the survival of their artificially fertilized
eggs. However, other researchers have observed adverse impacts.
Marriott (1973) compared mortality of artificially fertilized pink
salmon (Oncorhynchus gorbuscha) eggs from unshocked and electrocuted
(110-volt, 60-hertz alternating current) males and females. He found
mortality through a late-eyed stage to be 12% higher for eggs from the
electrocuted females. Two of the electrocuted females had severely
ruptured internal organs and most of their eggs were loose and bathed
in body fluids; this might have accounted for at least some subsequent
egg mortality. Additional exposure of a batch of fertilized eggs from
electrocuted adults to an electric field resulted in 27% greater
mortality than for eggs which were never exposed to an electric field.
Marriott recommended that electrofishing not be used to capture ripe
Newman and Stone (unpubl. ms. 1992) subjected ripe walleye to 120-
hertz pulsed direct current (400 volt, 3 amp, quarter-sine waveform)
and documented the viability of subsequently fertilized eggs. The
fish were held in a net enclosure as an electrofishing boat made two
slow passes about 0.7 m from the net. Mortalities for eggs
artificially fertilized from the exposed fish, 63% to 65%, were
significantly higher than the overall average, 37%, for unshocked
brood stock. The authors also noted that the hatchery manager for the
Lac du Flambeau Tribal Hatchery, L. Waronowicz, who cooperated in
their experiments, had severe viability problems with eggs from
electrofished brown trout (Salmo trutta). He and other hatchery
managers had observed broken eggs when stripping electrofished brown
trout and suspected that the albumen from the eggs might clog the
micropyles in many unfertilized eggs. The authors also noted that
some researchers suspected that electrofishing ripe males might result
in a loss of sperm motility.
Next issue: "Effects of Electrofishing on Fish Embryos, Larvae, and
Halsband, E. 1967. Basic principles of electric fishing. Pages
57-64 in R. Vibert, editor. Fishing with electricity, its
application to biology and management. Fishing News (Books) Ltd.,
Halsband, E., and I. Halsband. 1975. [Electrofishing] Die
Electrofischerei [German]. Heenemann VBH, Berlin.
Halsband, E., and I. Halsband. 1984. Electrofishing [English
translation of Halsband and Halsband 1975 from German by R. W.
McCauley, text only exclusive of reference list]. Canadian
Translation in Fisheries and Aquatic Sciences 5048.
Khakimullin, A. A., and N. A. Parfenova. 1984. Effect of pulse
electric shock on reproductive ability and progeny of Siberian
sturgeon, Acipenser baeri (Acipenseridae). Journal of Ichthyology
(English Translation of Voprosy Ikhtiologii) 24:122-129.
Kolz A. L., and J. B. Reynold. 1990. Principles and techniques of
electrofishing [outline manual for course]. U.S. Fish and Wildlife
Service Fisheries Academy, Office of Technical Fisheries Training,
Kearneysville, West Virginia
Lamarque, P. 1990. Electrophysiology of fish in electric fields.
Pages 4-33 in I. G. Cowx and P. Lamarque, editors. Fishing with
electricity, applications in freshwater fisheries management.
Fishing News Books, Blackwell Scientific Publications, Ltd., Oxford,
Marriott, R. A. 1973. Effects of electric shocking on fertility of
mature pink salmon. Progressive Fish-Culturist 35:191-194.
Maxfield, G. H., R. H. Lander, and K. L. Liscom. 1971. Survival,
growth, and fecundity of hatchery-reared rainbow trout after
exposure to pulsating direct current. Transactions of the American
Fisheries Society 100:546-552.
Newman, L. E., and F. G. Stone. Unpublished manuscript, 1992 draft.
Reduced viability in walleye eggs caused by exposure to pulsed DC
electrofishing. Ashland Fishery Resources Office, U.S. Fish and
Wildlife Service, Ashland, Wisconsin.
Pfeifer, F. K.. Personal Communication. Colorado River Fishery
Project, U.S. Fish and Wildlife Service, Grand Junction, Colorado.
Stewart, L. 1967. An investigation into the effects of electric
fishing equipment on salmon and sea-trout within the area of
Lancashire River Board. Lancashire River Board Report, Lancaster,
England. [This reference was cited by Lamarque (1990) but not
included in the corresponding bibliography; according to Dr. Ian
Cowx, who provided this bibliographic data, the title is the same as
for Stewart's 1962 publication which was included in the
Valdez, R. A.. Personal Communication. Bio/West, Inc., Logan, Utah.
Vibert, R. 1967. General report of the working party on the
applications of electricity to inland fishery biology and
management. Pages 3-51 in R. Vibert, editor. Fishing with
electricity, its application to biology and management. Fishing
News (Books) Ltd., London.
Also see a recent publication by two Larval Fish Laboratory associates.
Muth, R. T., and J. B. Ruppert. 1996. Effects of two electrofishing currents on captive ripe
razorback suckers and subsequent egg-hatching success. North American Journal of
Fisheries Management 16:473 476.
Darrel E. Snyder Research Associate
Larval Fish Laboratory Curator, LFL Collection
33J Wagar Building Telephone: (970)491-5295
Colorado State University Fax: (970)491-5091
Fort Collins, Colorado 80523 E-mail: [log in to unmask]