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<br />lJ6
<br />
<br />BARRElT AND GROSSMAN
<br />
<br />though we were only able to statistically evaluate
<br />data for mottled sculpin. It seems possible, how-
<br />ever, that species-specific or situation-specific
<br />responses to electrofishing could exist. Conse-
<br />quently, researchers concerned about electrofish-
<br />ing-induced mortality should test the response of
<br />their experimental animals before using this tech-
<br />nique. Our results indicate that electrofishing in
<br />low-conductivity Appalachian streams probably
<br />wiD not cause significant short-term mortality
<br />among mottled sculpin. Min~ization of handling
<br />stress is more likely to eliminate collection-related
<br />mortality than would a switch to alternative, non-
<br />electrical modes of collection.
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<br />Acknowledgments
<br />
<br />We thank the staff of the Southeastern Forest
<br />Experiment Station, Coweeta Hydrologic Labo-
<br />ratory, for their help with the fieldwork. We are
<br />grateful to Lori Hayek for her patience in the field,
<br />and to Lori Hayek and Barbara Mullen;for their
<br />support while this manuscript was being prepared.
<br />We thank Maurice Crawford, Doug Facey, Margi
<br />Hood, Mary Freeman, Jerry Freilich, Beth Gol-
<br />dowitz, Stan Hales, lennifer Hili, Deanna Stouder,
<br />Tim Welch, ,and three anonymous reviewers for
<br />their contributions to this research, Financial sup-
<br />port for this project was provided by a grant from
<br />the U.S. Forest Service McIntire-Stennis program
<br />(GEO-OO35-MS) to the junior author and by the
<br />School of Forest Resources, University of Georgia.
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<br />References
<br />
<br />Bouck, G, R., M, A. Cairns, and A. R. Christian, 1978.
<br />Effect of capture stress on plasma enzyme acti vi ties
<br />in rainbow trout (Salmo gairdneri), Journal of the
<br />Fisheries Research Board of Canada 35: 1485-1488.
<br />Bums, T. A., and K. Lantz. 1978. Physiological effects
<br />of electrofishing on largemouth bass, Progressive
<br />Fish-Culturist 40: 148-150.
<br />Gatz, J, A., J, M, Loar, and G, F. Cada. 1986, Effects
<br />of repeated electroshocking on instantaneous growth
<br />oftrout. Nonh American Journal of Fisheries Man-
<br />agement 6:176-182.
<br />Hauck, R. F. 1949. Some harmful effects of the electric
<br />
<br />:J
<br />~,
<br />.
<br />~'
<br />.
<br />~
<br />~
<br />
<br />shocker on large rainbow trout. Transactions of the
<br />American Fisheries Society 77:61-64,
<br />Hill, J., and G. D, Grossman. 1987. Effects ofsubcu-
<br />taneous marking on stream fishes. Copeia 1987 :492-
<br />495.
<br />Horak, D, L" and W, D, Klein, 1967. Influence of
<br />capture methods on fishing success, stamina, and
<br />monality of rain bow trout (Salmo gairdnen) in Col-
<br />orado, Transactions of the American Fisheries So-
<br />ciety 96:220-222.
<br />Hudy, M, 1985, Rainbow trout and brook trout mor-
<br />tality from high voltage AC electrofishing in a con-
<br />trolled environment. Nonh American Journal of
<br />Fisheries Management 5:475-479.
<br />Kynard, B., and E. Lonsdale, 1975, Experimental study
<br />of galvanonarcosis for rainbow trout (Salmo gaird-
<br />ner/) immobilization, Journal of the Fisheries Re-
<br />search Board of Canada 32:300-302,
<br />Lamarque, p, 1967, Electrophysiology of fish subject
<br />to the action of an electric field, Pages 65-92 in R.
<br />Viben, editor. Fishing with electricity: its applica-
<br />tion to biology and management. Fishing News
<br />Books, London.
<br />Pickering, A. D" T, G, POllinger, and p, Christie, 1982,
<br />Recoy}'iy of the brown trout, Salmo trulla L, from
<br />acute handling stress: a time-course study, Journal
<br />of Fish Biology 20:229-244.
<br />Pratt, V, S, 1954, Fish monality caused by electrical
<br />shockers, Transactions of the American Fisheries
<br />Society 84:93-96.
<br />Reynolds, J, 1983, Electrofishing, Pages 147-163 in L.
<br />A, Nielsen and D. L. Johnson, editors. Fisheries
<br />techniques. American Fisheries Society, Bethesda,
<br />Maryland,
<br />Schreck, C. B., R. A Whaley, M, L. Bass, O. E. Maughan,
<br />and M. Solazzi. 1976, Physiological responses of
<br />rainbow trout (Salmo gairdnen) to electroshock,
<br />Journal of the Fisheries Research Board of Canada
<br />33:76-84,
<br />Spencer, S, L. 1967, Internal injuries of largemouth
<br />bass and bluegills caused by electricity, Progressive
<br />Fish-CuIturist 29: 168-169.
<br />Wedemeyer, G, 1972. Some physiological conse-
<br />quences of handling stress in the juvenile coho salm-
<br />on (Oncorhynchus kisutch) and steelhead trout (Sal-
<br />mo gairdnen). Journal of the Fisheries Research
<br />Board of Canada 29: 1780-1783.
<br />Whaley, R, A" 0, E. Maughan, and P. H. Wiley, 1978.
<br />Lethality of electroshock to two freshwater fishes.
<br />Progressive Fish-Culturist40:161-163,
<br />
<br />North American Journal of Fisheries MarJagemE'11f 8:111-122,1988
<br />@ Copyright by the American Fisheries Society 1988
<br />
<br />Influence of Electrofishing Pulse Shape on Spinal
<br />injuries in Aduit Rainbow Trout
<br />
<br />N. G. SHARBER AND S. W. CAROTHERS
<br />
<br />lchthyo Technologies, Post Office Box 96
<br />Flagstaff, Arizona 86002, USA
<br />
<br />Abstract. -Adult rainbow trout Salmo gairdneh captured by electrofishing were analyzed for
<br />spinal injury by X-ray photography and autopsies, The effects of three electrical pulse shapes were
<br />compared, Of 209 fish captured, 50% suffered spinal injuries involving an average of eight venebrae
<br />that were dislocated, splintered, or both, One-quaner-sine wave pulses injured a significantly higher
<br />proponion of fish (67%) than either exponential pulses (44%) or square wave pulses (44%; P <
<br />0,05). Quaner-sine waves also damaged significantly more venebrae per fish (average, 9.5) than
<br />did exponential pulses (6.6); the average number damaged by square waves (8,2) did not differ
<br />significantly from either of the other means, Electrofishing could bias mark-recapture studies of
<br />large rainbow trout. Electrofishing in waters containing endangered or threatened species should
<br />be considered v.~th great caution.
<br />
<br />Electrofishing is a widely used research and
<br />management technique that can result in injury to
<br />fish. The rate and seriousness of injury varies
<br />markedly within and among species (Hauck 1949;
<br />Collins et al. 1954; Godfrey 1954; Pratt 1954;
<br />McCrimmon and Bidgood 1965; Horak and Klein
<br />1967; Spencer 1967; Vibert 1967a; Maxfield et al.
<br />1971; Hudy 1985).
<br />Many factors can influence the frequency and
<br />extent of electro fishing-induced injury. Environ-
<br />mental conditions (e,g., conductivity of water,
<br />depth of water, or substrate) affect electrofishing
<br />efficacy, as do the type of electrical hardware and
<br />amount of electrical current used (Sternin et al.
<br />1972). Even in the most controlled laboratory sit-
<br />uations, so many variables affect the amount of
<br />electrical current passing through the body of a
<br />fish that the head-to-tail electrical potential is im-
<br />possible to predict (Lamarque 1967; Schreck et al.
<br />1976). For example, large fish are subjected to
<br />higher voltage gradients than small fish (Ellis 1975),
<br />and density of the electric current near the elec-
<br />trodes is directly related to the electrode's size,
<br />\ shape, and electrical resistivity (Novotny and Prie-
<br />I gel 1974). Lamarque (1967) reported that the shape
<br />of the electrical pulse influences the rate and extent
<br />of injury to fish.
<br />For the commonly used DC electrofishing de-
<br />vices, three pulse shapes are available: exponen-
<br />tial, square wave, and one-quarter-sine wave (Has-
<br />kell 1954; Halsband 1967; Hartley 1967). The
<br />exponential pulse is the most effective and least
<br />traumatic (Halsband 1967; Hartley 1967; Sternin
<br />et al. 1972; Novotny and Priegel 1974), Steroin et
<br />al. (1972) demonstrated the relative rates of in-
<br />
<br />duced trauma using these pulse shapes in labo-
<br />ratory experiments; however, we know of no field
<br />experiments that demonstrate varying levels of
<br />trauma as a function of pulse shape. Our objective
<br />was to determine the frequency of spinal-column
<br />injuries to adult rainbow trout Salmo gairdneri
<br />immobilized in the field by electrofishing with dif-
<br />ferent pulse shapes.
<br />
<br />Methods
<br />
<br />Study design, - The study was conducted on the
<br />Colorado River in Glen Canyon National Recre-
<br />ation Area and Grand Canyon National Park, Co-
<br />conino County, Arizona, Electrofishing was a prin-
<br />cipal means of capturing fish during five sampling
<br />trips in 1985 and 1986. Water temperature ranged
<br />from 9 to IIOC, and conductivity from 600 to 800
<br />ItS/cm. Water depth at sample locations ranged
<br />from I to 3 m. Rainbow trout used in our analyses
<br />had a mean total length of 360 mm (SE, 52.9;
<br />range, 300-560 mm).
<br />We collected specimens at random over_a 108,5-
<br />km stretch of river (Glen Canyon Dam to Nan-
<br />koweap Canyon). The 209 fish examined were di-
<br />vided into three experimental groups based on the
<br />pulse shape used to capture them (exponential,
<br />N '" 99; square, N = 55; one-quarter-sine, N =
<br />55). Throughout the sample area we alternated the
<br />pulse shapes used, fishing for approximately I h
<br />at a time with each pulse. It was not possible for
<br />us to select a specific capture locality. Due to the
<br />logistical difficulties in traveling on the Colorado
<br />River in the Grand Canyon, our exact location
<br />each night was impossible to preselect, Ten to 30
<br />fish were taken at random from the live well after
<br />
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