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I I I I I I I I I I I I I I I I I I I Impacts of Electrofishing on Fish Broader questions are also being re-considered. Biologists are concemed about potential effects of electrofishing injuries on the survival, growth, reproduction, and general well-being of the populations and communities they are studying. They are also concerned about the validity and interpretation of data based on fish collected by electrofishing. Horak and Klein (1967), Spencer (1967), Hudy (1985), and Schneider (1992) reported that electrofishing injuries often heal and are not necessarily lethal or debilitating. Although most fish apparently survive electrofishing-induced spinal injuries, Lamarque (1990) suggested that growth would certainly be impaired. Sharber and Carothers (1988, 1990) noted that we do not know how long fish with electrofishing injuries will survive and suggested that at least for large rainbow trout (the subjects of their investigation) such spinal injuries might bias age, growth, and population studies based on mark-recapture techniques. Sharber and Carothers (1988, 1990) also cautioned that the detrimental impact of such injuries might be very significant for populations of fishes that are already endangered. Why has electrofishing injury with relatively modem equipment not been recognized as a potentially serious problem until now? Probably because most spinal injuries are not externally obvious and can only be detected by X-ray analysis or necropsy. [Necropsy is the dissection and examination of a dead body whereas "autopsy" is specifically the examination of a dead human body. Accordingly, the tenn autopsy is misused in much of the electrofishing literature.] If captured fish appear to recover sufficiently to swim away and there are no notable external injuries, we typically consider the fish "unhanned" and assume they will continue to grow and behave nonnally. Schreck et al. (1976) and Whaley et al. (1978) suggested that even recovery from the physiological stresses of electrofishing and handling seldom requires more than a few hours to a day. Also, we often accept some injury or mortality as an unavoidable by- product of most fish collection techniques. In many sampling situations, electrofishing has been considered the most efficient and least damaging collection technique available. Recognized authorities on electrofishing have emphasized its benign qualities at least when using currents other than AC. Halsband (1967) stated that "the Review 5 hannlessness of electric current to fish and their food organisms has already been proved on several occasions." In the foreword to their book on electrofishing, Stemin et al. (1972, 1976) suggested that the theory and practice of electrical fishing in recent decades have put to rest concerns about deleterious effects on nonnal vital activity and natural reproduction of fish. More emphatically, Halsband and Halsband (1975, 1984) stated that "today we are convinced that electrical collecting, repelling, and stunning methods neither cause pain to animals nor injure them intemally or externally, (apart from unavoidable exceptions)." Even now, some biologists (Nehring 1991; Schneider 1992) maintain that years of electrofishing, even with AC (Schneider 1992), has not had a detrimental effect on the specific populations they manage or monitor. Accordingly, they suggest that the occurrence of electrofishing injuries in their situations is either very low or insignificant. If such injuries do occur in notable numbers but do not significantly affect population size and recruitment, perhaps the concem should be for resource quality. For some fish, spinal injuries result in pennanently bent backs and related defonnities (Figures 2, 3), sometimes not becoming obvious until well after theelectrofishing event. For other fish, spinal injuries might only be revealed by X rays or dissection, possibly on a fishennan's dinner table. "Brand" or "bum" marks are particularly obvious indications of injury (Figure 4). Fishery workers often consider these usually temporary marks to be a result of direct contact with or close proximity to the electrode, but they also occur on fish netted some distance from the electrode (Lamarque 1990). Some of these marks may indeed be bums from contact with the electrode (Lamarque 1990), but most are the result of intensified melanophore pigmentation in the skin stimulated by spinal injuries and related trauma (Emery 1984; Lamarque 1990; Fredenberg 1992) or hemorrhages in or under the skin (Reynolds unpubl. ms. 1992). Even 25 years ago, Horak and Klein (1967) identified the cause of these marks as internal hemorrhages and possible damage to the vertebrae. Although the presence of brands is almost surely an indication of spinal injury, their absence does not indicate lack of spinal injuries (Fred en berg 1992). Injured fish often show no external signs of injury.