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8 INFORMATION AND TECHNOLOGY REPORT--2003-0002 ~.~ Fig. 4. Bent backs and abnonnal growth in west slope cutthroat trout (Oncorhynchus clarki /ewisi) probably caused by electrofishing (top and middle photographs) with normal trout for comparison (bottom photograph). (All about 38- 40 cm TL. Top two fish were the only obviously defonned specimens among 93 trout maintained as broodstock in Kiakho Lake, British Columbia, in June 1991. All fish were originally captured as 1 to 3-year-oldjuveniles a few years earlier by stream electrofishing, and that event was considered the most likely cause for the defonnities. However, such defonnities are sometimes attributed to other causes. Photographs provided by and reproduced with pennission of G. Oliver, Kootenay Region, British Columbia.) recently, Smith-Root, Inc. (I998) offered a special' "sweeping" PDC waveform that progressively decreases duty cycle from 60 to 10% during the first 10 s each time the control unit is switched on by reducing either pulse width or frequency. The manufacturer suggested that this new waveform will minimize injury by reducing the percentage of time that electricity is applied as fish are attracted from cover to the anode. Even theories regarding the causes and mechanisms offish responses in electric fields are being reexamined in an attempt to identify and explain specific factors associated with injuries. During the workshop on electro fishing injury held in July 1991 as part of the annual meeting of the Western Division of the American Fisheries Society in Bozeman, Montana, N.G. Sharber introduced what has since often been referred to as the "Bozeman paradigm." His theory is that the observed responses of fishes in electric fields, including muscular seizures resulting in spinal and related injuries, represent essentially the same phases of epilepsy observed in