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<br />electrofishing because fish were not killed and necropsied. But even necropsy has <br />failed to reveal the cause of death for many Colorado pikeminnow examined by fish- <br />health experts. Vertebral injuries may not be related to other injuries and non-vertebral <br />injuries may be of greater concern to the performance or survival of injured fish. <br />General observations previously discussed of fish killed in other studies or severely <br />injured after electrofishing suggest that injuries may independently or in accumulation <br />with other stressors induce physiological shock resulting in death soon after the capture <br />event. Although injury may increase the potential for physiological shock, other <br />environmental stressors associated with capture and handling may have an equal or <br />larger role in fish survival. Kelsch and Shields (1996) noted that water quality has an <br />important role in fish survival. Poor water quality would include high water <br />temperatures; rapid, extreme temperature changes as fish are transferred from site <br />water to live-well water; or insufficient oxygen content of live-well water that may contain <br />many other fish. All of these are potential characteristics of conditions found in <br />backwater habitats where Colorado pikeminnow have been reported dying after <br />capture. Most of these conditions are controllable by observant field crews but <br />improved handling procedures should be established and taught. <br />For common species, some mortality from electrofishing is acceptable given the <br />benefits obtained from using the technique especially since many studies would be <br />impossible without electrofishing as a capture technique. Schill and Beland (1995) <br />recommended that some level of harm at the individual level was acceptable as long as <br />the harm does not cause population-level effects. For rare species, the same caveat <br />applies but even more care is required because harm to even a few individuals may <br /> <br />17 <br />