Laserfiche WebLink
<br />injuries (Kocovsky et al. 1997). Colorado pikeminnow live over 12 years (Hawkins <br />1991) and their populations are shocked annually. In this study, the rate of congenital <br />and chronic injuries in Colorado pikeminnow was relatively low and similar to the upper <br />range of background (congenital) abnormalities observed in wild salmonids (0-16%; Gill <br />and Fisk 1966; Hollender and Carline 1994; Sharber and Carothers 1998). <br />This study lacked an unshocked reference group of fish necessary to confidently <br />distinguish acute injuries from injuries of previous origin. In an attempt to collect a <br />reference group of unshocked fish, other studies have used alternative capture <br />techniques such as angling or netting in areas never electrofished (Hollender and <br />earline 1994; Thompson et al. 1997). An unshocked reference group from the wild was <br />not considered reliable because most reaches in the upper Colorado River Basin have <br />been electrofished annually for over 15 years and it is likely that some portion of the <br />Colorado pikeminnow population is electrofished without being captured. An alternative <br />would be to x-ray a group of fish before and after exposure to electrofishing. <br />Unshocked hatchery fish may provide the best source for control fish or use in before <br />and after treatment studies. <br />All Colorado pikeminnow, including those with acute compressions, actively <br />swam away at release suggesting that vertebral compressions did not affect mobility. <br />There was also evidence that even severe vertebral injuries did not result in delayed <br />mortality as evidenced by the recapture of the one fish with both severe external injuries <br />(bruises, punctures, and muscle compaction) and the most numerous (11) vertebral <br />compressions. Growth of this acutely injured fish was less than the average growth of <br />uninjured fish, although it was within the range observed for uninjured fish; however, <br /> <br />14 <br />