9524

• UCREFRP Catalog Number: 9524
• Author: Kitcheyan, C. D. and e. al.
• Title: Evaluation of the Effects of Stage Fluctuations on Overwinter Survival and Movement of Young Colorado Pikeminnow in the Green River, Utah, 1999-2002.
• USFW Year: 2004.
• USFW - Doc Type: Denver.
• Copyright Material: NO

mortality. Among the three winter periods, the 1999-2000 winter was the mildest(i.e., shortest duration),
and no overwinter size-selective mortality was observed. The 2000-2001 winter was intermediate in
severity, and overwinter mortality occurred, but it was not strong. The 2001-2002 winter had the greatest
severity and the greatest size-selective mortality. Others have also reported size-selective overwinter
mortality for young Colorado pikeminnow (Converse et al. 1997, McAda and Ryel 1999, Thompson et al.
1991). Higher survival of large fish was presumably the result of more fat reserves (Thompson et al.
1991, Beyers and Plampin 2004), and size at the end of the growing season was probably the result of
early arrival date in the nursery habitat (i.e., early hatching date resulting in longer growing season) and
warm summer water temperatures (Bestgen et al. 1997), but habitat availability and food abundance may
also have been important (Tyus and Haines 1991).
Winter Movements
Young Colorado pikeminnow moved only short distances both within autumn and spring
sampling and between autumn and spring sampling. Within autumn and spring sampling, 95% of the
recaptured young Colorado pikeminnow were within the same 5-mile section where they were originally
marked. Of the recaptured fish for which we could determine the backwater of origin, 68% were
recaptured in the backwater of origin, 94% were recaptured within 0.6 mile of the backwater of origin,
and all were captured within 3 miles of the backwater of origin. These fish were at large between 5 and
42 d.
Overwinter movement (between autumn and spring sampling) was about 3 miles or less. Of 14
fish that were marked in the autumn and recaptured the following spring, 13 were recaptured in the same
backwater and one fish was recaptured upstream 3 miles. We point out, however, that most of the fish we
captured were caught in the downstream portion of the 40-mile study reach, and therefore we only
sampled approximately 3 to 6 miles downstream from most marked fish, possibly underestimating the
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