9716

• UCREFRP Catalog Number: 9716
• Author: Stone, D., and P. Sponholtz.
• Title: Translocation of young-of-year humpback chub above Chute Falls in the Little Colorado River, AZ, 2003 Interim Report.
• USFW Year: 2003.
• USFW - Doc Type: U.S. Fish and Wildlife Service
• Copyright Material: NO

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Figure 7. Length frequency histogram of humpback chub collected in the Little Colorado
River during the July 2003 translocation trip and both tagged and untagged individuals
captured during the November 2003 monitoring trip.
Translocated humpback chub (i.e., those with visible elastomer tags) showed significant
growth above Chute Falls (t=22.907; df=334, 2-tailed P=0.000). The largest (134 mm)
individual recaptured that had a clear elastomer tag had grown a minimum of 0.37 mm/day
since its release. This is atypically high growth compared to their 0.29 mm/day average
growth rate found in the lower LCR (Robinson and Childs 2001) or their 0.28 mm/day
average growth in a 24°C hatchery environment (Gorman and Van Hoosen 2000). Even if
that fish was an anomaly, the 0.13-0.67 mm/day range of growth of the median (112 mm)
tagged individual certainly suggests a high growth rate for half of these fish.
The origin of the nine humpback chub without visible elastomer tags is perplexing. If the
155 mm fish were a translocated individual, then it would have to grow 0.60 to 1.14 mm/day
since its release. This is 2 to 4 times the predicted growth rate of Gorman and Van
Hoosen (2000) and Robinson and Childs (2001). Likewise, the 141 mm and 144 mm
"unmarked" individuals would also have undergone high growth. If these were translocated
individuals and their growth rate continued, then they could potentially grow past 200 mm
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