9449

• UCREFRP Catalog Number: 9449
• Author: Hawkins, J. A.
• Title: Recapture and growth rates of three Colorado River endangered fish species
• USFW Year: 2003.
• USFW - Doc Type: a comparison between electrofishing and non-electrofishing.
• Copyright Material: NO

for all three species and ranged 1.2% to 2.7%, although for Colorado pikeminnow the
difference (2.4%) was statistically different at the 95% significance level (P=0.04). Of
the three species, humpback chub had the lowest recapture rates.
Mean growth rates were similar for each of the three species and treatments
regardless of initial sampling gear type (Table 3). Mean growth rates of Colorado
pikeminnow and humpback chub after capture by electrofishing were sightly higher
(differences ranged 0.02-1.28 mm/month) than growth rate after capture by
non-electrofishing gears. The ANCOVA analysis did not detect significant differences
in growth rates of Colorado pikeminnow in the first or second growing seasons after
initial capture (Tables 3, 4, and 5; Figure 1). For humpback chub recaptured during the
first growing season, ANCOVA analysis revealed that regression-line slopes were
significantly different (P=0.05), thus precluding the second ANCOVA test for detecting
different growth rates (Tables 5 and 6; Figure 2); however, simple-mean growth rates
were similar between gear types (Table 3) and not statistically different. For humpback
chub recaptured within the second growth season, ANCOVA analyses detected no
difference in growth rates between gear types (Tables 5 and 6; Figure 2).
Mean growth rates of razorback sucker were also similar for each treatment
regardless of sampling gear type at initial capture. Differences in growth rate ranged
from 0.03-2.1 mm/month for razorback sucker and although growth rate was slightly
less for electrofishing caught fish, the difference was small and not statistically
significant. Razorback sucker recaptured within the first growth season after initial
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