9432

• UCREFRP Catalog Number: 9432
• Author: Modde, T. and M. Fuller.
• Title: Feasibility of Channel Catfish Reduction in the Lower Yampa River.
• USFW Year: 2002.
• USFW - Doc Type: Vernal.
• Copyright Material: NO

native fish.

Removal Feasibility

In 1998, all gear types captured 1,343 catfish weighing 342.5 kg. In 1999, a total of 2,766

channel catfish weighing 729.4 kg were removed in five angling passes through the study area. An

additional 147 catfish were removed in 1999 with electro fishing gear in an unrelated study. No

differences were observed in the catch rates of the last removal pass between control and treatment

reaches in 1998 (t= -0.82, df=3, P=0.470), whereas significant differences occurred between

channel catfish catch rates in treatment and control reaches in 1999 (t= -5.94, df=3, P=0.009)
(Table 5).

Based on the presence of detectable slopes, estimates of population size was possible in

three of four reaches (figure 3). Estimates for treatment reaches 2, 3, and 4, were 718 (SE =134),

1,153 (SE = 1,195), 710 (SE=88) respectively. These estimates represent densities of 101.1

fish/km, 180.2 fish/km, and 87.7 fish/Ian respectively for treatment reaches 2, 3 and 4. Based on

known number offish removed, the estimated removal efficiency was 70.3%, 57.4%, and 81.5% in

reaches 2, 3, and 4 respectively. The assumptions ofthe model used are that all fish in the

population/reach were equally vulnerable to removal through all removal efforts. In addition, we

assumed that fish did not move among reaches. Some bias due to angler access was surely evident

and therefore the assumption of equal vulnerability was certainly not met, and population estimates

may underestimate real abundance. Thus, the population estimates should be interpreted as rough

estimates.

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