9555

• UCREFRP Catalog Number: 9555
• Author: Bestgen, K. R., C. D. Walford, A. A. Hill and J. A. Hawkins.
• Title: Native Fish Response to Removal of Non-native Predator Fish in the Yampa River, Colorado.
• USFW Year: 2007.
• USFW - Doc Type: 140,
• Copyright Material: NO

smallmouth bass from 1999 to 2001, and the decline in native fish in the
be related.
Other elements of the non-native fish community also changed
In 1981-1982, redside shiners comprised about 50% of fish captured in all sar
minnows an additional 10-20%. Sand shiners were relatively rare, at 5% or le
community. In 2003-2006, redside shiners were rare (0.3%) and sand shiners
most abundant species (28.6%); fathead minnow remained relatively commo
period, may also
i the two periods.
pies, and fathead
;s of the fish
were the second-
(7%). Shifts in
species composition of shiners may be related to shifts in water temperatures, which were
warmer in the study area in the 2003-2006 period than historically occurred. eside shiners are
generally a more cool-water tolerant species occurring upstream in higher ati
shiners are more common in downstream reaches with warmer water. Warn
years may be responsible for declines in redside shiner and increased abund~
Anderson (2002) also noted reduced abundance of redside shiner and increa;
sand shiner in samples collected in 1999 and 2001 in the same area. This up
abundance pattern shift is repeated in the Green River where redside shiners
in cooler upstream reaches of Browns Park and upper Lodore Canyon and s~
abundant in the warmer reaches of lower Lodore Canyon and Whirlpool Cai
Crist 2000; Bestgen et al. 2006b).
e and sand
water m recent
of sand shiner.
abundance of
am-downstream
re more abundant
shiner is more
i (Bestgen and
Yampa River fishes, control-treatment reach comparisons.-In the fir t two years of
smallmouth bass removals, 2003 and 2004, a relatively small proportion of b ss were removed,
and all fish removed were age-1 or older (Hawkins 2005, 2006). For exampl , in 2003
smallmouth bass were removed on only one of six electrofishing passes, with a total of 294 bass
removed, or about 11 % of the estimated population (estimated abundance of bout 2500 fish >
150 mm TL). In 2004, abundance of smallmouth bass > 150 mm TL in the tr atment reach of
the study area was estimated at 1,325 (CV = 30%); 1600 smallmouth bass of 11 sizes were
handled in the treatment reach in 2004 and 919 of those were > 150 mm TL a d were removed.
Thus, the 2004 removal rate was about 69% for that size group.
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