9694

• UCREFRP Catalog Number: 9694
• Author: Hawkins, J., C. Walford, and A. Hill
• Title: Smallmouth bass control in the middle Yampa River, 2003-2007.
• USFW Year: 2009
• USFW - Doc Type: Contribution 154 Larval Fish Laboratory, Colorado State University.
• Copyright Material: NO

to eight times and time at large spanned one day to 4 years after their release.

Movement of smallmouth bass between the control and treatment reaches of Little
Yampa Canyon in 2004 and 2005 reduced our ability to compare results from the two
reaches. In 2004, 15% of the tagged smallmouth bass left the treatment reach and 8%
left the control reach. In 2005, 9% of the tagged small mouth bass left the treatment
reach and 24% left the control reach (Table 10). On average, fish moved 11.1 miles
with a range from 0.7 to 50.5 miles. These emigration rates were considered high
enough to negate the control and treatment approach and starting in 2006 the control
reach was eliminated and the treatment reach was expanded to cover the entire 24-mile
Little Yampa Canyon study site. For consistency with later years (2006 and 2007), we
combined mark-recapture data from control and treatment reaches in 2004 and 2005
and estimated abundance for the 24-mile study site.

Movement of recaptured smallmouth bass based on the distance they moved from the
first to the last capture occasion for all years combined showed that 10% remained
stationary and were recaptured in the same V2 mile section of their release. A fairly high
proportion of fish remained within .:t 5 miles of their release location, including 31 % of
bass recaptured less than a year later and 22% of bass recaptured more than a year
after release. Range of movement was farther after longer time at large. Smallmouth
bass at large less than a year were recaptured up to 38 miles downstream and 51 miles
upstream of their release location; bass at large more than a year were recaptured up
to 99 miles downstream and up to 95 miles upstream of their release location (Figure
7). For bass recaptured within a year of initial tagging (n=735), 46% were recaptured
downstream and 41 % were recaptured upstream of their release location (Figure 7).
Movement direction of smallmouth bass at large more than 1 year (n=637) was similar
with 45% and 48% of fish recaptured downstream or upstream, respectively (Figure 7).

Of the smallmouth bass recaptured after release in Little Yampa Canyon, most
remained there and were recaptured in Little Yampa Canyon, including 93% of 581

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