8100

• UCREFRP Catalog Number: 8100
• Author: American Fisheries Society.
• Title: Proceedings of the 22nd Annual Meeting, Colorado - Wyoming Chapter, American Fisheries Society.
• USFW Year: 1987.
• USFW - Doc Type: March 11-12, 1987.
• Copyright Material: NO

stocking downstream of Saratoga was discontinued as it was felt that the
abundance of small fi sh from upstream sections woul d suppl ement the downstream
fi sh popul at ions through dri ft. Al though high rates of natural reproduction
could sustain the wild trout fishery, it was concluded that selective fishing
harvest was responsible for altering the size structure of the fishery towards a
larger proportion of smaller size groups. Goals were then established for the
fishery above Saratoga which would serve to protect wild trout and increase
numbers of fish towards larger size groups while maintaining acceptable harvest
and catch rates (McDowell 1983).

To meet these goals, a slot limit regulation was implemented in 1982 that
was des i gned to protect that segment of the trout popul at ion wh i ch represented
the most important spawning population and the most heavily harvested size group
of trout, while at the same time permit a limited harvest of larger trout. This
regulation limits the harvest of trout above the town of Saratoga to 6 trout/day
or in possession, only one of which could exceed 16 inches. All trout between 10
and 16 inches must be released and terminal tackle is restricted to the use of
artificial flies and lures only.

The purpose of this presentation is to report on population data and a study
conducted during 1986 to evaluate the success of this regulation in attaining the
goals set forth for managing this wild trout fishery.

RESULTS

Trout popul at ions were evaluated at three stations. The Treasure Island
station has been the primary location for comparing pre- and post-regulation
effects. The station is approximately 43 miles downstream of the Colorado-
Wyoming state line. Continuous electrofishing data has been collected since 1978
by the Fisheries Population Unit during late summer. The general question to be
answered is how have numbers of trout changed within the size categories of the
slot limit regulation?

a) Based on annual mean numbers of trout per mile, rainbow trout greater
than 9.9 inches have increased 68% and brown trout have increased 86%
since the regulation change began in 1982.

b) Within the slot limit (10-16 inches), rainbow trout have increased 57%
and brown trout have increased 83% based on annual mean numbers of
trout per mile since the regulation change. The vertical line
indicated the year the regulation began.

c) Rainbow and brown trout greater than 16 inches have increased 475% and
120%, respectively since the regulation change.

d) The age structure for rainbow trout has shifted to a larger percentage
of older fish since the slot limit regulation began. Ages 1-5 changed
by -17%, 45%, 97%, 82% and 725%, respectively.

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