7603

• UCREFRP Catalog Number: 7603
• Author: Nesler, T. P.
• Title: Endangered Fishes Investigations
• USFW Year: 1991.
• USFW - Doc Type: Federal Aid Project #SE-3 - Job Progress Report.
• Copyright Material: NO

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Scale samples were also collected from all northern pike and smallmouth bass.
During May and June 1990, northern pike collected at Craig or upstream were
processed as above and transported in a live tank equipped with bottled oxygen
and airs tone to E1khead Reservoir, located north of state highway 40 midway
between Craig and Hayden, Colorado (Figure 1). These pike were acclimated to
reservoir water temperatures for 20-30 minutes and released in the reservoir.
Northern pike and smallmouth bass collected downstream of Craig were analyzed
for stomach content samples, and evaluation of sex and spawning stage. A
pectoral spine for age-growth estimation and stomach sample for food habit
data were taken from all channel catfish collected. Sex and spawning stage
were also evaluated for all channel catfish collected. Colorado squawfish
captured were also measured for length and weight, existing Carlin tag numbers
noted, and scale samples collected for age-growth analyses under Job 8. All
Colorado squawfish were then released in the river at the capture site.
Nongame fish species collected were enumerated by species and also released.
Other data collected at sampling sites included date, time, river mile
location, habitat type sampled, location and presence of adjoining habitat
types, water temperatures in habitat sampled and main channel, and presence of
submersed cover or aquatic vegetation.

Stomach contents of all gamefish were analyzed for the presence of ingested
fish prey. Gamefish stomach contents were removed, preserved in 10% formalin,
and labeled with location and date. Ingested fish were identified to species
when possible, counted, and measured for total length. Total length was
estimated from fish remains if the head and body of the prey was intact.
Other food items were noted when present, and identified by major taxa (Family
or Order).

Seining with various small-mesh seines (3-6 mm) was used in available
shallows and aquatic vegetation throughout the sample season in all river
reaches to determine the presence of young-of-the-year (YOY) gamefish.
Angling was used as a supplementary capture technique during seasons when use
of the electrofishing boat was limited, when effectiveness of electrofishing
or netting due to the habitat type was limited, or while sampling with passive
nets in pools in late summer and early fall.

Colorado River

Sampling included week-long trips in April and July 1989, as well as
standardized monitoring seine surveys for Colorado squawfish YOY in September.
This sampling covered RK 298-225 (Figure 1). Sampling was conducted in April
and June using the block and shock technique described for the Yampa River
above. All centrarchids collected were measured and weighed, and analyzed for
stomach samples and sex determination; scales were collected for age-growth
estimation. All ictalurids were measured and weighed; a pectoral spine taken
for age-growth data; and a representative number of specimens sacrificed,
based on length categories, for stomach samples and sex determination.
Stomach contents of all gamefish collected in April and July were analyzed in
the same manner described for Yampa River fishes.

Sampling in September was accomplished using a 1.2 x 4.6 m beach seine with
3.2 mm ace mesh. The 72 km reach was stratified into 8 km segments within