6008

• UCREFRP Catalog Number: 6008
• Author: Archer, D. L., H. M. Tyus, L. R. Kaeding, C. W. McAda and B. D. Burdick.
• Title: Colorado River Fishes Monitoring Project
• USFW Year: 1984.
• USFW - Doc Type: Second Annual Project.
• Copyright Material: NO

Colorado River
Colorado squawfish-Twenty-two Colorado squawfish were implanted with
radio transmitters in 1982 and 21 fish were implanted in 1983 (Tables 3
and 4). Only one radiotagged fish (No. 2) moved among adjacent river
reaches (Figure 7). The pattern of movement exhibited by some fish
within reaches were similar between years. Fish from the upper reach
(RM 125-200) were radiotagged and released in upstream or mid reach (RM
0-100) areas during May and June 1982; one of these fish (No. 20) moved
upstream after its release and then moved rapidly downstream to the
Black Rocks area by mid summer, whereas others (No. 8 and 9) moved to
the Black Rocks area with no apparent prior upstream movement. The
remainder of the radiotagged fish in this river reach exhibited a
variety of up-and downstream movements. Ihtring 1983, some Colorado
squawfish (No. 26 and 28) that had been implanted with long-term radio
transmitters in the Black Rocks area during fall 1982 had moved upstream
to the Grand Junction area by May, and one fish (No. 26) was in the
Palisade area in August. The apparent seasonal nature of these reciprocal
displacements of radiotagged fish suggests that some movement of adult
Colorado squawfish may be related to spawning, and that this movement
might occur between the Black Rocks region and areas upstream, These
data also suggest that fish captu red and implanted with radio transmitters
in May and June 1982 might already have moved upstream from the locations
that the fish occupied during winter. The rapid downstream movement of
some radiotagged Colorado squawfish to the Black Rocks area from the
upper reach during July and August 1982 might have been a movement
toward spawning areas, rather than a post-spawning displacement. The
relative abundance of Larval Colorado squawfish collected from the Black
Rocks area was high within mid-August samples (Miller et a1. 1983) which
would support the hypothesis that a spawning area exists near Black
Rocks. Legget (1977), in a review of the literatu re on fish migrations,
reported that much of the available information suggests that the
movements of fishes "involve a continuous optimization of physiological
and neurological states in response to a multiplicity of environmental
stimuli." The most upstream areas of the upper river reach may not
contain good spawning habitat for Colorado squawfish; radiotagged -fish
might have rapidly left this area as spawning approached in response to
some "environmental stimuli". Relatively few larval Colorado squawfish
were collected from the upstream area of the upper river reach in 1982
(Figure 8), even though many mate re-size Colorado squawfish had been
collected from this area in July (Miller et al. 1983). Thus, radio-
tagged fish which left this area could have moved to better spawning
areas, perhaps near Black Rocks.
With the exception of one fish (No. 2), relatively Little movement was
evident for radiotagged fish in the most downstream Colorado river
reach -- the upper region of Lake Powell. Downstream displacement of
six radiotagged fish (No. 1-4 in 1982 and 38 and 43 in 1983) occurred
after they were released; five of these fish returned to near the
location of their release within 2 or 3 months, whereas no upstream
movement was noted in the sixth fish (No. 3) before radio contact was
lost.
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