7379

• UCREFRP Catalog Number: 7379
• Author: Tyus, H. M.
• Title: Potamodromy and Reproduction of Colorado Squawfish in the Green River Basin, Colorado and Utah
• USFW Year: 1990
• USFW - Doc Type: Transactions of the American Fisheries Society
• Copyright Material: YES

1038

riety of habitats and often moved locally within
or between eddies, runs, and backwaters. In early
spring, most fish were captured in run and eddy
habitats. However, during high runoffs in spring
and early summer, fish were most often tracked
to backwaters and flooded bottomlands. In low-
water years, fish primarily used backwater habi-
tats, but in high-water years, all radio-tagged fish
used flooded bottomlands. Visual observations in
shallow water ( < 1 m depth) indicated that adults
used sheltered microhabitats, including eddies be-
hind boulders and main-channel runs below sand
bars. During the summer, fish were most often
located in deeper (> 1 m) shoreline habitats, where
signals indicated local movements within the main
channel run-eddy interface and between run and
eddy habitats.

TYUS

Spawning migrations of radio-tagged fish were
associated with spring flows and average river
temperatures of about 140C (Figure 2). Colorado
squawfish began migrations May 27-June 13 in
the Yampa River, and May 23-June 22 in the
Green River (Table I). The midpoint of the
spawning migration for all years combined was
June 15 for the Yampa River (N = 19 fish), and
June 21 for the Green River (N = 29 fish). These
dates coincided with longest days of the year
(summer solstice).
River flows and water temperatures varied an-
nually within and between migratory periods, but
spawning migrations were generally earlier in low-
water years and later in high-water years. The
length of time between the dates of peak spring
flow and the beginning of spawning migration each

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FIGURE 2.-Average annual migration periods of radio-tagged Colorado squawfish superimposed on recorded
discharges (Q, solid line) and temperatures (T, dashed line) in the Green and Yampa rivers. Vertical solid lines
indicate average dates when the first and last fish migrated to spawning areas. Vertical dashed lines are the grand
means fOT these dates.

1.

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