8206

• UCREFRP Catalog Number: 8206
• Author: Miller, W. J. and D. E. Rees.
• Title: Colorado Squawfish habitat use and movement during summer low flow in the Yampa River upstream of Cross Mounatin Canyon. Final Report.
• USFW Year: 1997.
• USFW - Doc Type: Fort Collins, Colorado.
• Copyright Material: NO

Wick et al. (1983) reported migration from the Upper Yampa to the Lower 321an of the Yampa
Canyon during late June and early July. Tyus (1990) reported migrations occurring between late
May and mid June on the Yampa River and late May to late June on the Green River. Miller et al.
(1982) reported migrations between late June to early July. Osmundson and Kaeding (1989)
reported increased movement of Colorado squawfish from late June and early July to late August
on the Colorado River near Grand Junction, Colorado.
Migration to spawning areas roughly coincides with the decrease of spring runoff and an increase in
water temperatures. Tyus (1990) reported migration beginning approximately 28 days (d) after peak
spring flows when mean water temperatures were approximately 14°C. Wick et al. (1983)
observed migration in radio-tagged squawfish after temperatures rose to 16°C. Tyus (1990) noted
the midpoint of migration coincided with the summer solstice and suggested photoperiod may be
important in initiating migration. Tyus (1990) reported spawning migrations occurring earlier in
low water years and later in high water years. Wick et al. (1983) suggested other environmental
factors besides flow may be important in initiating migrations.
Spawning migrations may be an important adaptation to a highly variable environment (M.L. Smith
1981; Tyus 1986). Migration to suitable spawning habitat may have some advantages in widely
fluctuating environmental conditions (Tyus 1986).
Non-Reproductive Movement
Non-migrating behavior in the Yampa River was noted by several authors (Wick et al. 1983; Tyus
and McAda 1984; Tyus 1990). These authors attributed this behavior to sexual immaturity in
Green River sub-basin squawfish. Only half of females (< 503 mm) captured by Seethaler (1978)
were sexually mature in the Yampa River. Tyus and McAda (1984) found one 510 mm TL
immature male. Miller et al. (1983) reported the average size of 4 non-migrants tagged on the
Green, and White rivers was 476.5 mm TL and the average size of 11 migrants was 565 mm. Tyus
(1990) and Hawkins (1991) reported a longitudinal separation between adults and juveniles; non-
migratory behavior in juveniles may maintain this boundary. Tyus (1986) suggested that this
strategy may be an evolutionary adaptation to reduce intraspecific competition and predation.
Although adult Colorado squawfish may migrate long distances, movement within their home
range is relatively limited. In the Yampa River, Wick and Hawkins (1989) found that squawfish
were often active within a particular habitat but rarely moved outside the reach (average of 0.3
miles) selected for overwintering. Valdez and Masslich (1991) also found that Colorado squawfish
generally overwinter in localized Green River regions (3-5 km long).
Habitat Use
During spring runoff, many native and nonnative fish species (including Colorado squawfish and
northern pike) utilize backwater habitats as refuge from high flows (Wick et al. 1983, 1986; Tyus
and McAda 1984; Osmundson and Kaeding 1989; Tyus 1990). Water temperatures are higher in
backwaters and provide better conditions for growth and gonad maturation (Wick et al. 1983,1986;
Osmundson and Kaeding 1989; Tyus 1990). Wick et al. (1983) suggested that the warmer spring
backwaters may influence the spawning time of migrant fish. Osmundson and Kaeding (1989)
Final Report - Colorado squawfish habitat Page 4
Miller Ecological Consultants, Inc. December 17, 1997