Laserfiche WebLink
v c d V v .... .. . v .u .~ ~. 1 a ~ v J Q 1 u F/ 1 c .~ 1 1! L 11 c u !/ ~ V a v u. u .... ~..... .. .... `. ._. `.. __ <br />River because suitable habitat, and thus larval survivorship, is <br />nearly nonexistent. The larvae found far downstream from known <br />spawning areas may be produced nearby- only 35% of radiotagged <br />' Colorado squawfish in the Green River aggregate at known spawning <br />sites (L. Kaeding, USFWS; pers. comm.). <br />Causes for Decline and Limiting Factors <br />Factors that are blamed for reduced numbers of Colorado <br />squawfish include blocked spawning and seasonal migration routes, <br />habitat loss, altered water flow and temperature regimes, and <br />competition with nonnative fish species (USFWS 1984a). Colorado <br />squawfish life strategy may be poorly adapted to controlled riverine <br />environments and to compete with exotic fish species (Tyus 1985b). <br />Dams may be a main cause for decline of the species in the Upper <br />Basin by blocking migrations to spawning areas (Tyus 1984). <br />Extirpation of Colorado squawfish from the Lower Basin coincided <br />with construct-ion of dams, stream dewatering and spread of nonnative <br />fish species (Miller 1961, Minckley and Deacon 1968). <br />Habitat loss due to construction of Colorado River Storage <br />Project-Dams is blamed for Colorado squawfish rarity in the Upper <br />Basin (Holden and Wick 1982, Behnke and Benson 1983). Reservoirs <br />eliminate river habitats and replace them with lacustrine habitats <br />that are unsuitable for reproduction of native fish species (Holden <br />and Stalnaker 1975b, Behnke and Benson 1983). Tailwaters below <br />Upper Basin dams are much colder than optimum for egg survival of <br />11 <br />