Laserfiche WebLink
spawning occurs between RK 26-32, and proto]arvae are caught in drift nets <br />20-30 km downstream of the spawning area (Haynes et al. 1984, Nesler et <br />al. 1988, this study). Radiotracking of spawning migrations have detected <br />no other spawning locations in the Green River Basin (Wick et al. 1983, <br />Tyus 1985). We are aware of no age-0 or age-1 juveniles captured in autumn <br />above the mouth of the Yampa River; an indication that the young fish do <br />not remain in the Yampa River. Annual seining results from our study show <br />autumn concentrations of age-0 Colorado squawfish approximately 150 km <br />downstream from the Yampa River spawning area. Finally, substrates in the <br />nursery areas are mostly fine silt and sand rather than cobbles and <br />boulder substrates that exist on the spawning areas (Tyus and McAda, <br />1984). <br />Although we do not have as extensive data in the lower Green River, we <br />presume that the same drift mechanism operates there. Years of <br />radiotracking migrating adults and collecting ripe fish there have <br />indicated that RK 225-257 is a major spawning area, and no other such area <br />has been located downstream. Larvae have been caught in drift nets 8 km <br />downstream (at RK 217) of the spawning area, and seining results show an <br />autumn concentration of age-0 Colorado squawfish approximately 130 km <br />downstream of the spawning area. Thus, data collected at the Green River <br />site support conclusions drawn from the Yampa River regarding larval <br />movement. <br />Nesler et al. (1988) describes potential sources of error in estimating <br />Colorado squawfish spawning dates from TL. Of particular concern is the <br />use of hatchery-derived growth equations for postlarvae. Average <br />temperatures in the Green River at mean larval hatching dates ranged from <br />13 <br />