7030 - Laserfiche WebLink

Home Browse Search

Progressing upstream, the habitat becomes more diverse, a condition which may be better suited for endemic fish. The lower section of the White River is also utilized for irrigation which may cause deterioration of the river habitat through increased siltation and nutrient loads, a condition in which exotics are particularly sucessful. Threatened and Endangered Endemic Fish Colorado Squawfish (Ptychocheilus lucius) The squawfish was originally found throughout the entire Colorado River basin, but its distribution has been greatly reduced by man's alterations to the system. In southern Utah it is restricted to the Green and Colorado Rivers. Holden and Stalnaker (1975a) considered it rare in collections made in the Green River in Desolation Canyon and in the Green and Colorado Rivers in Canyonlands National Park. The life history and ecology of the squawfish has recently been reviewed (Seethaler, 1978). Six adult squawfish were captured in the lower 12.2 mi (19.6 km) of the White River during this study. Three were collected on July 11 and three on September 28 while electrofishing from a boat. At least seven other squawfish were "observed" in this section of the river. Observed fish were those identified from the electrofishing boat by a qualified individual (Delmar Robinson, member of the squawfish recovery team), but were able to avoid capture. This is the first report of squawfish in the Utah portion of the White River and represents an extension of their known distribution. As mentioned earlier, squawfish have been commonly found in the Green River near the confluence of the White River. Prewitt et al. (1978) found two squawfish in the Colorado portion of the White River (84 km, 52 mi upstream from the Utah border) during 1977, a year of extreme drought. Squawfish were not collected by surveys in the same area the following year, a normal water year (D. Snyder, Colorado State University, personal communication). A squawfish was recently found for the first time in the San Rafael River, 5 mi (8 km) from the confluence with the Green (McAda et al., 1977). During drought conditions, perhaps the fish utilize areas further upstream. Seethaler (1978) characterized the fish as a "probing, wandering, opportunist" which can be found throughout the Green and Colorado River and adjacent waters in search of prey. The captured fish ranged in length from 444 mm to 620 mm and in weight from 590 g to 1066 g. According to information presented by Seethaler (1978), Squawfish 400 mm in length are 6 years old, those 500 mm in length are 9 years old and those 600 mm in length are 11 years old. Based on this information,