Transactions of the American Fisheries Society 126:687-698. 1997 © Copyright by the American Fisheries Society 1997 Growth and Survival of Colorado Squawfish in the Upper Colorado River

Abstract.—Growth and adult survival rates were estimated for the endangered Colorado squaw-fish Ptychocheilus Indus inhabiting the upper Colorado River by using data from fish captured during 1990-1995. Mean annual growth rates of fish aged 3-6 years ranged from 32.2 (age 6) to 82.0 (age 3) mm/year. Growth rates for older fish were highest for fish 400-449 mm total length, TL, (42.7 mm/year) and declined to 19.8 mm/year for fish 500-549 mm TL. Fish 550 mm and longer grew an average 9.5 mm/year. Survival rates for fish 550 mm and longer were estimated by comparing measured size distributions with simulated stable age and size distributions; these ranged from 0.83-0.87. with the best fit at 0.85. Though lack of historical data precludes com-parisons with past growth and survival rates, our data serve as a baseline for future population monitoring efforts. Growth and survival rates, fundamental com-ponents of most demographic studies, are essential to understanding population dynamics and requi-site to formulating recovery and management strategies for endangered species. The Colorad