GROWTH AND LONGEVITY OF GOLDEN TROUT, ONCORHYNCHUS-AGUABONITA, IN THEIR NATIVE STREAMS

Golden trout, Oncorhynchus aguabonita, from 17 streams in the Kern Plateau region of the Sierra Nevada, California, were aged using otoliths, and growth rates were determined using length-age and weight-age relationships. Growth rates, condition factors, and densities of trout were correlated with site-specific biological and physical factors using stepwise multiple regression techniques. These stream populations were highly stunted, and individuals attained quite old ages (9 years). Densities were usually low and high density had a significant negative effect on growth (P < 0.001). In addition, growth was positively affected by amount of aquatic vegetation, amount of bank vegetation, stream channel stability, and elevation. While site-specific factors such as trout density may influence trout growth, the low growth rates throughout the study area were probably due to the low productivity of these unstable montane streams and the short growing period at high elevations.