POPULATION VIABILITY OF THE SNAKE RIVER CHINOOK SALMON (ONCORHYNCHUS-TSHAWYTSCHA)

In the presence of historical data, population viability models of int ermediate complexity can be parameterized and utilized to project the consequences of various management actions for endangered species. A g eneral stochastic population dynamics model with density feedback, age structure, and autocorrelated environmental fluctuations was construc ted and parameterized for best fit over 36 years of spring chinook sal mon (Oncorhynchus tshawytscha) redd count data in five Idaho index str eams. Simulations indicate that persistence of the Snake River spring chinook salmon population depends primarily on density-independent mor tality. Improvement of rearing habitat, predator control, reduced fish ing pressure, and improved dam passage all would alleviate density-ind ependent mortality. The current value of the Ricker alpha should provi de for a continuation of the status quo. A recovery of the population to 1957-1961 levels within 100 years would require an approximately 75 % increase in survival and (or) fecundity. Manipulations of the Ricker beta are likely to have little or no effect on persistence versus ext inction, but considerable influence on population size.