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downstream. For each habitat segment that the juveniles have to move through in <br />moving downstream, a proportion die based upon the juvenile mortality rate for <br />dispersal. This means that the further a juvenile has to move downstream, the less <br />likely it is to survive. <br />4. At the end of each time step (1 year), the number of survivors in each age category <br />become one year older, except for adults, the terminal age class. The age-specific <br />survivorship rates for each year are randomly generated based upon empirically <br />derived estimates ± randomly generated standard-normal deviates. The standard- <br />normal deviate depends upon the observed standard deviation for each age-specific <br />mortality rate. <br />5. The processes of 1- 4 are repeated for the next year, etc. <br />By generating the population dynamics for 100 years for 100 replicated populations, <br />the percentage of populations that fall below-the hypothesized extinction threshold <br />(minimum number of individuals) or any management-derived target values denotes the <br />likelihood that the population will persist for i 00 years. <br />Final Model De cription <br />Because most managers in the Upper Basin are not familiar with, nor have access to <br />11 <br />