by Richard W. Zabel
University of Washington
Chairperson of the Supervisory Committee: Professor James J. Anderson
Fisheries Research Institute
The downstream migration of juvenile salmon is a critical phase of salmon life history. Individuals are susceptible to mortality from a variety of sources, and in the Columbia River system, hydroelectric dams are a further source of mortality. Models that describe the spatial and temporal distribution of populations of fish can aid in the understanding of juvenile salmon behavior and can be used as management tools. This dissertation presents several models of the distribution of migrating juvenile salmonids. The models are derived from diffusion equations and are expressed as probablity density functions. Likelihood functions are formulated from the probability densities and data, and parameter estimation and alternative model comparison are based on the likelihoods.
A two parameter travel time model is effective at describing the arrival time distributions of run-of-the-river, yearling chinook. One of the parameters determines the rate of downstream migration; the other parameter determines the rate of population spreading. After model parameters are related to date of release and river flow in a nonlinear regression equation, the model is used predictively. With subyearling chinook, a delay term, which represents delay in the initiation of migration, substantially improves the travel time model. In addition, fish length is determined to be important in modeling sockeye and subyearling chinook travel time. The vertical distribution of juvenile salmonids in the forebay is modeled based on a chemotaxis equation, where the fish cue on light intensity. The correspondence between the model and data is good.