Responses of a Fish Population Model to Young-of-the-Year Mortality

A multiple-age-class model is used to examine the effects of increases in density-independent young-of-the-year mortality caused by power plant entrainment of larval fish. It is demonstrated analytically that in all realistic cases, an increase in such mortality results in a smaller equilibrium population density of adult fish. The stability of the population with respect to perturbations about its equilibrium point is increased in these cases. However, situations can occur where a slight increase in mortality causes a catastrophic population decline. The model is used to generate autoregression graphs of population numbers that can be compared with field data.