Population-Genetic Study of the Effects of Selective Fishing on the Growth Rate of Trout

A mathematical model that simulates the effect of selective fishing on the size distributions of populations of trout is presented. The model assumes that the growth rate is genetically controlled by a small number of major genes. Empirical numbers for the growth and mortality rates of brown trout (Salmo trutta) in the Au Sable River of Michigan are used as input data. A computer is used to calculate the changes in the population subject to various degrees of fishing pressure for various size limits. Results are presented for periods of time ranging from 5–30 yr. The observed changes in the population over the period 1959 to 1977 in a test stretch of the Au Sable River agree quite well with the computations.