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 [USA] 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 1959-1977 in a test stretch of the Au Sable River agree quite well with the computations.