The Effects of a Simulated Angler Harvest on Biomass and Production in Lightly Exploited Populations of Smallmouth and Largemouth Bass

Abstract

Harvests of 13 to 21%, mostly of larger, older fish, were imposed for two years on populations of smallmouth and largemouth bass (Micropterus dolomieui and M. salmoides) that previously had been virtually unfished. Another population of smallmouth bass served as a control. Using trap nets, estimates of the number of bass and their size were made for one year before and two years after initial harvest. From these data, annual natural mortality, growth, standing crop and production were computed. There were no strong and consistent changes in any parameter which could be attributed to reductions in numbers of fish. Changes in growth unrelated to population density apparently resulted in declines of ratios of production to biomass following harvest. Possible causes of the lack of compensatory responses to harvest include the relatively short period of study and time lag in changes in growth and mortality.