Growth and Recruitment in Experimentally Exploited Lake Whitefish (Coregonus clupeaformis) Populations

From 1971 to 1978 I conducted an exploitation experiment on lake whitefish (Coregonus clupeaformis) in four Northwest Territories lakes. The objective was to test the hypotheses that, when exploited, growth and recruitment would increase in the populations, and that the degree of increase would be proportional to the intensity of exploitation. Significant increases in size-at-age were recorded in the exploited lakes, and the degree and persistence of the increase were proportional to the intensity of exploitation. Good recruitment was stimulated in the heavily exploited lake, and to a lesser degree in the moderately exploited lake. The hypotheses were, therefore, corroborated. Analyses of growth and year-class strength in the unexploited control lake and the lightly exploited lake indicated that natural variation in growth and recruitment, on a similar scale to that stimulated by exploitation, had occurred in the past. The compensatory responses of lake whitefish populations to exploitation appear to be a logical consequence of the natural population regulating mechanisms for the species. The results of my experiment indicate that in unexploited lakes, recruitment and growth of young fish is regulated by the established population of mature fish.