4. Fisheries Induced Evolution in Largemouth Bass – Reductions in Parental Care and Vulnerability to Angling

Long-term studies in Ontario, Canada on largemouth bass have clearly demonstrated that angling nesting males (both catch-and-harvest and catch-and-release) can have negative impacts on the reproductive success for the captured individual. Unfortunately, the male bass that are the most capable of having the greatest relative contribution to the year class are also those individuals that provide the best and longest parental care for their offspring.  As a result, within the population those males are also the most aggressive and hence, the most vulnerable to angling. We postulate that angling for nesting bass results in selection against the “best dads” in a population, and the result is the evolution of the population to become less aggressive thereby diminishing parental care attributes, a classic example of Fisheries Induced Evolution (FIE).  Controlled, long-term selective breeding experiments over 20+ years have documented the heritability of vulnerability of bass to angling. Controlled reproductive competition experiments further demonstrated that the highly vulnerable (HV) strain of bass indeed had greater reproductive success than the less vulnerable strain (LV)…because the LV bass had lower mating success and provided less parental care for their offspring than did their HV counterparts.  Because angling for largemouth bass has been occurring on many of our bass populations for many years, we also predicted that there should be some evidence in the wild of this FIE.  In fact, the level of vulnerability to angling of nesting male largemouth bass in lakes that have had little to no exploitation is significantly greater than that observed for nesting males in moderately and heavily angled populations.  The long-term impacts of angling bass during the reproductive season is presented in the form of a conceptual model that serves as the basis for recommendations on what management changes are needed to assure long-term sustainability of wild populations.