Impacts of angling induced selection on aggression, nest guarding behavior and reproductive success of male largemouth bass (Micropterus salmoides)

Few empirical studies have evaluated the consequences of angling-induced evolution for the fitness in fish. The present study examines the impacts of recreational fishing-induced selection on behaviour and reproductive success using two lines of largemouth bass (Micropterus salmoides) selected for high (HVF) and low vulnerability to angling (LVF) over three consecutive generations. This species offers a suitable model to study the behavioural mechanisms leading to fisheries induced evolution and the impacts of such evolution for fitness, because male LMB guard nests during spawning and provide extended parental care. During this time, they are highly vulnerable to harvest providing ample opportunity for fisheries induced evolution even without harvesting because during catch-and-release nest predation can reduce the fitness of males. I tested the hypothesis that known behavioral and physiological differences between HVF and LVF are important for parental care and influencing reproductive success. To test this hypothesis, similarsized male HVF (N = 24) and male LVF (N = 24) were stocked together with unselected female largemouth bass into common ponds (N = 6) prior to spawning. Along with behavioral observations during spawning, the final fall recruitment of individual males was assessed through the analysis of microsatellites and assigning offspring to individual parents (N = 200 offspring per pond). When providing parental care HVF were found to stay longer times on nest and to be more vulnerable to fishing lures compared to LVF. Furthermore, fall recruitment was highest for large HVF males. The study revealed that reproductive success of largemouth bass is likely dependent on behavioural and physiological characteristics, influencing the duration and intensity of provided parental care. This suggests that the reproductive fitness of male HVF is indeed larger compared to the fitness of male LVF. Our findings underscore the notion that in wild population selective removal of fish expressing the strongest parental care might negatively impact population recruitment. From a management perspective, non-selective exploitation is encouraged to avoid evolutionary repercussions for the viability of wild LMB populations resulting from recreational fishing.