Recreational fishing selectively captures individuals with the highest fitness potential

Abstract

Fisheries-induced evolution and its impact on the productivity of exploited fish stocks remains a highly contested research topic in applied fish evolution and fisheries science. Although many quantitative models assume that larger, more fecund fish are preferentially removed by fishing, there is no empirical evidence describing the relationship between vulnerability to capture and individual reproductive fitness in the wild. Using males from two lines of largemouth bass (Micropterus salmoides) selectively bred over three generations for either high (HV) or low (LV) vulnerability to angling as a model system, we show that the trait "vulnerability to angling" positively correlates with aggression, intensity of parental care, and reproductive fitness. The difference in reproductive fitness between HV and LV fish was particularly evident among larger males, which are also the preferred mating partners of females. Our study constitutes experimental evidence that recreational angling selectively captures individuals with the highest potential for reproductive fitness. Our study further suggests that selective removal of the fittest individuals likely occurs in many fisheries that target species engaged in parental care. As a result, depending on the ecological context, angling-induced selection may have negative consequences for recruitment within wild populations of largemouth bass and possibly other exploited species in which behavioral patterns that determine fitness, such as aggression or parental care, also affect their vulnerability to fishing gear.

Fig. 1.

(A) Number of eggs in individual largemouth bass nests of males with high vulnerability to angling (HV, full circles and solid lines) and low vulnerability to angling (LV, open circles and dashed lines), (B) duration (days) of parental care (starting at swim-up fry stage) provided by the nest-guarding males, and (C) number of genotyped fall recruits across nest-guarding males of different sizes.

Fig. 2.

(A) Nest-guarding intensity score and (B) aggression score (as measured by hits to fishing lures) for male largemouth bass guarding eggs with high vulnerability to angling lures (HV), and low vulnerability to angling lures (LV). Data are shown as box plot showing the median (solid line) and mean (dashed line).