Potential consequences of reproductive behaviour and mating system complexity on fishery-induced evolution

No abstracts are to be cited without prior reference to the author.

Reproductive behaviour and mating system complexity may influence the rate of evolutionary change in exploited populations. Data on Atlantic cod (Gadus morhua) suggest that both sexes may prefer spawning with larger mates. In addition to potential mate selection, fecundity selection might also favour late-, large-maturing genotypes, in contrast to the selection imposed by many fisheries. Estimates of evolutionary change in fished populations have tended to exclude the possibility that reproductive success is influenced by the trait(s) under fisheries-induced selection. Here, we simulate changes to the mean and variance in body size concomitant with increased fishing intensity. Then, based on empirical data from the laboratory, we compare selection differentials (S) for length under the assumptions that size does and does not affect reproductive success. We find that the rate of decline in S with increased fishing pressure depends on: (a) the initial variance in body size; (b) changes to the variance in body size with increasing fishing intensity; and (c) the influence of size on reproductive success. If the initial variation in size is sufficiently high, and if the coefficient of variation (CV) in size increases with fishing intensity, the rate of change in S is less than that expected under the assumption that size has no effect on reproductive success. However, if the CV in body size remains constant, or declines, as fishing pressure increases, genetic change is predicted to be faster than that estimated under the assumption that size has no effect on reproduction. Our work underscores the potential importance of incorporating the consequences of reproductive behaviour and mating system complexity in estimates of evolutionary change in exploited resources.