The Evolutionary Legacy of Size-selective Fisheries

Size-selective fishing has the potential to cause changes in life-history traits, which are often at least moderately heritable. Thus, size-selective fishing has the potential to cause genetic changes in exploited populations. We subjected experimentally populations of wild zebrafish (Danio rerio) to size-selective harvest over five generations by establishing three treatment groups: selection for large, random and small body size and focused on three questions that have been thus far only partially studied experimentally in the fisheries context: 1) How do the three important life-history traits, maturation, growth and reproductive investment, collectively respond to size-selective harvesting? 2) How the potential changes in life-history traits affect population growth rates? 3) Can size-selective harvesting induce rapid molecular-level responses in the experimentally exploited populations? Five generations of size-selective harvesting induced changes in growth rate and reproductive investment among the selection lines. Size-selective harvesting further induced changes in population growth rates, such that small-size selected fish adapted to size-selective fishing environment and had higher population growth rate compared to the other selection treatments. However, in the absence of fishing small-size selected fish had significantly lower population growth rate. Thus, our results suggest that size-selective fishing might impair the recovery potential of the exploited stocks. Finally, we show that size-selective harvesting induced rapid and replicable genetic changes in the experimentally exploited fish populations. Our study contributes to the understanding of the rate of phenotypic and evolutionary changes in size-selective fisheries and suggests that fisheries-induced evolution is not necessarily a long-term process but it can be rapid and may become a short-term concern in the fisheries management.