Harvest-induced evolution and effective population size Evolutionary Applications

Much has been written about fishery-induced evolution (FIE) in exploited species, but relatively little attention has been paid to the consequences for one of the most important parameters in evolutionary biology-effective population size (Nₑ). We use a combination of simulations of Atlantic cod populations experiencing harvest, artificial manipulation of cod life tables, and analytical methods to explore how adding harvest to natural mortality affects Nₑ, census size (N), and the ratio Nₑ/N. We show that harvest-mediated reductions in Nₑ are due entirely to reductions in recruitment, because increasing adult mortality actually increases the Nₑ/N ratio. This means that proportional reductions in abundance caused by harvest represent an upper limit to the proportional reductions in Nₑ, and that in some cases Nₑ can even increase with increased harvest. This result is a quite general consequence of increased adult mortality and does not depend on harvest selectivity or FIE, although both of these influence the results in a quantitative way. In scenarios that allowed evolution, Nₑ recovered quickly after harvest ended and remained higher than in the preharvest population for well over a century, which indicates that evolution can help provide a long-term buffer against loss of genetic variability. 2016 27247617 PMC4869408 NMFS (National Marine Fisheries Service) NWFSC (Northwest Fisheries Science Center) PMC http://dx.doi.org/10.1111/eva.12373 CC BY 1951