title: Harvest-induced evolution and effective population size.
abstract: 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 (N e). 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 N e, census size (N), and the ratio N e/N. We show that harvest-mediated reductions in N e are due entirely to reductions in recruitment, because increasing adult mortality actually increases the N e/N ratio. This means that proportional reductions in abundance caused by harvest represent an upper limit to the proportional reductions in N e, and that in some cases N e 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, N e 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.
authors.affiliation: Department of Environmental Sciences University of Helsinki Helsinki Finland.
authors.forename: Anna
authors.initials: A
authors.lastname: Kuparinen
authors.affiliation: Department of Biology Dalhousie University Halifax NS Canada; Department of Biosciences Centre For Ecological and Evolutionary Synthesis University of Oslo Oslo Norway; Department of Natural Sciences University of Agder Kristiansand Norway.
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Hutchings
authors.affiliation: National Marine Fisheries Service National Oceanic and Atmospheric Administration Northwest Fisheries Science Center Seattle WA USA.
authors.forename: Robin S
authors.initials: RS
authors.lastname: Waples
keywords: contemporary evolution; fisheries management; life history evolution; population genetics – empirical; wildlife management