title: Harvest-induced disruptive selection increases variance in fitness-related traits.
abstract: The form of Darwinian selection has important ecological and management implications. Negative effects of harvesting are often ascribed to size truncation (i.e. strictly directional selection against large individuals) and resultant decrease in trait variability, which depresses capacity to buffer environmental change, hinders evolutionary rebound and ultimately impairs population recovery. However, the exact form of harvest-induced selection is generally unknown and the effects of harvest on trait variability remain unexplored. Here we use unique data from the Windermere (UK) long-term ecological experiment to show in a top predator (pike, Esox lucius) that the fishery does not induce size truncation but disruptive (diversifying) selection, and does not decrease but rather increases variability in pike somatic growth rate and size at age. This result is supported by complementary modelling approaches removing the effects of catch selectivity, selection prior to the catch and environmental variation. Therefore, fishing most likely increased genetic variability for somatic growth in pike and presumably favoured an observed rapid evolutionary rebound after fishery relaxation. Inference about the mechanisms through which harvesting negatively affects population numbers and recovery should systematically be based on a measure of the exact form of selection. From a management perspective, disruptive harvesting necessitates combining a preservation of large individuals with moderate exploitation rates, and thus provides a comprehensive tool for sustainable exploitation of natural resources.
authors.affiliation: UPMC-Paris6, UMR (CNRS) 7618, Laboratoire Biogéochimie et Ecologie des Milieux Continentaux, 46 rue d'Ulm, F-75230 Paris Cedex 05, France. edeline@biologie.ens.fr
authors.forename: Eric
authors.initials: E
authors.lastname: Edeline
authors.forename: Arnaud
authors.initials: A
authors.lastname: Le Rouzic
authors.forename: Ian J
authors.initials: IJ
authors.lastname: Winfield
authors.forename: Janice M
authors.initials: JM
authors.lastname: Fletcher
authors.forename: J Ben
authors.initials: JB
authors.lastname: James
authors.forename: Nils Chr
authors.initials: NC
authors.lastname: Stenseth
authors.forename: L Asbjørn
authors.initials: LA
authors.lastname: Vøllestad
mesh_terms: D000818:Animals; D005075:Biological Evolution; D049628:Body Size; D017859:Esocidae / Q000235:genetics / Q000254:growth & development*; D005398:Fisheries / Q000379:methods / Q000706:statistics & numerical data*; D014644:Genetic Variation; D016013:Likelihood Functions; D008962:Models, Theoretical; D010641:Phenotype; D011157:Population Dynamics; D012641:Selection, Genetic; D006113:United Kingdom