title: Impact of parasites on salmon recruitment in the Northeast Atlantic Ocean.
abstract: Parasites may have large effects on host population dynamics, marine fisheries and conservation, but a clear elucidation of their impact is limited by a lack of ecosystem-scale experimental data. We conducted a meta-analysis of replicated manipulative field experiments concerning the influence of parasitism by crustaceans on the marine survival of Atlantic salmon (Salmo salar L.). The data include 24 trials in which tagged smolts (totalling 283 347 fish; 1996-2008) were released as paired control and parasiticide-treated groups into 10 areas of Ireland and Norway. All experimental fish were infection-free when released into freshwater, and a proportion of each group was recovered as adult recruits returning to coastal waters 1 or more years later. Treatment had a significant positive effect on survival to recruitment, with an overall effect size (odds ratio) of 1.29 that corresponds to an estimated loss of 39 per cent (95% CI: 18-55%) of adult salmon recruitment. The parasitic crustaceans were probably acquired during early marine migration in areas that host large aquaculture populations of domesticated salmon, which elevate local abundances of ectoparasitic copepods-particularly Lepeophtheirus salmonis. These results provide experimental evidence from a large marine ecosystem that parasites can have large impacts on fish recruitment, fisheries and conservation.
authors.affiliation: Department of Zoology, University of Otago, Dunedin, New Zealand. martin.krkosek@otago.ac.nz
authors.forename: Martin
authors.initials: M
authors.lastname: Krkosek
authors.forename: Crawford W
authors.initials: CW
authors.lastname: Revie
authors.forename: Patrick G
authors.initials: PG
authors.lastname: Gargan
authors.forename: Ove T
authors.initials: OT
authors.lastname: Skilbrei
authors.forename: Bengt
authors.initials: B
authors.lastname: Finstad
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Todd
mesh_terms: D000818:Animals; D000977:Antiparasitic Agents / Q000494:pharmacology*; D017756:Aquaculture; D033342:Copepoda / Q000187:drug effects* / Q000502:physiology; D004478:Ectoparasitic Infestations / Q000453:epidemiology / Q000469:parasitology / Q000517:prevention & control / Q000662:veterinary*; D005393:Fish Diseases / Q000453:epidemiology* / Q000469:parasitology / Q000517:prevention & control; D007494:Ireland; D008954:Models, Biological; D009664:Norway; D010273:Parasitic Diseases, Animal / Q000453:epidemiology* / Q000469:parasitology / Q000517:prevention & control; D011157:Population Dynamics; D012474:Salmon
chemical_list: D000977:Antiparasitic Agents