PLoS ONE |
www.plosone.org 1 February 2011 | Volume 6 | Issue 2 | e16851
Sea Louse Infection of Juvenile Sockeye Salmon in Relation to Marine Salmon Farms on Canada’s West Coast
Michael H. H. Price1,2*, Stan L. Proboszcz3, Rick D. Routledge4, Allen S. Gottesfeld5, Craig Orr3, John D. Reynolds6
1 Department of Biology, University of Victoria, Victoria, Canada,
2 Raincoast Conservation Foundation, Sidney, Canada,
3 Watershed Watch Salmon Society, Coquitlam, Canada,
4 Department of Statistics and Actuarial Science, Simon Fraser University, Burnaby, Canada,
5 Skeena Fisheries Commission, Hazelton, Canada,
6 Earth to Ocean Research Group, Department of Biology, Simon Fraser University, Burnaby, Canada
Abstract
Background: Pathogens are growing threats to wildlife. The rapid growth of marine salmon farms over the past two decades has increased host abundance for pathogenic sea lice in coastal waters, and wild juvenile salmon swimming past farms are frequently infected with lice. Here we report the first investigation of the potential role of salmon farms in transmitting sea lice to juvenile sockeye salmon (Oncorhynchus nerka). Methodology/Principal Findings: We used genetic analyses to determine the origin of sockeye from Canada’s two most important salmon rivers, the Fraser and Skeena; Fraser sockeye migrate through a region with salmon farms, and Skeena sockeye do not. We compared lice levels between Fraser and Skeena juvenile sockeye, and within the salmon farm region we compared lice levels on wild fish either before or after migration past farms. We matched the latter data on wild juveniles with sea lice data concurrently gathered on farms. Fraser River sockeye migrating through a region with salmon farms hosted an order of magnitude more sea lice than Skeena River populations, where there are no farms.
Lice abundances on juvenile sockeye in the salmon farm region were substantially higher downstream of farms than upstream of farms for the two common species of lice: Caligus clemensi and Lepeophtheirus salmonis, and changes in their proportions between two years matched changes on the fish farms. Mixed-effects models show that position relative to salmon farms best explained C. clemensi abundance on sockeye, while migration year combined with position relative to salmon farms and temperature was one of two top models to explain L. salmonis abundance.
Conclusions/Significance: This is the first study to demonstrate a potential role of salmon farms in sea lice transmission to juvenile sockeye salmon during their critical early marine migration. Moreover, it demonstrates a major migration corridor past farms for sockeye that originated in the Fraser River, a complex of populations that are the subject of conservation concern.
Citation: Price MHH, Proboszcz SL, Routledge RD, Gottesfeld AS, Orr C, et al. (2011) Sea Louse Infection of Juvenile Sockeye Salmon in Relation to Marine Salmon Farms on Canada’s West Coast. PLoS ONE 6(2): e16851. doi:10.1371/journal.pone.0016851
Editor: Brock Fenton, University of Western Ontario, Canada
Received September 17, 2010; Accepted January 13, 2011; Published February 9, 2011
Copyright: 2011 Price et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: The work was funded by: The Coastal Alliance for Aquaculture Reform (
www.farmedanddangerous.org), David and Lucile Packard Foundation (
www.packard.org), Gordon and Betty Moore Foundation (
www.moore.org), Patrick Hodgson Family Foundation, Ritchie Foundation, Sandler Family Foundation, SOS Marine Conservation Foundation (
www.saveoursalmon.ca), Tom Buell Endowment Fund, a Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grants to RD Routledge and JD Reynolds (
www.nserc-crsng.gc.ca), and an NSERC Industrial Postgraduate Scholarship to MHH Price. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing Interests: The authors have declared that no competing interests exist.
E-mail:
pricem@uvic.ca