Reviews in Fisheries Science, 14:1–11, 2006
Copyright © Taylor & Francis Inc.
ISSN: 1064-1262 print
DOI: 10.1080/10641260500433531
Fish Farms and Sea Lice Infestations of Wild Juvenile Salmon in the Broughton Archipelago—A Rebuttal to Brooks (2005)
MARTIN KRKOˇSEK,1,2,3 MARK A. LEWIS,1,2
JOHN P. VOLPE,3 AND ALEXANDRA MORTON4
1Center for Mathematical Biology, Department of Mathematical and Statistical
Sciences, University of Alberta, Edmonton, Alberta, Canada
2Department of Biological Sciences, University of Alberta, Edmonton,
Alberta, Canada
3School of Environmental Studies, University of Victoria, Victoria,
British Columbia, Canada
4Raincoast Research Society, Simoom Sound, British Columbia, Canada
Contrary to several recent studies, a review (Brooks, 2005) of sea lice (Lepeophtheirus salmonis) interactions between wild and farm salmon in the Broughton Archipelago, British Columbia, Canada, concluded that there is little potential for sea lice transmission from farm to wild salmon. In this rebuttal, we show that this conclusion was based on a flawed interpretation of how salinity affects louse development, a misunderstanding of how the timing of salinity changes corresponds to the timing of the juvenile salmon migration, models of larval dispersion that overestimate the transport of louse larvae, and a selective and misleading assessment of the literature. We analyze and extend the current models of larval dispersion and demonstrate the (perhaps counter-intuitive) result that sustained high abundances of infectious larvae should be expected near liceinfested salmon farms. We also highlight important studies overlooked in Brooks (2005) and clarify some misinterpretations. Counter to the conclusions in Brooks (2005), the modeling and empirical work to date on sea lice interactions between wild and farm salmon are consistent and point to a strong association between salmon farming and recurrent infestations of wild juvenile salmon in the Broughton Archipelago.
Keywords sea lice, aquaculture, salmon, parasite, dispersion, transmission dynamics, reservoir host, emerging disease
Introduction
There can be little doubt that temperature, salinity, and site-specific oceanographic features affect the spread of planktonic larval sea lice (Lepeophtheirus salmonis and Caligus spp.) released from salmon aquaculture installations in the nearshore environment. In a recent review of sea lice interactions between wild and farm salmon in the Broughton Archipelago, British Columbia, Brooks (2005) argues that these effects combine to prevent the transmission of lice from farm salmon to sympatric wild juvenile pink (Oncorhynchus gorbuscha) and chum (O. keta) salmon. The conclusions in Brooks (2005) conflict with several empirical studies conducted on the effect of salmon farms on sea lice infestations of wild juvenile salmon in the Broughton Archipelago. These studies clearly demonstrate the transmission of lice from farm salmon to wild juvenile salmon (Morton andWilliams, 2004; Morton et al., 2004; Krkoˇsek et al., 2005a; Morton et al., 2005). Here we attempt to reconcile this discrepancy by assessing the salinity data, larval dispersion models, and arguments used by Brooks (2005) to arrive at his conclusions. We show where Brooks (2005) goes wrong and how the models, data, and literature point to a strong association between salmon farms and recurrent sea lice infestations of juvenile salmon in the Broughton Archipelago.
http://www.adopt-a-fry.org/wp-content/uploads/file/Rebuttal to Brooks.pdf
