Research & Reports: 2009
2009, September – R. Beamish, J. Wade, W. Pennell, E. Gordon, S. Jones, C. Neville, K. Lange, and R. Sweeting. A large, natural infection of sea lice on juvenile Paciﬁc salmon in the Gulf Islands area of British Columbia, Canada.
During two sampling episodes in June and July 2008, 502 juvenile salmon were examined for sea lice via purse seine along the southern Gulf Islands (primarily Salt Spring Island). Abundant lice levels were found and since there were no active fish farms in the area, this paper provides evidence that high levels of louse infestation on juvenile salmon can and do occur naturally. The majority of lice were Caligus clemensi—a generalist louse species—with herring a likely source (as has been shown in Europe and the subsequent infestations of salmon farms).
It is important to note that the data gathered in this paper cannot be assumed to represent the population as a whole because the sample size and number of collection periods are small (i.e., 502 juvenile salmon examined over 5 days in a single year). In addition, the Gulf Islands region is known to harbour higher lice levels than other ‘natural areas’ of BC’s coast.
2009, August – Obee, Nicole. Chemical and Biological Remediation of Marine Sediments at a Fallowed Salmon Farm, Centre Cove, Kyuquot Sound, B.C.
A study by the British Columbia Ministry of Environment examines the impacts of waste deposits in the sediment of a fallowed open net pen salmon farm on the West Coast of Vancouver Island. In operation for 22 years until 2002, the site was analyzed for sulphide, copper and zinc concentrations and oxidation reduction potential.
The research suggests that it could take up to 15 years of fallowing for sulphide concentrations to return to original conditions. This is a long timeframe and suggests that sites in areas with slow current speeds and highly depositional environments are not well-suited for aquaculture operations. The study also shows that heavy metals like zinc and copper do not always decline with time and may be toxic to marine life attempting to recover in the area.
2009, July – Barker, D. E., L. M. Braden, M. P. Coombs and B. Boyce. Preliminary studies on the isolation of bacteria from sea lice. Lepeophtheirus salmonis, infecting farmed salmon in British Columbia, Canada. Parasitology Research 105:1173-1177
Many parasitic species are vectors of pathogens which can cause disease. For example, mosquitoes can spread organisms that cause malaria. In this study, the researchers examined sea lice from farmed salmon in BC and found three different species of potential disease causing bacteria. These species were found on the surface and inside the gut of sea lice. They also found the prevalence of the bacteria was higher among lice during warmer months and on adult sea lice. Follow-up research is planned to determine if sea lice can spread these bacteria and diseases from farmed to wild fish.
2009, July – Costello, Mark J. How sea lice from salmon farms may cause wild salmonid declines in Europe and North America and be a threat to fishes elsewhere. Proceedings of the Royal Society of London Series B.
Dr. Mark Costello from the University of Auckland published a review paper summarizing declines in wild salmon populations and the link to sea lice from salmon farms in Europe and North America. It is believed that Lepeophtheirus salmonis (salmon louse) may be transported to intercept migrating salmonid hosts by swimming to the surface during daylight where the onshore wind moves the surface water towards the shore and into estuaries. Countries that produce the most farmed salmonids have a problem with sea lice on farms whereas countries not producing high volumes do not, This suggests a relationship exists between the number of farms and/or farmed ﬁshes, and the development of sea lice infestations on farms. He concludes the evidence that salmon farms are the most signiﬁcant source of the epizootics of sea lice on juvenile wild salmonids in Europe and North America is now convincing.
2009, May – M. Krkosek, Morton, A., Volpe, J. and Lewis, M. 2009. Sea lice and salmon population dynamics: Effects of exposure time for migratory fish. Proceedings of the Royal Society of London Series B.
The authors examined the process of sea louse transfer to wild juvenile salmon, specifically the period of time the salmon were exposed to infective stages of lice and the importance of the exposure period with regards to interpreting experimental field results and lab results. Fish exposure time to lice is important. The lab studies conducted by Fisheries and Oceans Canada only expose fish to infective stages of lice for hours; however, in real life (as more accurately described by the field sampling studies) the wild salmon in the Broughton Archipelago are exposed to lice for weeks and sometimes months. Hours vs. months makes a big difference (of 2 to 3 orders of magnitude).