BC CAHS says sea lice not resistant to treatment

Published: Friday, February 19, 2010

The article “Sea lice issues cause concern” (February 12, 2010) requires comment. I was disappointed that even though Campbell River is home to a research facility with expertise in this field, the BC Centre for Aquatic Health Sciences, the BC CAHS was not contacted for input. Our independent research facility works with a wide variety of stakeholders including government, NGOs and industry to find solutions to aquatic health concerns and we would have been pleased to provide comment on this issue.

Based on our research, there is no indication that sea lice in BC are resistant to the louse treatment, SLICE®. Several factors reduce the opportunity to develop SLICE®-resistant lice. First, the dilution effect: the large numbers of BC’s wild salmon populations, which are sea lice hosts, greatly outnumber BC farmed salmon populations. Since these large numbers of wild salmon never receive SLICE® treatment, the numbers of untreated sea lice on wild fish vastly outnumber lice populations (treated or not) on farmed salmon. As resistance is the result of repeated exposure, the overwhelming numbers of untreated lice (on wild salmon) on the BC coast mean that creation of a resistant population is unlikely. Second, few SLICE® treatments (especially in comparison to other salmon farming areas) and effective use of this medicine on BC salmon farms means there is less opportunity to develop resistance.

Regarding comments on transport of sea lice following harvest, sea lice embryos like all marine invertebrates are very fragile and; therefore, unlikely to survive the changes in oxygen amount, salinity and temperature that occur during harvest, transport and processing. Our researchers and technicians have been involved in studying the plankton in Discovery Passage for the past four years to assist the Quinsam Hatchery in assessing the best time to release its coho to increase early survival. Throughout this study period, despite repeated and detailed monitoring from February to June which includes the period of juvenile wild salmon outmigration, no developing (young) sea lice were found in the Discovery Passage.

Dialogue about aquatic health issues needs to be constructive and factual. This is particularly true as jurisdiction for aquaculture moves from provincial to federal authority. Anyone seeking additional information about the health of Campbell River’s aquatic environment is always welcome to contact us.

Dr. Sonja Saksida, Executive Director
BC Centre for Aquatic Health Sciences


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