DAO 75:229-238 (2007)  -  doi:10.3354/dao075229

Differential rejection of salmon lice by pink and chum salmon: disease consequences and expression of proinflammatory genes

Simon R. M. Jones1,*, Mark D. Fast2, Stewart C. Johnson2, David B. Groman3

1Pacific Biological Station, 3190 Hammond Bay Road, Fisheries and Oceans Canada, Nanaimo, British Columbia V9T 6N7, Canada
2Institute for Marine Biosciences, National Research Council, 1411 Oxford Street, Halifax, Nova Scotia B3H 3Z1, Canada
3Aquatic Diagnostic Services, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island C1A 4P3, Canada

ABSTRACT: The consequences of high (735 copepodids fish–1) and low (243 copepodids fish–1) level exposures of size-matched juvenile pink and chum salmon to Lepeophtheirus salmonis copepodids were examined. At both levels of exposure the prevalence and abundance of L. salmonis was significantly higher on chum salmon. In addition, the weight of exposed chum salmon following the high exposure was significantly less than that of unexposed chum salmon. At both exposures, the haematocrit of exposed chum salmon was significantly less than that of unexposed chum. Neither weight nor haematocrit of pink salmon was affected by exposures at these levels. Despite the presence of microscopic inflammatory lesions associated with attachment of L. salmonis on the epithelium of gill and fin of both salmon species, there were no mortalities following either exposure. A transient cortisol response was observed in chum salmon 21 d after low exposure. An earlier and quantitatively higher expression of the proinflammatory genes interleukin-8 (IL-8), tumour necrosis factor α-1 (TNFα-1) and interleukin-1β (IL-1β) in fin and head kidney of pink salmon suggested a mechanism of more rapid louse rejection in this species. Together, these observations indicate a relatively enhanced innate resistance to L. salmonis in the juvenile pink salmon compared with the juvenile chum salmon.


KEY WORDS: Oncorhynchus gorbuscha · Oncorhynchus keta · Lepeophtheirus salmonis · Sea lice · Immune response


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