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Diseases of Aquatic Organisms

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DAO 117:107-120 (2015)  -  DOI:

Wild juvenile salmonids in Muchalat Inlet, British Columbia, Canada: factors associated with sea lice prevalence

Ahmed Elmoslemany1,4, Crawford W. Revie1,*, Barry Milligan2, Lance Stewardson3, Raphael Vanderstichel

1Atlantic Veterinary College, University of Prince Edward Island, 550 University Ave, Charlottetown, Prince Edward Island C1A 4P3, Canada
2Grieg Seafood BC Ltd., 1180 Ironwood Street, Campbell River, British Columbia V9W 5P7, Canada
3Mainstream Biological Consulting, 1310 Marwalk Crescent, Campbell River, British Columbia V9W 5X1, Canada
4Present address: Hygiene and Preventive Medicine Department, Faculty of Veterinary Medicine, Kafrelsheikh University, Kafr el-Sheikh 35516, Egypt
*Corresponding author:

ABSTRACT: The Muchalat Inlet, British Columbia, is among the most westerly points at which aquaculture is practiced in Canada. In this paper, we summarise data from over 18000 wild fish sampled at 16 sites over an 8 yr period, between 2004 and 2011. The most prevalent wild species was chum salmon Oncorhynchus keta (82.4%), followed by Chinook O. tshawytscha (10%) and coho O. kisutch (4.3%). However, inter-annual and seasonal variation was evident, and smaller numbers of other Pacific salmon and stickleback species were sporadically observed. A high percentage of wild salmon (~95%) had no sea lice parasites present, with less than 1% of the fish hosting a mobile-stage sea louse. Of the data for which sea lice species were recorded, just over 96% of samples were identified as Lepeophtheirus salmonis. Logistic regression models assessed the association between the presence of lice and a range of independent variables. These models indicated a significant degree of spatial variation, much of which could be explained in terms of salinity levels. There were also important variations through time, both over the season within a year and across years. In addition, coho salmon were significantly more likely (odds ratio = 1.65; 95% CI = 1.20-2.3) to be infected than chum salmon. The protective effect of low salinity was most clearly seen at values lower than 15 psu, although this was dependent on fish species.

KEY WORDS: Ectoparasite · Lepeophtheirus salmonis · Chum salmon · Vancouver Island · Salinity · Epidemiology · Oncorhynchus

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Cite this article as: Elmoslemany A, Revie CW, Milligan B, Stewardson L, Vanderstichel R (2015) Wild juvenile salmonids in Muchalat Inlet, British Columbia, Canada: factors associated with sea lice prevalence. Dis Aquat Org 117:107-120.

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