. The Canadian field-naturalist. Natural history. 638 The Canadian Field-Naturalist Vol. 117. smolt-only unexposed Figure 3. Boxplots showing range of lice abundance (left) and number of lice/g host weight (right) by exposure category. The line at the notch represents the median. Whiskers are drawn to x (Inter-Quartile Range). Values beyond this are identified individually by horizontal lines. The skew indicated by these boxplots shows the need for non-parametric analyses. carrying > lice per gram host mass weighed less, on average, than fish of the same length that carried less than
. The Canadian field-naturalist. Natural history. 638 The Canadian Field-Naturalist Vol. 117. smolt-only unexposed Figure 3. Boxplots showing range of lice abundance (left) and number of lice/g host weight (right) by exposure category. The line at the notch represents the median. Whiskers are drawn to x (Inter-Quartile Range). Values beyond this are identified individually by horizontal lines. The skew indicated by these boxplots shows the need for non-parametric analyses. carrying > lice per gram host mass weighed less, on average, than fish of the same length that carried less than lice per gram host mass (Figure 4). Discussion This is the first report of L. salmonis infection on juvenile Pink Salmon. Our data suggest the infection was related to the presence of net-pen salmon farms in the immediate area (Table 1, Figure 3). The rate of infestation almost certainly reduced survivorship of the infected fish by compromising growth (Figure 4). The large percentage of infected fish raises concern for the health of the stock (Table 1). Most research on L. salmonis infestation of juvenile wild salmonids pertains to Sea Trout, Atlantic Salmon and Arctic Charr. Finstad et al. (2000) estimated that juveniles of these species can tolerate up to 10 Sea Lice per fish. Observations on 3000 post-smolt Atlantic Sal- mon, in open oceanic waters from 1991 to present, did not find a single fish with more than 10 adult lice (Hoist et al. 1992*). Among these, fish with close to 10 lice were physiologically compromised (reduced growth and low hematocrit values) (Hoist, personal communication). While wild Atlantic salmonids spend a year or more in fresh-water and the Atlantic Salmon, for example, enters sea water at approximately 30 g (Poole et al. 2003), Pink Salmon go to sea at approximately g (Bailey et al. 1975). Given that experimental results show that young salmonids can tolerate approximately one louse per gram of body weight (Grimnes and Jakobsen 1996; Bj0rn
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