Potential Effects of Contaminants on Fraser River Sockeye Salmon

that is used to manage the use <strong>of</strong> sockeye salmon by commercial fishers, recreationalanglers, and aboriginal groups (i.e., it is not practical to manage each stock <strong>of</strong> sockeyesalmon in the Fraser River independently because they are difficult to distinguish inapproach and riverine fisheries).To address the limitations associated with the stock concept, salmon managers havedeveloped the concept <strong>of</strong> sockeye salmon conservation units to provide a more practicalbasis for managing stocks that originate within a common geographic area. Aconservation unit is defined as “Groups <strong>of</strong> wild salmon living in an area sufficientlyisolated from other groups that, if extirpated, the area is very unlikely to be recolonizednaturally within an acceptable time frame” (Holtby and Ciruna 2007). For Fraser Riversockeye salmon, a total <strong>of</strong> 36 conservation units have been identified, based on data from275 sampling sites in the basin (Table 2.1, 2.2, 2.3, and 2.4; Pestal and Cass 2009). Thesesockeye salmon conservation units were examined to identify key exposure areas (i.e.,termed Areas <strong>of</strong> Interest in this study) for sockeye salmon in the Fraser River Basin.These areas <strong>of</strong> interest describe the geographic scope <strong>of</strong> the study area.2.3 Areas <strong>of</strong> InterestSockeye salmon utilize spawning and rearing habitats throughout much <strong>of</strong> the Fraser RiverBasin. In addition, juvenile and adult sockeye salmon utilize migration corridors withinthe basin. Sockeye salmon can be exposed to aquatic contaminants in spawning habitats,rearing habitats, and/or migration corridors. Therefore, it is necessary to identify keyexposure areas within the Fraser River Basin that are relevant to the various sockeyesalmon conservation units. These exposure areas are referred to as areas <strong>of</strong> interest in thisstudy.In this study, areas <strong>of</strong> interest were identified using information on the distribution <strong>of</strong>sockeye salmon within the Fraser River Basin. More specifically, the sampling sites forearly Stuart, early summer, summer, late, and river-type conservation units (Pestal andCass 2009) were reviewed to identify a total <strong>of</strong> 15 exposure areas within the river basin(Figure 2.3), including:• Lower Fraser River Area <strong>of</strong> Interest (i.e., from river mouth to Hope);• Upper Fraser River Area <strong>of</strong> Interest (i.e., from Hope to Red Pass);9