Potential Effects of Contaminants on Fraser River Sockeye Salmon

$ Early rearing <strong>of</strong> sockeye salmon fry in nursery lakes (April 1 toMarch 31);$ Downstream migration <strong>of</strong> sockeye salmon smolts through riverine(i.e., Fraser River and tributaries) and estuarine habitats (May 1 toJune 30); and,$ Upstream migration <strong>of</strong> sockeye salmon adults through estuarineand riverine (i.e., Fraser River and tributaries) habitats (June 1 toSeptember 30).Surface water chemistry data, which were collected during the listed exposure periods,were extracted from the project database and used in all further analyses. Thepreliminary evaluation <strong>of</strong> chemicals <strong>of</strong> potential concern and the evaluation <strong>of</strong>contaminants <strong>of</strong> concern were performed using the surface water quality data for eacharea <strong>of</strong> interest. Due to limitations in the available sediment quality data, these datawere not further categorized according to exposure periods.In addition, the assessment <strong>of</strong> the environmental data was conducted for two distincthistorical time periods: prior to and including 1990 (i.e., pre-1990); and, 1991 up to andincluding 2010 (i.e., post-1990), where data were available. The separation <strong>of</strong> theenvironmental data into these two time periods facilitated the evaluation <strong>of</strong>environmental quality conditions during two distinct trend periods in sockeye salmonproductivity observed over the last 50 years.A4.3.2 Calculation <strong>of</strong> the Water Quality IndexThe CCME Water Quality Index provides a consistent basis for evaluating theproportion <strong>of</strong> toxicity screening values exceeded, the frequency <strong>of</strong> exceedance <strong>of</strong> thetoxicity screening values and the magnitude <strong>of</strong> exceedance. Accordingly, the WaterQuality Index provides a convenient tool for comparing water quality conditions acrossgeographic areas and time periods (CCME 2001; Saffran et al. 2001).Water quality data for the index calculation were grouped by three factors: year,exposure period (e.g., rearing), and salmon stock (e.g., Birkenhead stock). Inaddition, the index period was adjusted to reflect the actual exposure period for eachbrood year as follows:$ Water quality data collected during the brood year were used tocalculate the index during the spawning exposure period;$ Water quality data collected one year after the brood year wereused to calculate the index during the rearing exposure period;$ Water quality data collected two years after the brood year wereused to calculate the index during the outmigration exposureperiod; and,A-34