Potential Effects of Contaminants on Fraser River Sockeye Salmon

competitive binding <strong>of</strong> the PAH with the estrogen receptor. In Atlantic croakers(Micropogonias undulatus), dietary exposure to benzo(a)pyrene (BAP; 0.4 mg/70gfish/day) for 30-d during seasonal maturation significantly impaired ovariandevelopment compared to the control treatment (Thomas 1988). The associatedgonadosomatic index scores for the BAP group were about 66% <strong>of</strong> those for thecontrol group. Fathead minnows treated with anthracene had lower reproductiveoutput (as measured by mean number <strong>of</strong> eggs laid) compared to control fish (TilghmanHall and Oris 1991). Collectively, these results demonstrate the potential forendocrine disruption in fish exposed to PAHs, but are insufficient to support selection<strong>of</strong> toxicity thresholds for PAHs in water, sediment, or fish tissues that are directlyrelevant for evaluating endocrine disruption effects on Fraser River sockeye salmon.Polychlorinated biphenyls (PCBs) - Due to their chemical characteristics, PCBs tend tobe highly lipophillic. As such, they tend to accumulate to biological tissues whenreleased into the environment. Accumulation <strong>of</strong> PCBs in fish tissues can result inreproductive and/or developmental effects. For example, Bengtsson (1980) reportedthat minnows, Phoxinus phoxinus, that accumulated 15 mg/kg WW <strong>of</strong> Clophen A50experienced delayed and reduced spawning. In addition to the effects on spawning,reduced egg hatchability was also observed in minnows that accumulated 170 mg/kgWW <strong>of</strong> PCBs (as Aroclor 1254) in their tissues. Similarly, fathead minnows,Pimephales promelas, that accumulated 13.7 mg/kg WW in their tissues wereobserved to spawn less frequently and produce fewer eggs than the control group(USACE 1988). Orn et al. (1998) reported that zebrafish that accumulated 2.7 mg/kgWW <strong>of</strong> total PCBs in their tissues had impaired reproduction relative to control fish(i.e., ovary weight was decreased by about 80%). In salmonids, increased sensitivityto toxic chemicals and decreased growth were observed in trout (Salvelinus sp.)and/or charr (Salmo sp.) that accumulated 0.28 to 1.1 mg/kg WW <strong>of</strong> PCBs in theirtissues (Bills et al. 1981; Bills and Marking 1977; Fisher et al. 1994). Matta et al.(1998) reported that rainbow trout accumulating 2.1 mg/kg WW <strong>of</strong> Aroclor 1260 intheir tissues had increased incidence <strong>of</strong> abnormal gonads compared to control fish.More recently, Meador et al. (2002) conducted a review <strong>of</strong> the scientific literature toestablish a residue effect threshold for salmonid fishes. The results <strong>of</strong> this investigationindicated that a total <strong>of</strong> 15 studies met the evaluation criteria established by theauthors. The lowest observed effect concentration <strong>of</strong> PCBs ranged from 0.11 to 250mg/kg WW in these studies. The tissue concentration that corresponded to the 10 thpercentile <strong>of</strong> the lowest observed effect concentrations, 0.14 mg/kg WW (2.4 mg/kglipid), was selected as the residue effect threshold for salmonid fishes. The median <strong>of</strong>87