Potential Effects of Contaminants on Fraser River Sockeye Salmon

observed in saltwater gobies (Chasmichthys dolichognethus) that accumulated 0.91mg/kg WW <strong>of</strong> TBT in their tissues (i.e., whole body; Shimizu and Kimura 1987). InJapanese medaka, embryonic development, hatching, and swim-up success weresignificantly affected in fish fed TBT-amended diets (Nakayama and Oshima 2008). Inaddition, mating behaviour and non-sexual behaviours were altered in fish exposed toTBT. All <strong>of</strong> these effects were enhanced when fish were simultaneously exposed toTBT and PCBs in their diet. These data demonstrate the potentially additive effects <strong>of</strong>TBT and PCBs on fish. The available literature also provide evidence <strong>of</strong>transgenerational toxicity <strong>of</strong> TBT. Nirmala et al. (1999) reported decreased survival<strong>of</strong> embryos and larvae <strong>of</strong> Japanese medaka derived from eggs containing 0.279 µg/kgWW <strong>of</strong> TBT spawned by females containing 2.39 mg/kg WW. In Japanese flounder(Paralichthys olivaceus), dietary exposure to TBT (at 0.1 or 1.0 µg TBT/g diet) for100 or 300 days exhibited decreased growth compared to control fish (Shimasaki et al.2003). Importantly, the proportion <strong>of</strong> sex-reversed males was significantly increased,relative to controls, in both treatment groups. After 100-d, the concentrations <strong>of</strong> TBTin the high and low exposure groups averaged about 0.16 mg/kg WW and 0.02 mg/kgWW, respectively. Although the available data are limited, it appears thatreproduction is likely to be adversely affected in fish that accumulate more than 0.02mg/kg WW <strong>of</strong> TBT in their tissues. This toxicity threshold is likely to be lower whenTBT occurs in fish tissues along with other endocrine disrupting compounds, such asPCBs.Other Metals - The data available to evaluate the endocrine disruption effects <strong>of</strong> othermetals (i.e., beyond MeHg and TBT) are limited. However, Thomas (1988) reportedcadmium enhanced vitellogenesis in Atlantic croaker exposed to 1 mg/L for 30 days.In rainbow trout, exposure to 10 or 25 µg/L <strong>of</strong> cadmium decreased the concentrations<strong>of</strong> two thyroid hormones (triiodothyronine and thyroxine, which are important foradapting to changes in environmental conditions; e.g., salinity) in plasma and increasedplasma cortisol levels (which is involved in stress response; Ricard et al. 1998).Rainbow trout exposed to lead at 10 µg/L for 12 days had lower gonadosomatic indexscores and smaller oocytes than control fish, indicating an effect on the pituitary gland(Ruby et al. 2000). Thomas (1988) also reported lower gonadosomatic index scoresfor Atlantic croakers exposed to lead in their diets (1.34 mg/70g fish/day) for 30 days.Biogenic Compounds - Plant sterols and phytoestrogens are naturally occurringsubstances that can act as endocrine disruptors when released into the environment.Incomplete information is available to evaluate effects on fish associated with exposureto naturally-occurring phytosterols and/or phytoestrogens. However, MacLatchy et94