Mercury concentrations in edible muscle of Lake Whatcom Fish

Abstract Concentrations of total mercury were assessed in edible muscle (fillet) tissues of 273 fish collected from Lake Whatcom near Bellingham, Washington. Samples of six finfish species and signal crayfish were analyzed from each of the lake?s three major basins. Mercury concentrations were much higher in smallmouth bass (Micropterus dolomieu) compared to yellow perch (Perca flavescens), kokanee (Oncorhynchus nerka), pumpkinseed (Lepomis gibbosus), cutthroat trout (Oncorhynchus clarki), brown bullhead (Ameiurus nebulosus), and signal crayfish (Pacifastacus leniusculus). Concentrations were positively correlated with length and age in smallmouth bass, and to a lesser extent in yellow perch and Basin 2 signal crayfish, but no such relationship was seen in other species. The overall mercury concentration in smallmouth bass averaged 0.49 µg/g (wet weight), and the maximum concentration was 1.84 µg/g. Mean mercury concentrations in other species were generally 0.05 ? 0.20 µg/g. All species from the southern Basin 3 had more mercury on average compared to their counterparts from the northern Basins 1 and 2, regardless of average size or age. However, there was no consistent direction in mercury concentrations between samples from Basin 1 and Basin 2. The Washington State Department of Health will use these data to develop a health risk assessment for Lake Whatcom, as a separate document. The Washington Department of Fish and Wildlife will assess the potential impact of mercury on fish health, also as a separate document. Since 13 of the samples exceeded the EPA National Toxics Rule human health criterion of 0.825 µg/g, the Washington State Department of Ecology should add Lake Whatcom to the Section 303(d) list for mercury in tissue. Other recommendations are to investigate possible mercury sources to Lake Whatcom and determine if lake or watershed characteristics promote enhanced mercury uptake and accumulation by fish.