Title: Effects of dietary methylmercury on juvenile Sacramento blackfish bioenergetics
Abstract: Although much is known about the biogeochemical cycling of mercury in the environment, relatively little is known about methylmercury (MeHg) bioaccumulation in fishes and how chronic sub-lethal exposures affect their functioning. Several species of fish in Clear Lake, California have high MeHg tissue levels, including Sacramento blackfish, Orthodon microlepidotus, a large native cyprinid that is fished commercially. We fed juvenile blackfish one of four diets containing MeHg (0.21 mg/kg control; 0.52 mg/kg low; 22.2 mg/kg medium; and 55.5 mg/kg high treatments) for 70 days. There were no statistical differences (P>0.05) in food consumption among the treatment groups. By 35 days the high treatment group had a significantly depressed growth rate when compared to the control group (P<0.05) and by 70 days both the medium and the high groups had significantly lower growth rates (P<0.05). The high-dose group had a significantly (P<0.05) lower specific growth rate (SGR) compared all other treatment groups at 35 days, although by 70 days these differences were not significant. The wet/dry muscle mass and muscle mass/total mass ratios, condition factor, and resting routine metabolic rates at both 35 and 70 days were statistically indistinguishable (P>0.05) between treatment groups. All treatment groups assimilated the dietary MeHg into muscle tissue in a dose-dependent fashion. Percent assimilation was significantly lower (P<0.05) in the high-dose group compared to the low-dose group at 35 days, (control 53%, low-dose 61%, medium-dose 50%, and high-dose 40%) but at 70 days assimilation was lower (35, 43, 42, and 32%, respectively) and statistically indistinguishable (P>0.05) among the treatment groups. Dietary MeHg concentrations and bioaccumulation rates were correlated (r2=0.98 at 35 days, 0.99 at 70 days). These results may contribute to construction of ecosystem mercury models and more informed natural resources management at Clear Lake.
Publication Year: 2004
Publication Date: 2004-08-01
Language: en
Type: article
Indexed In: ['crossref', 'pubmed']
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Cited By Count: 50
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