Effects of dietary methylmercury on juvenile Sacramento blackfish bioenergetics

• Published in: Aquatic toxicology Vol. 69; no. 2; pp. 107 - 123
• Main Authors: Houck, Ann, Cech, Joseph J
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 10.08.2004; Elsevier Science
• Subjects: Agnatha. Pisces; Analysis of Variance; Animal, plant and microbial ecology; Animals; Applied ecology; Bioaccumulation; Biological and medical sciences; California; Cyprinidae; Cyprinidae - growth & development; Cyprinidae - metabolism; Dose-Response Relationship, Drug; Eating - drug effects; Ecotoxicology, biological effects of pollution; Effects of pollution and side effects of pesticides on vertebrates; Energy Metabolism - drug effects; Fish bioenergetics; Fresh Water; Freshwater; Fundamental and applied biological sciences. Psychology; MeHg assimilation; Methylmercury (MeHg); Methylmercury Compounds - pharmacokinetics; Methylmercury Compounds - toxicity; Muscle, Skeletal - metabolism; Orthodon microlepidotus; Oxygen Consumption - drug effects; Spectrophotometry, Atomic; Time Factors; Toxicity Tests, Chronic; California; United States; North America; America; USA, California, Clear L; USA, California, Sacramento; Fish bioenergetics; Bioaccumulation; Methylmercury (MeHg); MeHg assimilation; Freshwater environment; Aquatic environment; Vertebrata; Ecotoxicology; Toxicity; Pisces; Lakes; Cyprinidae; Biological accumulation; Young animal; Organic compounds; Feeding
• ISSN: 0166-445X; 1879-1514
• DOI: 10.1016/j.aquatox.2004.04.005

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 ( r 2=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.