Bioaccumulation of dietary Methylmercury in juvenile Beluga (Huso huso)

Mercury is a unique element that, unlike many metals, has no essential biological function. Wide variety of physiological, reproductive and biochemical abnormalities have been reported in fish exposed, but relatively little is known about methylmercury (MeHg) bioaccumulation in fishes and how chronic sublethal exposures affect their functioning. Objective of this study was to investigate the assimilation and bioaccumulation of dietary methylmercury (MeHg) in juvenile Beluga, Huso huso, a commercially important endangered species in the Caspian Sea. In this study four groups of Beluga juveniles were exposed to four dietary treatments with MeHg: 1- Control group (0.04 mg/kg) 2- Low dose group (0.76 mg/kg) 3- Medium dose group (7.8 mg/kg) 4- High dose group (16.22 mg/kg) for a period of 70 days. Results showed that MeHg accumulation was linear during 70 days and in muscle (P< 0.05) it was significantly higher in the first 35 days. MeHg bioaccumulation in all treatment groups indicated direct relationship with high dependency between dietary MeHg and MeHg accumulation in muscle (R2=0.0973). Percent assimilation was not significant (P> 0.05) among the treatment groups during first and second 35 days, but was higher than second 35 days. It was 57-67% during first 35 days and 42-45% during second 35 days. The results suggested that Mercury contamination could have harmful effects on Beluga even in early years as no exit or transportation for the pollutants exists in the Caspian Sea. The pollutants entering the Caspian Sea through the rivers accumulate in the environment, and a higher amount of them would penetrate into the fish body.