Mercury concentrations in muscle tissue from sportfish in Lake Mead, Nevada

The aim of this study was to determine the concentrations of mercury present in commonly consumed fish from Lake Mead and to identify if differences exist between the 4 major basins. To date, no formal study using US Environmental Protection Agency (USEPA) approved methodology has been conducted to quantify the amount of mercury present in fish tissue from Lake Mead. Largemouth bass (n = 49), striped bass (n = 94) and channel catfish (n = 78) were collected from selected sites in Boulder Basin, Overton Arm, Virgin Basin and Gregg Basin of Lake Mead. Muscle tissue was homogenized, digested and analyzed for mercury in accordance with USEPA Method 245.6. Mean total mercury concentrations were (± SD) 0.089 ± 0.065, 0.154 ± 0.127 and 0.098 ± 0.080 μg/g in largemouth bass, striped bass and channel catfish, respectively. There was a significant overall difference in mean mercury concentration between fish from the 4 major basins of Lake Mead (F3,208= 20.541, p \u3c 0.001). The mean mercury concentration in Boulder Basin was significantly lower than all other locations (p \u3c 0.001). Of 221 samples analyzed, 10 samples were found to have mean mercury concentrations above the USEPA\u27s 2001 tissue residue criterion of 0.3 μg methlymercury/g fish tissue