Mercury and methylmercury distribution in tissues of sculpins from the Bering Sea

Fish skeletal muscle is often used to monitor mercury concentrations and is used by regulatory agencies to develop fish consumption advisories. However, the distribution of mercury species (MeHg+ and THg) in muscle tissue and other organs is not well understood in a number of fish species. Here we evaluate the spatial distribution of THg and MeHg+ in skeletal muscle and internal organs (heart, liver, and kidney) of 19 sculpin representing three species: Myoxocephalus scorpius (shorthorn sculpin n = 13), Myoxocephalus jaok (plain sculpin, n = 4), and Megalocottus platycephalus (belligerent sculpin, n = 2). Four subsamples of muscle were taken along the lateral aspect of each fish, from muscle A (cranial) to muscle D (caudal). Using Games–Howell post hoc procedure to compare mean concentrations of all tissues, muscle samples were significantly different from internal organs, although there was no difference between muscle-sampling locations. THg concentrations (ww) were higher in muscle (muscle A through D mean ± SD, 0.30 ± 0.19 mg/kg) than that in heart (0.06 ± 0.05 mg/kg), kidney (0.08 ± 0.06 mg/kg), and liver (0.09 ± 0.08 mg/kg). Percent MeHg+ decreased with age in both skeletal muscle and organs (p < 0.05). In contrast to some previous reports for other fish species, this study found significantly higher THg concentrations in muscle than in the liver. This study highlights the importance of using muscle samples when evaluating potential Hg exposure in risk assessments for piscivorous wildlife and human populations, and assumptions related to organ mercury concentrations should be examined with care.