Trace elements in grey seals from the Gulf of St. Lawrence

Abstract

We measured baseline levels of 19 trace element and mercury speciation for grey seals (Halichoerus grypus) from the Gulf of St. Lawrence (GSL), Quebec, Canada. With interest growing in commercializing grey seal products for human consumption in this region, the goal of this study was to measure essential and non-essential trace elements in grey seals to evaluate health concerns and nutritional benefits. From 2015 to 2019, 120 grey seals were sampled by hunters and researchers at 4 sites in the GSL. Muscle, liver, heart and kidney samples were analyzed for 10 non-essential elements (Sb, As, Be, B, Cd, Pb, Hg, Ni, Tl, Sn) and 9 essential elements (Co, Cr, Cu, Fe, Mg, Mn, Mo, Se, Zn). Both total mercury (THg) and methylmercury (MeHg) were analysed for a subset of samples. Many elements were undetected in liver (Sb, As, Be, B, Cr, Co, Pb, Ni, Tl, Sn) and muscle tissues (same, plus Cd, Mn, Mo). Results showed lower element concentrations in the muscle (Fe, Mg, Se) and livers (Cd, Cr, Hg, Mn, Mo, Se) of young-of-the-year harvested in the winter (< 6 weeks old) compared to older animals feeding at sea. For older seals (~ 5 months to 29 years), we did not observe progressive age-dependent bioaccumulation. Sex-specific differences were not very pronounced, but a few elements were 30 - 70% higher in the muscle (THg, MeHg) and liver (Mn, Zn) of male seals. Comparison to Canadian dietary reference intakes shows that a weekly portion of liver from young-of-the-year (< 6 weeks old) is a good source of essential elements (Cu, Fe) and that muscle and liver from this age category does not exceed reference values for toxic elements (As, Cd, Pb, MeHg). Ongoing discussions with regional public health professionals will help to develop dietary recommendations for the consumption of older grey seals.