Salting Reduces Mercury Concentrations in Odontocete Muscle Tissue

Abstract High mercury (Hg) concentrations in seafood present a major global public health concern, especially in regions heavily dependent upon seafood like the Caribbean. Tissues from predatory fishes and other high trophic-level marine organisms such as odontocetes (toothed whales and dolphins) are often elevated in mercury, owing to biomagnification. We investigated whether salting reduces the total mercury (THg) concentration in muscle tissue from odontocetes (“blackfish”) taken for human consumption in St. Vincent and the Grenadines. Muscle from 21 odontocetes was coated in table salt or sea salt and dried for one, three, or seven days, after which the THg concentration in each sample was determined and compared to the THg concentration in the corresponding unsalted control. Every salted sample had a lower THg concentration than the unsalted control (mean decrease = 29.4%). There was no difference in the effectiveness of table salt versus sea salt at reducing the THg concentration. Our results show that, while salting successfully removed Hg, only 11% of samples had a methylmercury (MeHg) concentration below the World Health Organization's 1.0 µg/g wet weight advisory level, indicating that consuming odontocete muscle still poses a risk to human health—though that risk may be reduced by the application of salt during drying. The method that we present here may also be applicable to tissues from other marine species with lower initial THg concentrations and may be effective at rendering those tissues safer for human consumption.