Methylmercury levels in commercially harvested spiny dogfish from off the coast of massachusetts

Published on
28. April 2020

Methylmercury levels in commercially harvested spiny dogfish (squalus acanthius) from off the coast of massachusetts

George A. Maynard, Zofia Baumann


Spiny Dogfish are small sharks that are harvested for seafood, primarily off the Eastern Seaboard of the United States. For the purposes of establishing seafood consumption advisories with regards to methylmercury (MeHg) content, the US Food and Drug Administration (FDA) classifies Spiny Dogfish as “sharks”, an overly‐broad taxonomic grouping with a mean MeHg content of 0.98 μg/g (wet weight). Because the FDA mean includes fishes of different species, collected internationally over the last four decades, there is reason to believe that the FDA mean value is not reflective of the fish harvested in the Spiny Dogfish fishery. To evaluate how closely Spiny Dogfish match the values in the FDA’s generic “shark” category, we collected muscle samples from 102 commercially harvested Spiny Dogfish caught off Cape Cod, Massachusetts in the 2018 fishing season. Among the fish we sampled, 100% had MeHg concentrations lower than the FDA “shark” mean, and 77.5% had MeHg concentrations that the FDA considers safe for consumption at a frequency of once per week. The mean MeHg concentration in our samples was 0.378 μg/g (wet weight), less than half of the value for the generic “shark” category. Moreover, through a comparison with data from the 1970s, we document a 30% decline in MeHg concentrations for select size categories of Spiny Dogfish off the coast of New England. Exposure simulations indicate that, to minimize risk, Spiny Dogfish should be consumed no more than twice per month by most people.

Transactions of the American Fisheries Society, DOI:10.1002/tafs.10243


Leave a Reply