By Erin Weeks for The Island Connection
Eating local, sustainably caught fish is a priority for many South Carolinians who want to be healthy and support the coastal economy. But eating fish is not without potential risks – fish consumption represents the greatest source of mercury exposure for Americans, which can present serious health risks at high concentrations.
After a recent study by the South Carolina Department of Natural Resources and the South Carolina Department of Health and Environmental Control, fans of at least one type of fish familiar to local menus can continue to enjoy it.
An analysis of mercury concentrations in blueline and golden tilefish falls in a safe range for weekly consumption.
“Lower mercury levels in tilefish from the Carolinas is good news for consumers as well as the fishermen harvesting them,” said South Carolina Department of Natural Resources biologist Byron White, who led the study.
Tilefish are a group of colorful oceandwellers whose sweet white meat makes them a popular commercial target.
Historically, tilefish have ranked among the top five fish in high mercury levels, a scientific mystery because the bottomdwelling tilefish has a dramatically different life history and behavior than the other high-ranking fish –swordfish, sharks and mackerel.
The high mercury levels in tilefish led U.S. health officials to repeatedly issue advisories against eating them. Those advisories, however, were based on a limited sample: a small number of fish taken in 1978 from the Gulf of Mexico, which is known to have differing levels of mercury in some species when compared with the Atlantic Ocean.
“Part of my interest in doing this study was that perhaps the mercury concentrations in tilefish found off of South Carolina don’t look like those in the Gulf of Mexico,” White said.
For a long time, the Gulf samples were the best available data. Commercial fishermen in New England had their own tilefish samples analyzed, which showed mercury levels vastly lower than those in the Gulf. Those findings prompted the Environmental Protection Agency to specify Gulf of Mexico tilefish as a “choice to avoid” and Atlantic tilefish as a “good choice.”
SCDNR biologists, however, still wondered about the mercury levels of fish taken from local waters.
SCDNR’s long-running Reef Fish Survey, which tracks the health and habitat of offshore reef fish, routinely catches tilefish on its research expeditions.
When the survey team received a grant to learn more about the life history of tilefish, White saw an opportunity to study mercury concentration in the South Carolina fish as well. For two seasons, biologists collected muscle samples from the tilefish they caught.
The researchers also asked McClellanville-based commercial fisherman Steve Shelly if he’d be willing to donate tilefish samples for mercury concentration testing. Shelly, a longtime SCDNR collaborator, was happy to oblige.
For the mercury concentration testing of the tilefish, SCDNR turned to another state agency, SCDHEC, which is responsible for setting guidelines for safe fish consumption in South Carolina. Their findings in 2012 led the health agency to adjust its own fish consumption advisories to recommend one meal per week of tilefish – but it would be years before the team was able to publish their results in a peer-reviewed scientific journal.
The data from this collaborative effort fueled further research, prompting SCDNR biologist Wiley Sinkus – then a student in the College of Charleston’s graduate program in marine biology working with advisor Dr. Virginia Shervette – to look at mercury in several other commercially and recreationally important offshore reef fish in the Atlantic Ocean.
Of the 63 golden tilefish samples collected, 95% fell within the EPA’s “good choices” range, which allows for at least one serving per week. 62% of the samples fell within the range that is considered safe for up to two servings per week. For blueline tilefish, 68% of 62 fish sampled tested within the EPA’s “good choices” category.
“I think it’s important for consumers to know that our samples for this part of the world are considered ‘good choices’ under current EPA guidelines,” White said.