In the midst of a celebratory fishing tournament off the Hull Bay shore, a team of volunteers worked quietly to search for the cause of a known disease. This disease, ciguatera, is well known to many Virgin Islanders who enjoy digging in the catch of the day.
UVI volunteers collect fish samples at tournament in Hull Bay (Photo by Judi Shimel)
A guest researcher working with local volunteers said they set up a sampling station for fish donated by anglers who participated in the recent Bastille Day Kingfish Tournament. Sunday, July 10th was the third St. Thomas sportfish survey for graduate student Jesse Gwinn of the University of South Alabama. She said the work is part of a decade-long study being conducted in collaboration with the University of the Virgin Islands.
Ciguatera — also called fish poisoning — is a debilitating but temporary illness contracted by people who eat contaminated fish. Gwinn says the Northside Fishing Tournament gives researchers the opportunity to study barracuda, kingfish and Spanish mackerel that swim in waters considered a ciguatera hotspot.
“The idea is that the fishermen will check in their fish, hang them on the board of nails and take pictures with their fish, and we’ll ask them if they donate their fish,” Gwinn said. “If they don’t want them, we’re happy to take them and sample them for some muscles, gonads and liver so we can use them to extract the toxins and study them.”
Donated fish were then placed over a workbench where volunteers cut out samples of muscle, gills and sex organs. Samples are tagged, bagged and charted before being stored in ice chests. Extensive sampling allows investigators to find out if more than one species of contaminated algae thought to be the source are found throughout the sample.
The principal investigator of the UVI study is coral reef researcher Tyler Smith. He said efforts to track ciguatoxins have been ongoing since 2007. Collaboration with Alison Robertson, Smith’s colleague at the University of South Alabama, came later.
“We have been working together since 2007, with initial work being done with Woods Hold (Oceanographic Institute in Massachusetts). It really blossomed from there,” Smith said. “The study we have is quite extensive. We really care about the whole environment and look at which algae produce ciguatoxin. Just finding these microalgae cells and identifying what species they are is not easy.”
Scientists believe that human exposure to ciguatoxin occurs along a food chain; Fish eat poisonous algae and humans eat the fish. One of the reasons St. Thomas could be considered a Ciguatera hotspot emerged from a 2019 UVI-UAS sampling.
“At least as of 2019, at least 98 percent of the fish we tested were venomous. I’m not sure of the exact levels … I’m not sure how many of them were unsafe to eat, but we were able to detect ciguatoxins in 98 percent of them,” she said.
Smith added that he recognized the efforts of local fishermen to keep the fish species most at risk of fish poisoning away from consumers. “It helps put our program in a good light with the fishing community,” he said.
And while that’s not the primary focus, Gwinn says, the researchers are also studying the effects of climate change on ciguatera distribution. Toxic algae have been discovered on oil rigs in the Gulf of Mexico, she said.
Smith said a northerly migration from warmer waters where ciguatoxin can thrive isn’t the only reason cases of fish poisoning are popping up in places never seen before. “The human side is that people move, and when they move, they take with them the foods they are used to. And so some of these ciguatoxins are showing up in places they’ve never been before, in people who don’t know about them,” Smith said.
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