The sport fishing bounty also gives research harvest

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In the midst of a festive fishing derby on the shores of Hull Bay, a team of volunteers worked quietly to find the cause of a well-known ailment. This disease, ciguatera, is known to many Virgin Islanders who like to dive into the catch of the day.

UVI volunteers extract fish samples during the Hull Bay tournament (photo by Judi Shimel)

A visiting researcher, working with local volunteers, said he set up a sampling station for fish donated by anglers taking part in the recent Kingfish tournament on July 14. Sunday, July 10 was the third St. Thomas Sport Fish Survey for University of South Alabama graduate student Jesse Gwinn. She said the work was part of a decades-long study conducted in conjunction with the University of the Virgin Islands.

Ciguatera – also called fish poisoning – is a debilitating but temporary disease contracted by those who eat contaminated fish. Gwinn says the Northside Fishing Tournament gives researchers a chance to study barracuda, trevally and Spanish mackerel swimming in waters considered a ciguatera hotspot.

“The idea is for anglers to log their fish, post them on the nailboard and take pictures with their fish, and we’ll ask them if they’ll donate their fish,” Gwinn said. “If they don’t want them, we gladly take them and harvest them for a bunch of muscle, gonads and livers, so we can use them to extract the toxins and study them.”

The donated fish were then placed on a work table where volunteers cut up samples of muscle, gills and sex organs. Samples are labelled, bagged and recorded on cards before being stored in coolers. Thorough sampling allows investigators to determine if more than one type of contaminated algae, thought to be the source, is in the sample.

The UVI principal investigator in the study is coral reef researcher Tyler Smith. He said efforts to track ciguatoxins had been ongoing since 2007. Collaboration with Alison Robertson, Smith’s counterpart at the University of South Alabama, came later.

“We have been working since 2007, with early work being done with Woods Hold (Massachusetts Institute of Oceanography). From there, it’s really blossomed,” Smith said. “The study we have is quite sprawling. We’re really looking at the whole environment, looking at what algae produce ciguatoxin. It is not easy to find these microalgae cells and identify which species.

Scientists believe that human exposure to ciguatoxin follows a food chain; the fish eat toxic algae and humans, in turn, eat the fish. One of the reasons St. Thomas could be considered a ciguatera hotspot came during a UVI-UAS sampling session in 2019.

“At least as of the year 2019, at least 98% of the fish we tested were toxic. I’m not sure of the exact levels…I don’t know how many of them were unsafe to eat, but we were able to detect ciguatoxins in 98% of them,” she said.

Smith added that he appreciates the efforts of local fishermen to keep the types of fish that pose the greatest risk of fish poisoning away from consumers. “It helps keep our program in a good light with the fishing community,” he said.

And while that’s not the main focus, Gwinn said researchers are also looking at the effects of climate change on the spread of ciguatera. Toxic algae have been detected on oil rigs in the Gulf of Mexico, she said.

Smith said a northward migration of warmer waters where ciguatoxin can thrive isn’t the only reason fish poisoning cases are showing up in places they’ve never been seen before. previously. “The human side is that people move, and when they move, they take with them the foods they are used to eating. And so some of these ciguatoxins are showing up in places they’ve never been before, among people who don’t know anything about it,” Smith said.

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