Reducing the reef fish risk

One of the dreams of voyaging is to cut one’s ties with consumer culture and be self-sufficient. And what could be more self-reliant than to catch your supper from the lagoon of some tropical island? While fresh fish is surely one of the great perks of the sailing life, catching and eating a fish in coastal waters is not without a degree of risk. A new product from a Hawaiian company named Oceanit Test Systems of Honolulu (808-539-2345, should lessen that danger considerably.

The risk in eating reef fish comes from a type of poisoning called ciguatera. Voyagers who contract this disease may experience symptoms that range from the annoying to the fatal. Ciguatera toxin infects just about all species of reef fish, and there is no way to tell just by inspection whether a particular fish is tainted. Thoroughly cooking, freezing, smoking, or salting the fish won’t render it less toxic. Even years of local knowledge don’t helpin Hawaii, local fishermen are often struck with ciguatera when they eat their catch.

These unsavory facts are enough to make a voyager put his or her fishing rod away until reaching deep water. No deep-water fishe.g., tuna, marlin, dorado, or wahoohave been found to carry ciguatoxin. However, since marine life is disproportionally concentrated in coastal waters, voyagers are forced to avoid a large stock of potential catch. In Hawaii, for example, reef fish that can carry ciguatoxin include amberjack, jack trevally, mullet, gold-ring or yellow-eyed surgeonfish, parrotfish, gray snapper, eye-striped surgeonfish, eel, and ring-tailed wrasse. Now, however, there’s hope for voyagers who wish to catch fish while in a lagoon or sailing along a coast. A test kit called Cigua-Check enables voyagers to test a small sample of a recently caught fish for ciguatoxin. Oceanit Test Systems, which produces the kit, claims that Cigua-Check is the first reliable, practical test available outside the laboratory for detecting tainted fish. Ciguatera starts with a microscopic dinoflagellate algae called Gambierdiscus toxicus.

This organism, which contains a neurotoxin that affects humans, settles on marine plants in coastal waters, and small plant-eating fish consume both the plants and the algae. Larger fish eat the smaller fish, and the toxin is passed up the food chain, concentrating the toxin with each level. Particularly dangerous are the roe (eggs), liver, and other internal organs where the poison is even more highly concentrated than in the flesh of the fish.

The symptoms of ciguatera are not so distinct that this malady is easy to diagnose. For example, a voyager sick with ciguatera might experience weakness; abdominal cramps; diarrhea; nausea; headache; muscle pain and joint aches; numbness and tingling around the mouth, hands, and feet; and, perhaps most bizarre, temperature reversal (when cold feels hot and hot feels cold). "It’s a tough diagnosis," said Dr. Daniel Carlin, who runs WorldClinic, a telemedicine service for travelers. "And it’s tough for a doctor because there’s no way to treat it, other than symptomatically." One of the important diagnostic clues, of course, is the victim’s recent diet. If reef fish has been consumed, ciguatera is a possible culprit. Other than the fact that it’s possible, although rare, to ingest a sufficiently large dose of the toxin to cause death, one of the most distressing aspects of the disease is its potential longevity. "It can last weeks, months, or even years," said Carlin. The only way to treat ciguatera is to reduce the symptoms using mannitol (an osmotic diuretic that promotes the urinary excretion of toxic substances). But this doesn’t eliminate the disease.

The best approach, of course, is to avoid reef fish altogether. However, according to Oceanit Test Systems, when armed with a Cigua-Check kit it is possible to accurately test for ciguatoxin. The kit contains enough test vials and test strips for five tests. A rice-grain-sized sample is removed from the flesh of a recently caught fish. This piece is then put into a clear vial for 20 minutes. "The vial contains alcohol, which extracts the toxin from the fish tissue," said Dr. Joanne Ebesu, research director at Oceanit Test Systems. A test strip is then put into this solution. On the end of this strip is a membrane to which the lipid-based toxin sticks. The test strip is removed from the vial and allowed to dry for 20 minutes. The test stick is then immersed in a second vial that contains purple polystyrene coated with an antibody to the ciguatoxin. "If there is any toxin on the strip, the purple-colored antibodies stick to it," said Ebescu. The stick is gently rinsed and then compared to a color key on the inside cover of the test box. The darker the strip, the more ciguatoxin present and the more dangerous the fish. Oceanit guarantees a shelf life of six months for an unrefrigerated kit. Keeping the kit in the fridge will extend its life, but the company has no data on how long. "We also include positive and negative control tests so you can check to see if the kit is still working before you test your fish," said Ebesu.

The Cigua-Check is available for $20, or $4 a test. But doing a test isn’t something you would probably start on the spur of the moment, since the process requires a time investment of 70 minutes before you get a result. Still, having Cigua-Check aboard just might save a crewmember from the effects of ciguatera in a deserted anchorage.

By Ocean Navigator