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May 05, 2011

The Perils of Ciguatera

Will your next fresh-caught fish dinner be a toxic time bomb?

Deadly Plankton
ciguateraThe ailment's name doesn't explain much but reveals that this nasty fish poisoning has been around for a long time. Spanish explorers who described it very clearly in the 1500s attributed it to a small snail they called the cigua.

What actually causes ciguatera is far smaller and more insidious than a snail. A type of plankton, appropriately named Gambiendiscus toxicus, produces ciguatoxin. G. toxicus is fond of attaching itself to marine algae on coral reefs. Small fish that eat the algae accumulate the fat-soluble toxin. As larger predators eat these herbivores and are in turn eaten by still larger fish (you know, the size you like to throw in your fish box), concentrations of the toxin - which, by the way, affect only mammals - increase geometrically.

Such fish become time bombs for people unlucky enough to eat them.

Beware the Reef's Biggest and Baddest
Given the source of this toxin, anglers have little reason for concern with any cold-water game fish nor, for the most part (though not always), with open-ocean pelagics. The association of Gambiendiscus with coral reefs makes it common in tropical fish. A wide range of species that inhabit tropical reefs and/or eat reef fish can concentrate enough ciguatoxin to be a danger.

A host of well-established bad actors frequently ­implicated in ciguatera poisonings include amberjack, hogfish (a type of wrasse), cubera and mutton snappers, many other jacks such as black jacks and giant trevally, and many species of grouper - including the widespread coral trout that nailed Pepperell, and particularly the lovely Caribbean yellowfin grouper (note its scientific name, Mycteroperca venenosa, the latter meaning "poisonous"). But the list is long and also includes king mackerel, triggerfishes, wrasses, parrotfishes and dozens of others.

Most notoriously associated with ciguatera by those who live in tropical waters would have to be the great barracuda and red bass. The latter is one of the most common members of the snapper family around much of Australia and the Indo-Pacific, a very aggressive shallow-reef-loving fish widely sought by anglers.

Russian Roulette
If fish eaters who live in the tropics lack knowledge about ciguatera, those who live far inland know even less. It's unlikely that dozens of diners ever heard of the disease when they indulged in tasty dinners of fresh Gulf of Mexico amberjack in various St. Louis eateries in December 2007. They know about it now, having found out the hard way, with many hospitalized after a typical incubation period as short as 10 minutes or as much as days after ingestion.

ciguatera kitConsumers in Canada learned of ciguatera earlier this year when the Canadian Food Inspection Agency warned the public against consuming a brand of leatherjacket - a large species of smooth puffer - imported from China after ciguatera reared its ugly head, victimizing at least two diners.

Eating amberjack or, in fact, any of these fish, even large barracuda or snapper, does not mean you're doomed to come down with the disease. Far from it: Around the world, people eat these fish every day with no problem.

On the other hand, one can't entirely rule it out in many instances, and therein lies the rub. It's like Russian roulette, albeit with one bullet in a clip that can hold thousands of rounds, not just six. Still, it's one bullet you don't want to bite.

Ciguatoxin is particularly treacherous in a number of respects. For one thing, it's heat stable, so cooking doesn't faze it. Nor is it bothered by freezing. In other words, if it's in a fish's flesh, nothing you can do will get rid of it.

Here's more treachery: The toxin has no effect on the fish's flesh. You can neither smell nor taste it. In short, it's pretty much undetectable.

Reducing Your Odds
Never eating any fish that live in or around coral reefs would probably assure you of avoiding ciguatera, though such a step is a bit drastic. But you can reduce the odds even further in your favor that your favorite fish, whether caught or bought, won't prove host to the toxin.

Consider the size. The larger the reef fish, the more likely it is to be ciguatoxic. That makes sense since the toxin concentrates, like mercury, as it moves up the food chain. I've heard various rules of thumb - e.g., any fish less than 5 pounds is safe and some no more than 2 pounds. There is no hard-and-fast rule, but it's empirically evident that larger fish generally account for outbreaks. (The owner of one of the St. Louis restaurants serving meals unaware from a ciguatoxic 60-pound AJ told a newspaper reporter he now understood big fish could be problematic, so he wouldn't serve any amberjack exceeding 25 pounds in the future. In fact, that arbitrary cutoff probably means little.) As an angler, you have the opportunity to throw back larger predators if you wish (unlike diners, who have no way of knowing how large a fish provided the fillets on their plate).

Consider where and when caught. Some areas are hotbeds for G. toxicus. Often this is well known locally. For example, Ray Waldner, Ph.D., a fisheries biologist with Florida's Palm Beach Atlantic University, cites Cuba (especially for hogfish) and the Dry Tortugas in the Caribbean. Fish from Bahamas reefs have been implicated over the years as well. Yet there are many tropical regions where the disease remains virtually unknown. But just to complicate matters, reef areas apparently historically free from ciguatera can become "infected" at any time, while those infected can later become ciguatera free.