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Ciguatera: Beware of Fish that Eat Brass

A couple of years ago I was sitting in one of my favorite haunts early one morning after a dive eating canned fruit cocktail pancakes and playing dollar bill poker when one of the down-islander patrons began talking about “fish poisoning.”  According to him, one need not worry about becoming a victim of fish poisoning so long as one does not eat fish that feed upon the brass falling off all the yachts plying our Caribbean waters. 

It did occur to me at the time that I’d not seen much brass lying on the bottom and I did bring up that point, but the down islander countered that I didn’t see brass because fish ate it.  I didn’t bother to mention that I’d cleaned or necropsied hundreds of fish over the years and never found any sort of metal in their digestive tracts for fear he’d tell me brass was quickly digested by the fish leaving no visible traces behind, only brass-filled flesh that would make us unsuspecting consumers seriously ill.

As he continued to impart his knowledge of “fish poisoning,” aka ciguatera, he gave those of us listening a couple of tips on how to avoid the disease.  Always cook fish with fresh coconut meat, said he.  In the absence fresh coconut meat, put a piece of sterling silver in the pot with the fish.  If the coconut turns green or the silver tarnishes, throw out the fish because it carries ciguatera. Or, watch the bugs once you get home with your fish.  If the flies don’t land on the fish, the roaches don’t try to eat it, and ants don’t crawl on it, the fish is poison and should be discarded.

Since then, I’ve found several more tips for avoiding fish poisoning;  all myths, of course, but still adhered to by many, not only throughout the Caribbean, but also in the ciguatera belt around the world.  There’s…feed a piece of the fish to another animal before eating it one’s self and watch the animal for abnormal behavior.  Also, hold the fish’s liver to one’s lips.  If the lips tingle, the fish is poison.  Lay a piece of copper on the raw fish flesh and watch for the copper to turn green.  Green indicates a poison fish.  And, hold a slice of the fish’s flesh towards the sun.  Rainbow coloring on the flesh indicates bad fish.

None of these tips work, they’re all myths!  Brass-eating fish are not the cause of ciguatera; nor is there a method at this point in time for testing a fish as tens of thousands fall victim to ciguatera each year with many thousands more cases going unreported.  There are test kits available from fishing supply purveyors, drug stores, yachting suppliers, and markets but they do not assure a fish is safe to eat and are basically ineffective, giving a false sense of security.

I recently was privileged to attend a private lecture on ciguatera presented by a scientist from Woods Hole Oceanographic Institute, a world renowned oceanic, engineering, and educational research facility in Massachusetts.  Not long before that lecture, one of the scientist’s relatives was fishing off the Florida Keys.  The charter boat captain had a widely available ciguatera testing kit onboard and tested the barracuda they’d caught. The tests results were negative for ciguatera so the barracuda was consumed that evening.  Very early the next morning, the scientist’s relative was admitted to the hospital in serious condition….suffering from ciguatera.

This article and the one to follow next month are not designed to create panic amongst consumers of fish.  While fish stocks around the world are in trouble, the consumption of fish sustains many indigenous populations and is both a delicacy and generally quite a healthy food source.  However, consuming fish should be undertaken with proper knowledge.

All fish are not equal on the scale of safe consumption and while there are no guarantees that proper knowledge will keep us safe from ciguatera, knowing what fish we’re eating, where it comes from, and even the time of year it was caught can certainly save many of us from needless suffering and, in some cases, death.

What is ciguatera?  The most common marine toxin disease.  Fish poisoning, or ciguatera, is a food-borne illness resulting from eating fish flesh containing ciguatoxin.  Ciguatoxin is a neurotoxic (nervous system) poison which affects the body similarly to the neurotoxic venom of snakes such as Coral snakes, Kraits and sea snakes, Mambas, and Cobras.

According to the current Woods Hole research, 73-100% of those ingesting ciguatoxic fish become ill within a few hours.  Signs and symptoms of ciguatera involve neurological, gastrointestinal and cardiac symptoms with severe pain, blurred vision, cardiac arrhythmias and blockage, and, in some instances, temperature reversal, i.e., hot feels cold and cold feels hot, diarrhea, cramping, and vomiting.

Depending upon geographic location, fatality rates can be as high as 12%.  Once the acute phase of ciguatera poisoning abates, some symptoms can last for months and in rare cases years, particularly neurological symptoms and pain.

I remember my father suddenly becoming ill and lying on an embankment beside a road during a trip from Ohio to Florida around 1960.  He was in excruciating pain, vomiting profusely, complaining of numbness, and so weak we had to help him from the car.  When we tried to give him something cold to drink he swore we’d given him something hot.  Not until I attended the lecture on ciguatera did I realize that he was suffering the after effects of ciguatera…fish poisoning he contracted in northern Brazil in the 1940’s.  He was one of those rare cases where the symptoms reoccurred many times.

Next month we will cover how and where fish become ciguatoxic and the measures readers can take to greatly lessen their chances of contracting ciguatera, including a listing of the most common carriers of the disease. 

After 30 years as a wild and domestic animal rescuer, rehabber, and educator in the states, Becky Dayhuff became a scuba instructor and award-winning journalist covering the marine environment in the Caribbean.  She is a contributing photographer to NOAA.

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