Monday, April 28, 2014

Poisoned seas produce fatal fish

Go into any restaurant in Florida and you will see grouper at the top of the menu. Grouper are tropical reef fish that thrive in the waters of the Gulf of Mexico. The most famous and largest member of the grouper family is the goliath grouper, a huge, slow-moving behemoth of the deep that scares almost no one. Many groupers tip the scales at more than 700 pounds.

An apex predator is one that lives at the top of the food chain, consuming all those below it in the chain. Much of its diet consists of less-than-apex predators. For a long time it has been assumed that the goliath grouper, because of its size, must be one of the sea's apex predators, along with the shark, the dolphin, and the human. But no more.

Studies have shown that the goliath is too slow to do much besides steal fishermen's bait and feast on other critters that scurry along the bottom of the sea. Florida's fishermen are incensed by this pilferage, partly because goliaths have been protected by law since 1990. The fishermen complain that goliaths are responsible for the reduction in lobster populations and are lobbying hard to end the outright ban on goliath fishing.

Sport fishermen frequently claim that "fighting" fish are more exciting to catch. Their desire to catch goliaths seems mystifying, for goliaths are large, slow-moving, and have no fear of humans, making them easy prey for spearfishing. Hunting the giant groupers is about as exciting as bringing down a cow with a shotgun.

Groupers remain protected under federal law, but they may have found a way to strike back at their only predator, man. Increasing phosphate mining and fertilizer runoff in the Gulf of Mexico have nourished huge blooms of poisonous algae--poisonous to humans, that is, not to groupers. Studies have shown that 3 to 7  percent of Caribbean residents and tourists are poisoned by the condition called ciguatera annually. The results may be minor--consisting of nausea, vomiting, and itching--or they may be serious, resulting in neurologic symptoms similar to multiple sclerosis and lasting many years. One percent of ciguatera sufferers die.

Ciguatera poisoning is something to be concerned about when eating goliaths. They live so long that the chances of their becoming infected are greater than for their much smaller cousins. Cathleen Bester of the Florida Museum of Natural History assures us that cases of ciguatera poisoning are very rare. Those of us who studied probability in school may not consider a 7 percent possibility of infection as very rare. Horse racing aficionados observe that 10-1 shots frequently finish in the money.

On the other hand, Lori Bester of the National Institute of Environmental Health Sciences reports that ciguatera is the most commonly reported marine toxic disease in the world. Lori suggests that you should never eat barracuda or moray eel and should exercise caution with snapper and grouper. I suppose she means you can eat these fish, but just don't eat very much.

If there was ever a fish that encouraged overeating by its very size, the goliath would be it. So perhaps, if the ban on fishing is lifted, the great goliath unintentionally will take its revenge on man after all.

[Note: Research for this post was provided by Matthew Gamel, a graduate student at Florida Gulf Coast University. His help is appreciated.]

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