Ciguatera seafood poisoning
Ciguatera is a form of seafood poisoning caused by consuming fish or shellfish that contain high levels of ciguatoxins through bioaccumulation. These toxins affect the brain but can also cause gastrointestinal and cardiovascular symptoms.
Ciguatoxins are produced by several species of harmful algae called dinoflagellates, which are microscopic algae that live in the water and on several surfaces in coral reefs including macroalgae (les alges, Turbinaria) and dead coral. Bioaccumulation in relation to ciguatera happens when toxins produced by certain microalgae get stored in the bodies of reef fish. These algae are then consumed by fish such as maito (chirurgien, ctenochaetus striatus) and other small herbivores. The toxins accumulate in fish that consume a lot of the microalgae, and in the predatory fish that eat them like oeo (emperors, Lethrinus sp.), ha’amea (snapper, Lutjanus bohar), roi (groupers, mérou cephalopholis argus) and pa’aihere (trevally, carangeue, caranx sp.). Recently it has been reported that some shellfish like giant clams (Tridacna maxima) and urchins (Tripneustes gratilla) can be toxic, but this is not very common.
These fish are not always toxic, and traditional knowledge has helped us learn that some areas of the reef are more likely to have toxic fish than others. Outbreaks have been associated with changing environmental conditions like warm water temperatures, dredging and increases in macroalgae. However, researchers are still trying to understand why ciguatera is found in some places and at certain times but not others.
Unfortunately, ciguatoxins cannot be eliminated by cleaning, cooking or freezing the fish. Traditional methods have long been used to test if a fish is toxic, like checking for blood, a unique smell or giving a piece of the fish to pets or ants. However, there are still 10-70 cases of ciguatera reported in Moorea each year, and between 225-700 reported cases annually in all of French Polynesia. Researchers estimate the true number of cases is much higher as many cases go unreported. The best way to avoid ciguatera, according to fishers and health officials, is to avoid fishing in areas known to be toxic and avoid fish species that are high risk.
