Ciguatera is a foodborne illness poisoning in humans caused by eating marine species whose flesh is contaminated with a toxin known as ciguatoxin, which is present in many microorganisms (particularly the micro-alga Gambierdiscus toxicus) living in tropical waters.
Like many naturally and artificially occurring toxins, ciguatoxin bioaccumulates in lower-level organisms, resulting in higher concentration of the toxin at higher levels of the food chain, an example of biomagnification.
Predator species near the top of the food chain in tropical waters, such as barracudas, snapper, moray eels, parrotfishes, groupers, triggerfishes and amberjacks, are most likely to cause ciguatera poisoning, although many other species have been found to cause occasional outbreaks of toxicity.
Ciguatoxin is very heat-resistant, so ciguatoxin-laden fish cannot be detoxified by conventional cooking.