Ciguatera poisoning is caused by ciquatoxin, produced by reef plankton. Some fish that directly eat the plankton, kole and palani for example, build up dangerous levels of the toxin, and all reef predators that eat the fish that eat the plankton accumulate the toxin. Human consumers of tainted fish gradually accumulate enough of the toxin to the point it affects them. One fish with very high levels of ciquatera, or a slightly tainted fish that pushes the human consumer over the edge, can bring on a very bad experience.
It is believed that the ciguatoxin levels on the reef fluctuate seasonally, and thus, the species that have a reputation to be “hot” may or may not have dangerously high levels depending on whether a bloom is going on. Since most predator fish, like papio/ulua, kaku, etc, travel anyway, it’s not wise to think fish from one particular area is “safe”.
A few scientific studies have been conducted in the past decades. This one, by the Hawaii State Dept of Health, grouped species in fairly broad categories, indicating how many of the 736 implicated fish were of a broad species. “Jack Fish” caused the highest number of poisonings, and is comprised of papio, ulua and kahala. Surgeonfish (kole, palani, kala) is next, grouper (roi, hapuupuu), and snapper (wahanui, taape, uku, toau) follow. What’s not clear is the percentage of each species group consumed that didn’t cause a reaction.
In another publication, the Hawaii Seafood Council refers to a study conducted between 1999 and 2003, listing the top 10 fish species involved in ciquatera poisoning. Interestingly, uku (#7) is higher up in the list than wahanui (#9), yet you no longer hear of uku being “hot”. However, the web is full of references of how “hot” wahanui is.
In yet another survey, published by the Hawaii Dept of Aquatic Resources, divers speared roi in West Hawaii (Big Island) and Oahu, and autopsied them to determine ciguatera level. All the roi tested positive for ciguatera, with 25% of the West Hawaii ones and 8% of the Oahu ones at levels unsafe to consume.
Traditionally, big papio, ulua, kahala, kaku, wahanui and kole have been likely ciguatera suspects before roi were introduced to Hawaii. Even uku to some degree, but possibly less because uku feed at mid depths when they get bigger. So what does this all mean in regards to how safe your fish is to eat? To minimize risk, don’t consume large individuals of these species, and limit your reef predator consumption in general.