Variation in the toxins present in ciguateric narrow-barred Spanish mackerel, Scomberomorus commersoni.

Water-soluble and lipid-soluble toxins present in six specimens of Scomberomorus commersoni captured in subtropical Queensland were compared with those detected in a specimen studied earlier. All specimens were from batches that had been involved in human poisonings. All specimens contained significant amounts of potent water-soluble toxins, the most important of which in terms of contribution to the lethal potency of fish flesh was unidentified toxic material which tested positively for alkaloids. All specimens contained lipid-soluble toxins including ciguatoxin-like and scaritoxin-like material, the latter usually predominating. Amounts of water-soluble toxins with lethal potencies ranging from 14.9 MU to 115 MU/100 g of flesh and of lipid-soluble toxins with lethal potencies ranging from 8.8 MU to 39.9 MU/100 g of flesh were found. (A mouse unit, MU, is the minimum amount of toxic material expressed in g required to kill a 20 g mouse within 24 hr following i.p. injection.) The lethal potency of water-soluble toxins per g of fish exceeded that of lipid-soluble toxins per g of fish for five of the seven specimens of S. commersoni now investigated. Based on a lethal dose to humans of 2500 MU all fishes contained lethal amounts of toxic material. The relative amounts of water-soluble and lipid-soluble toxins present in the flesh of a specimen of S. commersoni were altered by different cooking procedures.