324 EIGHTH PACIFIC SCIENCE CONGRESS 



conditions, any fish-like vertebrate is capable of developing (concentrat- 

 ing or metabolizing— which?) ichthyosarcotoxins which can be lethal to 

 man. (2) Poisonous fishes are widely distributed throughout the torrid 

 zone, and some species are known to occur in temperate and arctic 

 waters. (3) A fish that is a valuable commercial species in one area 

 may be poisonous to humans in another locality. Hence, conclusions 

 derived trom an epidemiological survey in one area may have little or 

 no bearing upon the incidence or identification of poisonous fishes else- 

 where. Distances of even a few miles may entirely alter the epidemiolog- 

 ical picture. (4) The problem is not a static one. Fish species which 

 were once edible and commercially valuable species have within the 

 last ten years become poisonous. The situation which has occurred at 

 Line, Johnston and Midway Islands may be cited as classical examples. 

 There are no valid statistical data whether the over-all incidence of fish 

 poisoning is probably on the increase. (5) There is no correlation be- 

 tween the incidence of toxicity and season of the year in most species. 

 Instances of intoxication commonly occur throughout every season of the 

 year. (6) There is no simple field test whereby a toxic fish can be dis- 

 tinguished from an edible one. A poisonous fish appears in form and 

 action no different than a non-toxic fish. 



The question of why a fish becomes poisonous is a difficult one to 

 answer. Numerous theories have been propounded, but few of them 

 harmonize with the field observations. The reader is referred to the 

 works of Gudger," Hiyama '' and Halstead "^ for a more complete review 

 of these theories. There is no single exjolanation that will satisfy the 

 entire picture. 



Recent studies indicate that ichthyosarcotoxins evolve from a num- 

 ber of different sources and through the interplay of a variety of phy- 

 siological processes. Hence the term 'ichthyosarcotoxism' is an all-em- 

 bracing one in which are included a number of different and distinct 

 clinical entities. This is indicated by the symptomatology of humans 

 resulting, for example,* from the European barbel {Barbiis harbiis 

 [Linnaeus]), the Pacific puffer (Arothron hispidus [Linnaeus]), the 

 Greenland shark {Somniosus microcephaliis [Bloch and Schneider]), 

 the bluefin tuna {Tliunnus thyinnis [Linnaeus]), the inoray eel (Gym- 

 nothorax flavimarginatiis [Riippell]), and red snapper {Lutjanus vai- 

 giensis [Quoy and Gaimard]), are quite distinct. Nothing is known re- 

 garding the origin of the poisons found in fresh-water fishes, such as the 

 barbel, nor in sharks. The histamine-like poisons found in scombroid 

 fishes (tuna, bonito, mackerel, etc.) are believed to be tissue break- 

 down products, possibly the result of bacterial action. Such fishes as the 



• The fishes listed are representative of various groups of poisonous fishes which are capable 

 of producing different types of intoxications. 



