108 DANGEROUS MARINE ANIMALS 



ent circumstances, or in some other locality, will not produce violent 

 intoxication and rapid death. 



The big question is how do fish become poisonous, and what are 

 the factors contributing to the condition? All of the details as to 

 exactly how fishes become poisonous are not known at present. 

 However, it is believed that in most instances fishes become poi- 

 sonous because of their feeding habits. The poison is believed to 

 originate in a marine plant. Plant-eating fishes feed on these plants 

 containing the necessary chemical substances, and the poison is 

 either accumulated or manufactured in the body of the fish. Car- 

 nivorous fishes feed on the plant-eating fishes, and the poison is 

 thereby distributed to other groups of fishes. As in the case of 

 paralytic shellfish poison the toxic materials do not affect the fish, 

 but are lethal to man when sufficient quantity of the material is 

 eaten (Fig. 66). Scombroid poison develops in an entirely differ- 

 ent manner, and this will be discussed later in the chapter. 



Poisonous fishes are widely distributed throughout the world, 

 but occur in greatest numbers in tropical waters, particularly in the 

 West Indies and the tropical Pacific. Poisonous puffers, which are 

 extremely toxic, may be found in temperate areas, and the Green- 

 land shark, which under certain circumstances is poisonous, is 

 found in Arctic seas. 



TYPES OF FISHES POISONOUS TO EAT 



There are currently recognized eight general categories of marine 

 fishes 'whose flesh is dangerous to eat. However, only five of them 

 are of practical significance to the average person. 



POISONOUS SHARKS AND RAYS 



A number of deaths and many illnesses have been reported from 

 the eating of sharks and rays. Most illnesses have been caused by 

 tropical species, and the most severe poisonings have resulted from 

 eating the livers of tropical sharks. However, the flesh of the 

 Greenland shark, Somniosns microcephalus, Bloch and Schneider, 

 which inhabits Arctic waters, has been observed on numerous occa- 

 sions to cause intoxications in both humans and sled dogs. The 

 chemical nature of these poisons is not known. 

 Species Reported Poisonous: 



Black-Tipped Sand Shark Carcharhinus melanopterus (Quoy 

 and Gaimard) (Fig. 67, Top). Indo-Pacific, South Africa to the 

 East Indies, Hawaiian, Tuamotu, and Marianas Islands. 



