Chapter II 



MARINE ANIMALS THAT BITE 



SHARKS 



Probably the marine animals most generally feared by swimmers 

 and skin divers are sharks. Despite the vast amount of fiction, 

 legend, horror tales, and wishful thinking written about the sub- 

 ject, there are few facts available regarding the relationship of 

 sharks to man. Public opinion concerning shark attacks seems to 

 range all the way from "most species are dangerous", to "none of 

 them are noxious" to man. Scientific evidence and military and 

 civilian medical records lead one to believe that the facts of the 

 matter probably are to be found somewhere between these equally 

 untenable attitudes. 



The swimmer in shark-infested waters is confronted with four 

 important questions, namely: (1) which species of sharks are most 

 likely to attack, (2) how do you recognize them, (3) what are their 

 habits, and (4) what can be done to ward off an attack, if such 

 were to take place ? 



General. There are about 350 known kinds of sharks, but prob- 

 ably a score or less are believed to attack man. Sharks range in size 

 from the small scyliorhinids and triakids, which mature at a length 

 of only 18 inches, to the giant whale shark, which may attain a 

 length greater than 50 feet. It is consoling to know that this huge 

 monster feeds exclusively on small marine organisms. All sharks 

 are carnivorous, but most species are too small, inadequately armed, 

 or inhabit depths too great to be dangerous to man. The natural 

 food of the larger and more effectively armed sharks consists of 

 large fishes, other sharks, seals, and a variety of marine organisms. 

 If one is forced to generalize regarding the dietary habits of sharks, 

 it is safest to assume that if the shark is more than four feet in 

 length, adequately armed, and there is blood and food in the water, 

 it is potentially dangerous to man. 



A favorite topic of discussion among fishermen is the number of 

 series of teeth in a shark that are in actual use at any given time 

 (Fig. 1, Top). The number varies from four to five, depending upon 

 the species of shark and the part of the jaw concerned. In addition, 

 there are several reserve series in each jaw, with their points in the 

 reverse position, undergoing development. In this latter instance 

 they are covered over by a fold of mucous membrane and must be 



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