A small thresher shark, Alopias vulpinus. A 14-foot specimen of this species, recently taken was estimated to weigli 

 approximately 500 pounds and possessed a caudal lobe measuring 7j feet. The long caudal lobe is apparently used to stun 

 prey. 



the white sharks, are streamlined and 

 possess large stiff pectoral fins for 

 stabilizers. In contrast, most rather 

 sluggish sharks, such as the cow 

 sharks, nurse sharks, and even the 

 bull sharks, are less streamlined and 

 often more bulky, or display adapta- 

 tions to other ways of life. The large 

 ■whale sharks, which engulf and strain 

 their prey in great volumes of water, 

 have terminally placed mouths to better 

 facilitate their feeding. The basking 

 sharks have extremely ^vide mouths 

 nearly terminal in position to better 

 engulf and strain great quantities of 

 water. Most other sharks have their 

 mouths placed far ventrally. 



Several deep-sea species, includ- 

 ing probably the little green dog shark 

 that lives at depths exceeding 1,000 

 feet, possess the ability to produce 

 light in their otherwise totally dark 

 environment. 



Relation to Man 



The relation of sharks to man 

 stems from commercial utilization of 

 sharks and shark products by man and 

 from damage caused man by sharks. 



Until 1950, a commercial fishery 

 for sharks was carried on in the United 

 States, on both coasts, and the annual 

 catch reached a maximum of 4.5 mil- 

 lion pounds landed on the Atlantic coast 

 and 39 million pounds on the Pacific 

 coast. The fishery was carried out 

 chiefly to obtain the shark-liver oil 

 which is rich in vitamin A. Byproducts 

 of the oil industry included: hides, 

 used for high-quality leather products; 

 fins (of some species), sold as spe- 

 cialty food items; meat, salted or sold 

 fresh as food for human consumption in 

 some areas; carcasses, ground into 

 meal; and teeth and vertebrae, cleaned 

 and sold to curio shops. With the advent 

 of cheaper sources of vitamin A, shortly 



