242 Shark and Company 



and South Africa, the number of species of sharks alone was set at 

 "about 350." 



During exploratory fishing cruises in the Gulf of Mexico from 1950 

 to 1955, the U.S. Fish and Wildlife Service vessel Oregon collected 630 

 species of fish. Of these, 62 species were sharks, skates, and rays— and 

 10 of these were described as "new species." Similarly, in 1944, Lionel A. 

 Walford, then aquatic biologist for the Service's Division of Fishery 

 Biology, reported "new species" in the Gulf of California, where sharks 

 are so abundant that the gulf's largest island is named TiZ??/r<9/2— Shark- 

 Island. "The Mexican sharks are not very well known to science," Wal- 

 ford reported. "Owing to their large size, they are poorly represented 

 in museums, and then only by immature specimens. Many of the differ- 

 ent species look very much alike, and are difficult to identify. Doubtless, 

 several have yet to be described and named . . ."^ 



Some of the anatomical variations that ichthyologists seize upon to 

 differentiate species may seem minor or minute to the non-expert. Bige- 

 low and Schroeder remark, for instance, that it is sometimes difficult to 

 identify some species of skates "without x-ray photographs to show the 

 level at which the tip of the rostral cartilage terminates relative to the 

 anterior rays of the pectorals." But it is of precision such as this that 

 scientific knowledge is distilled. 



As man's limited knowledge of the sea increases, it seems likely that 

 discoveries of new Selachian species will also increase. These ancient 

 fish, enduring the cataclysmic changes of the eons, have had more time 

 and opportunities to proliferate than any land vertebrate. 



Putting this vast group of greatly varied types into a reasonable 



~ The authors are not professional ichthyologists, and, in this work, they are not 

 advancing any theories. They are extracting from the extensive materials that have 

 been gathered from world-wide correspondence and from personal interviews with 

 authorities in America and Europe, such information about the sharks and their rela- 

 tives as they believe to be most reliable and of popular interest. 



They have been in the laboratories of some of the great scientists in this field and 

 have raised many questions to which at present there are no answers. Among them is 

 the possibility of cross-breeding among closely related species of sharks, which might 

 explain the small differences observed among specimens and some of the confusion in 

 the scientific classification of very similar species reported in various parts of the 

 world. Little is known about the breeding of sharks in general— or even where they 

 breed. The authors have seen parts of shark jaws that for years have defied classifica- 

 tion because of minute differences between them and species that have been identified. 



It seems logical, in view of the lack of definite genetic knowledge about the 

 Selachians, to presume that there is some interbreeding among them just as there is 

 among breeds of dogs. If this can be used as a premise, the conclusions of Cousteau, 

 Doukan, and others about the unpredictability of the behavior of any shark as an indi- 

 vidual, rather than as a member of a species with set patterns of behavior, comes more 

 clearly into focus. But individuals in any "pure strain" (if there is such) vary, too. 



The authors leave further speculation— and research— to those more qualified than 

 they. 



