Carolinas to Argentina cat sharks are exclusively 

 inhabitants of the continental slopes. Atlantic 

 American records of Apristurus are for the most 

 part from depths of 750 to 1500 meters, and lower 

 latitude records of other cat sharks in the region 

 are from depths of 200 to 750 m. 



Along Atlantic American coasts, fewer hauls 

 have been made in depths in excess of 1,000 m. than 

 in shallower water and trawling has been limited in 

 areas where rough bottom topography produced 

 severe gear losses. Deficiencies in the representa- 

 tive quality of the collections are due chiefly to 

 these factors. 



Ford (1921), writing about Scyliorhinus cani- 

 cuius at Plymouth, England, noted that there is a 

 curious alternating seasonal predominance of the 

 sexes in adults. In the winter the males were 

 found to be the predominant sex, whereas in the 

 summer the females were the more numerous. 

 Differential preferences by the sexes for depth 

 (and by inference for temperature) were noted by 

 Springer (1960) in shallow-water carcharhinid 

 sharks. This may be true also of some of the cat 

 sharks. The importance of segregation by size as 

 a means for protecting the young against preda- 

 tion by members of their own species is less ap- 

 parent for cat sharks than for the large voracious 

 earcharhinids, but perhaps is a useful trait. It is 

 of interest in this connection that Ford (1921) 

 reports Scyliorhinus stellaris feeding on the 

 smaller S. ccmi-culus in the Plymouth area. 



Nearly all specimens of cat sharks from the 

 western Atlantic have been taken in trawls. Most 

 of those collected by exploratory vessels were 

 caught in shrimp trawls having 1%- or 2-inch 

 mesh (stretched). Only the smallest sizes, less 

 than 6 inches, would be able to escape through the 

 meshes; larger cat sharks, over 24 inches long, 

 might sometimes evade the nets. 



WESTERN ATLANTIC GENERA 



The cat sharks known from the western Atlan- 

 tic fall into five well marked groups correspond- 

 ing to the five genera recognized here. Differences 

 of species within genera in the western Atlantic 

 are not great except between the two species of 

 Iliihieliiriis reported from Argentina. Of the 

 five western Atlantic genera, one genus, Apris- 

 turux, is probably cosmopolitan in waters of suit- 

 able depth outside of Arctic and Antarctic Re- 



gions. Galeus is present both in the North Atlan- 

 tic and North Pacific Oceans but has not yet been 

 found in the Southern Hemisphere if recognition 

 is accorded Whitley's genus Figaro (1934). 

 Schroederirhfhys is restricted to the Caribbean 

 and tropical Atlantic. Western Atlantic mem- 

 bers of the genus Scyliorhinus form a compact in- 

 frageneric group differing less from one another 

 than from species found in the eastern Atlantic or 

 in the western Pacific. Halaehirus, as understood 

 here, includes species from the Indo-Pacific region 

 and the Southern Hemisphere. 



The area of marine situations suitable to most 

 of the species of cat sharks is very small in com- 

 parison to the total ocean area. Apristurus, which 

 on Atlantic American coasts is found most com- 

 monly at depths from 750 to 1,500 m. and may 

 range into deeper water, occurs over a much 

 greater geographical area than species of other 

 genera, possibly being present in ocean basins of 

 moderate depths. Figure 1 showing the extent 

 and distribution of bottom along the Atlantic 

 coast of temperate North America at depths be- 

 tween 100 and 500 fathoms illustrates the rather 

 narrow bands in some areas to which cat sharks 

 may be restricted. Along tropical and subtropical 

 western Atlantic continental slopes, the ranges of 

 cat sharks other than Apristurus are extremely 

 narrow bands. 



The largest of the western Atlantic species prob- 

 ably do not ordinarily attain a length as great as 

 80 cm., and the smaller species (one species of 

 Scyliorhinus, one Apristwus, the three American 

 Gafaus, and Schroed-erichthy*) probably do not ex- 

 ceed 50 cm. Some eastern Atlantic and South 

 African species are larger. Scyliorhinus stellaris 

 (Linnaeus) of the eastern Atlantic reaches a 

 length of 150 cm. in the Atlantic but only about 

 75 cm. in the Mediterranean (Tortonese, 1956). 

 Smith (1949) gives maximum sizes of 4 feet (122 

 cm.) or more for Scyliorhinus capensis (Midler 

 and Henle) and Conoporoderrna africanwm 

 (Gmelin) of South African coasts. 



At the present time, a revision of the family in- 

 volving a review of generic or family classifica- 

 tions using some of the more advanced modern 

 methods that are available is impractical because 

 insufficient descriptive data exists for most named 

 species. Furthermore, it is very likely that a rela- 



584 



U.S. FISH AND WILDLIFE SERVICE 



