248 Memoir Sears Foundation for Marine Research 



are taken in pound nets, as well as on hook and line close to bottom or actually on it. How- 

 ever, we are told by a well informed fisherman that a few are also caught along the outer 

 edge of the continental shelf on the so-called "Tilefish Grounds," in the offings of New 

 York and of southern New England, in depths of 80 to 90 fathoms during June and 

 September; and the species is described to us as a midwater form around Cuba.^^ 



Its food consists chiefly of the larger Crustacea, with crabs of one species or another 

 ranking first in most localities. It also preys largely on lobsters, of which it is perhaps the 

 most destructive enemy ofF the southern New England coast, where lobsters have been 

 found to form up to 1 6 per cent of its food. Smooth Dogfish also feed on squid, especially 

 in spring, and on whatever small fish may be available, such as menhaden (Brevoortia), 

 tautog (Tautoga), puffers (Spheroides), sticklebacks (Gasierosteus), scup (Stenotomus) 

 and sculpins (Myoxocephalus) . It has been estimated that in Buzzards Bay 10,000 

 Smooth Dogfish might annually devour over 60,000 lobsters, and perhaps V5 million 

 crabs, as well as possibly 70,000 fish of one kind or another. They also feed on mollusks to 

 a lesser extent, both univalve and bivalve, as well as on worms (Nereis). And they swallow 

 considerable quantities of eel grass (Zosiera), although probably only incidental to the 

 capture of their animal food.^^ They are also scavengers when occasion offers; off Havana, 

 for example, they have often been taken with garbage (chicken-heads, etc.) in their stom- 

 achs." Experiments have shown that food is found chiefly by the sense of smell,^* although 

 they also have fairly keen vision for nearby objects. A crab, for instance, is found as quickly 

 when hidden as if lying in the open. In captivity, and no doubt at liberty also, they con- 

 stantly search the bottom for food. When a crab is found it is shaken to and fro and de- 

 voured. It has also been observed in the aquarium that they never molest active fish, but 

 soon devour any sick or injured specimens, suggesting that it is only the smaller fishes that 

 they normally capture in any considerable numbers. 



The fact that every female of i,000 mm. or longer taken at Woods Hole in the first 

 half of July during a recent investigation had either ovulated or was in the process of so 

 doing shows this to be the mating season. Corresponding to this, many kept in captivity 

 became pregnant during the late summer. The period of gestation appears to be about ten 

 months, i.e., the Smooth Dogfish carries her young during the winter migration.^" Off 

 southern New England the young are born between early May and mid- July, when new- 

 born specimens are often caught in the pound nets. 



Such facts as are known regarding its winter and summer ranges show that the north 

 and south migrations of the northern stock of this species are chiefly thermal in nature. Thus 

 the temperature of its winter home ranges from about 6° to 7° C. (43°-45° F.) up to 



11. Personal communication from Luis Howell-Rivero. 



12. For lists of stomach contents and estimates of destructiveness, see Field (Rep. U.S. Comm. Fish. [1906], Spec. 

 Pap. 6, 1907: 12, 15). 



13. Personal communication from Luis Howell-Rivero. 



1 4. Sheldon, J. exp. Zool., 10, 1 9 1 1 : 51; Parker and Sheldon, Bull. U.S. Bur. Fish., 32, 1913: 33; Parker, Bull. U.S. 

 Bur, Fish., 33, 1914: 61. 



15. Unpublished studies by F. L. Hisaw and A. Abramowitz. 



