Fishes of the Western North Atlantic 249 



about 10° to 15° C. (50°-59° F.) ; it does not appear on the coast of the Middle Atlantic 

 United States or southern New England until the bottom water has warmed to at least 

 6° to 7° C. or higher} it departs in autumn when the temperature falls below about 10° to 

 12° C. At the opposite extreme, specimens kept in the tanks at Woods Hole show no ill 

 effects at the highest summer readings which are usually up to about 22° to 23° C. or 72° 

 to 73° F., but there is some evidence of withdrawal locally when the water warms above 

 about 70° F. The Caribbean populations of the species are inhabitants of tropical tempera- 

 tures. 



Between North Carolina and Cape Cod the Smooth Dogfish moves north and south 

 regularly with the seasons, wintering chiefly within the sector between the southern half 

 of North Carolina and the offing of Chesapeake Bay. In the southern part of this range 

 many are caught in beach seines at times during the cold months. We have found odd 

 specimens on the flats in Pamlico Sound in early winter, chilled to death by the sudden 

 onset of freezing weather. Further north, however, along the southern Virginia coast, 

 where water temperatures are lower, winter records of them are chiefly from the offshore 

 fishing banks, in depths of 30 to 60 fathoms, where they are abundant enough to be a 

 nuisance. 



The northward migration is progressive from early spring on, considerable numbers 

 lingering in North Carolina waters until June, with occasional specimens present there into 

 July, although none are seen thereafter. They appear by May along the peninsula that 

 separates Chesapeake Bay from the Atlantic," and they arrive nearly simultaneously at 

 about this same season all along the coasts of New Jersey, New York and southern New 

 England, the average date of their vernal arrival at the entrance to Long Island Sound 

 for a fifteen-year period being May 10, the earliest record being May 2. As a rule they 

 also appear in appreciable numbers at Woods Hole some time in May. However, the date 

 of their vernal arrival varies locally from year to year. Near New York, for example, 

 they usually are not plentiful until June. They summer all along the coast from Delaware 

 Bay to Cape Cod in such numbers that every fisherman is familiar with them, and they are 

 also present to some extent along the outer part of the continental shelf off southern New 

 England (p. 248). But the return movement of "Smooth Dogs" southward from south- 

 ern New England may commence as early as July, a decrease in their numbers often having 

 been reported there after June, with a corresponding increase in their numbers from sum- 

 mer to September near New York and offshore on the outer edge of the continental shelf. 

 But no mass movement southward takes place until late October or November, when they 

 withdraw almost simultaneously from the coast line as a whole to as far south as Chesa- 

 peake Bay, though stragglers (most often small specimens) may linger in the vicinity of 

 New York, and no doubt elsewhere, as late as the second week in December during some 

 years." Presumably they also withdraw from the outer edge of the continental shelf off 



16. For some reason, odd specimens only have been taken within the Bay. 



17. Latest date for the mouth of Long Island Sound, Dec. 13. 



