PLANKTON OF THE GULF OF MAINE 189 



localities in this zone during April and May of 1887, while Fowler (1912) reports it in 

 great abundance along the New Jersey coast in June, 1911, and early July, 1912. 

 In cool summers, such as that of 1916, it continues extremely plentiful along the 

 zone of lowest temperature on the shelf, narrowing to the southward to abreast the 

 mouth of Chesapeake Bay until the end of summer and becoming much less plentiful 

 in autumn, as I have described in a previous report (Bigelow, 1922), but in warm 

 years — e. g., 1913 — it practically vanishes south of New York by July (Bigelow, 

 1915, p, 269). So far as known, the latitude of Chesapeake Bay may be set as the 

 southern limit to its occurrence off the east coast of the United States in numbers 

 sufficient to color the plankton at any season. Westward and southward from 

 abreast of Cape Sable the zone of abundance for Calanus finmarchicus is bounded 

 offshore by the high temperatures and salinities of the "Gulf Stream," a boundary 

 which fluctuates in location from season to season but which is never far outside the 

 edge of the continent. 



Regional distribxdion in the Gulf of Maine. — In the gulf Calanus finmarchicus is 

 decidedly more oceanic than neritic (p. 35), but exists to some extent in estuarine 

 situations as well as offshore. I can offer little first-hand information as to its 

 occurrence in inclosed waters, most of our stations having been located out at sea, but 

 it has appeared in abundance in Gloucester Harbor (p. 194), and we have likewise 

 taken it in abundance in the harbors of Kittery, Portland (Bigelow, 1914, p. 117), 

 Eastport, Provincetown, and in Casco Bay. Doctor McMurrich, in his manu- 

 script list, records it regularly at St. Andrews, often in abundance, during the 

 winter of 1915-16, from November through April, but only occasionally during the 

 later spring, summer, or early autumn. Willey (1921) found it in abundance in the 

 mouth of the St. Croix River during the winter of 1916-17, but decidedly rare in the 

 winter and spring of 1919 and 1920. If these observations in the St. Andrews 

 region apply equally to other parts of the shore line of the gulf, Calanus finmarchicus 

 is to be classed as a winter copepod in estuarine waters, where it has never been 

 found in the swarms in which it often occurs in the open sea. Williams (1906) 

 similarly found it an abundant winter visitor to Narragansett Bay, and Fish (1925) 

 found it in winter and early summer at Woods Hole. 



Outside the estuaries and inside the continental edge, Calanus finmarchicus is 

 universal in the Gulf of Maine, both in deep water and over the shoal banks, but it 

 is consistently less abundant in the coastal zone northward and eastward from Cape 

 Ann along Maine and Nova Scotia than off Massachusetts Bay and in the basin in 

 general. Although the distinction between regions fertile and poor in Calanus is 

 apparently least marked in early- spring, when the species as a whole is least plentiful 

 in the gulf, the chart for February and March, 1920 (fig. 64) shows no frequencies as 

 great as 3,000 per square meter anywhere in the peripheral belt inside the 100-meter 

 contour between Cape Ann and Cape Sable, with the whole of Georges Bank equally 

 barren except for the transitory swarm of Calanus which we encountered over and 

 off its southeastern slope on March 12, 1920, as I have described (p. 168). On the 

 other hand, all but one of the vertical hauls in the basin and in the channels (eastern 

 and northern) yielded more than 1,500 Calanus finmarchicus per square meter, and 

 most of the hauls more than 5,000, with a maximum of 33,700 in the western basin. 



