192 BULLETIN OF THE BUREAU OF FISHERIES 



part of the basin, but the data are not sufficient to show whether or not it was more 

 plentiful in the offshore parts of the gulf than near land, as is so constantly and 

 characteristically the case in summer (p. 189). 



Our several sections across Georges Bank have shown that in summer the off- 

 shore boundary to abundant Calanus finmarchicus — indeed, to an abundance of 

 copepods of all kinds — abreast the Gulf of Maine is but a few miles outside the 

 continental edge (p. 21). Even on July 23 and 24 in the cold summer of 1916, when 

 Calanus was reasonably plentiful over the southwestern part of Georges Bank gen- 

 erally, it was represented by only an occasional specimen a few miles outside the 

 100-meter contour, where the general aspect of the plankton was more oceanic 

 (station 10352). 



During the cold half of the year Calanus spreads somewhat farther offshore. 

 It may even be extremely plentiful along the southeastern slope of Georges Bank in 

 early spring (p. 189), and on May 17, 1920, it was about as numerous at the outer- 

 most station off the western end of the bank (17,000 per square meter at station 

 20129) as in over the latter or in the neighboring part of the basin of the gulf to the 

 north, but it is probable that very few Calanus exist at any season more than a few 

 miles outside the 1,000-meter contour west of the longitude of Cape Sable. 



The regional distribution of Calanus is so irregular, with particular swarms 

 often so soon dissipated, and the relative abundance of the species in different regions 

 is in a state of such constant change, that it is not safe to postulate a typical rule for 

 it from its quantitative distribution at any given time; but sufficient data have now 

 been accumulated over a period of years to show (a) that Calanus finmarchicus is 

 far" more plentiful in the open waters of the gulf than in estuarine situations or 

 among the islands, and usually most plentiful some miles offshore; (b) that the 

 coastal belt inside the 100-meter contour, from Cape Ann northward and eastward 

 to the mouth of the Bay of Fundy, is a zone of comparative scarcity for it, as con- 

 trasted with the Massachusetts Bay region, the basin as a whole, or the northern parts 

 of Georges Bank; and (c) that the chief center of abundance is in the southwestern 

 part of the gulf, along Cape Cod, off Massachusetts Bay, in the neighboring parts 

 of the basin, and as far northward as the region of the Isles of Shoals. The eastern 

 basin, the northern channel, and the neighborhood of Cape Sable are secondary 

 centers, where Calanus is occasionally extremely plentiful, but we have never taken 

 it in frequencies as great as 100,000 per square meter anywhere else within the 

 gulf (fig. 66). 



In 1920 the stock of C. finmarchicus increased slightly throughout the coastal 

 zone generally between Cape Cod and Mount Desert from March to April, raising 

 the average numbers per square meter for this region from about 1,800 to about 

 5,000. 97 At the head of Massachusetts Bay, off Boston Harbor, there were some- 

 thing like four hundred times as many Calanus on April 6 (station 20089, 1,250 per 

 square meter) as on March 5 (station 20062, only 3 C. finmarchicus per square meter). 

 On the other hand, the Albatross found fewer Calanus in the eastern basin of the 

 gulf generally in April (average about 2,540 per square meter) than in March (aver- 



" Eight stations lor March and 11 for April. 



