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 jinmarchicus — 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 jinmarchicus 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. jinmarchicus 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. jinmarchicus 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- 
97 Eight stations lor March and 11 for April. 
