MIGRATIONS OF COD 
69 
leave northern waters on the approach of winter and pass that season in the ocean 
south of Newfoundland.” In the Barentz Sea, where the annual temperature range 
on bottom is from about 0° to about 5°, Averinzev (1928, p. 117-126) found that cod 
and haddock appeared to change ground in order to keep in water of 3° to 4°, shunning 
0°, although even in the latter temperature some cod were caught. However, these 
latter observations do not prove that the cod shifted ground as a result of a direct 
thermal stimulus, for it may have been that in the warmer water a more abundant 
food supply was present and attracted the cod thither. 
The nature and extent of the cod’s migrations depend largely on the geography 
of its environment, in conjunction with the other factors just mentioned. For 
instance, the maturing Icelandic cod which migrate from the north to the south 
coasts might very well continue farther if it were not for the deep water (400 to 
600 meters) between there and the Faroes. In the same way the migrations of 
the Faroes fish are restricted because this bank is surrounded by water deeper than 
that ordinarily frequented by the cod. The long migrations of European cod, 
from Lofoton to the Finmark coast (Hjort, 1914, fig. 69), and from Finmark back 
to Lofoton and even southward (ibid., fig. 134), and of American cod from New 
England to as far as North Carolina, are allowed by the fact that there are no depth 
barriers to stop them, and the temperature, at certain seasons at least, is favorable 
all along the route. But passive factors such as these can not be supposed to pro- 
vide a stimulus for a regular seasonal migration. 
Nantucket Shoals cod make two distinct migrations— one into the Rhode Island- 
North Carolina region each winter and the other, during certain summers, into the 
Chatham-South Channel region near by. (Fig. 25.) As these two migrations 
differ in route, season, and regularity of performance, the possible causes for them 
are discussed separately. 
There are, in addition to the fish just mentioned, which travel over a definite 
migratory route, other cod which straggle into the region north of Cape Cod. Why 
so few cod go eastward and north from southern Massachusetts is not known. Appar- 
ently these southern grounds afford a very favorable environment for the cod, so 
that most of the fish which enter it remain there for an extended period. This 
could still be true, and yet there would be no danger of the cod overpopulating 
the grounds, for not only is a regular fishery carried on there most of the year, but 
in addition large numbers of them are caught during their sojourn on the wintering 
grounds to the westward. 
THE WINTER MIGRATION 
Spawning as a possible cause . — It might be considered significant that the 
spawning period of the cod off the New England coast coincides with the time when 
the migration to the westward of Nantucket Shoals takes place. But Nantucket 
Shoals itself is an important spawning ground, and it is not likely that cod from 
there would journey as far as 200 or 300 miles west and south to spawn in a region 
apparently unsuitable for them during the summer when so many other cod remain 
to spawn on the shoals, while others gather there for that purpose. 
It might again be suggested that the cod which summer on Nantucket Shoals 
are the ones which go west for the winter, and that the fish which spawn in winter 
on the shoals come from farther east. But tag records have shown that most of 
the few fish tagged on Stellwagen, Georges Bank, and off Nova Scotia, and which 
are known to have migrated toward Nantucket Shoals, passed on, for they were 
recaptured between Block Island, E. I., and Rockaway, N. Y. Furthermore, 
