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BULLETIN OF THE BUREAU OF FISHERIES 
to avoid extremes of temperature seems to depend somewhat on the age of the fish. 
For example, Schmidt (1907, p. 23) found that cod during their first few years of life 
remained localized in the cold water of the north and east coasts of Iceland, but that 
as they approached maturity and the urge to spawn they migrated to a warmer 
region on the south coast, probably because they became more sensitive to external 
conditions. 
The extremes of temperature in which cod have been found range from around 
0° to about 15° C. and occasionally as high as 16° to 17° C., although in any given 
Figure 25. — Routes taken by ced which migrate or emigrate from Nantucket Shoals. The figures indicate the number of recap- 
tures reported from each general locality from 1923 to October, 1929. Total number of cod tagged on Nantucket Shoals, 22,228 
region the range ordinarily would be smaller than this. Bodies of cod living in very 
cold water, therefore, might respond differently to a given temperature than cod 
living in moderately cold water. Huntsman (1925), writing of the cod around the 
mouth of the Gulf of St. Lawrence, states that “For them 50° F. is rather too warm 
and 32° F, too cold, and possibly 40° to 45° F. would be considered just right. They 
