MIGRATIONS OF COD 
51 
31-inch cod which had been tagged when 29 inches long in August, 1923, in the 
immediate vicinity of the buoy. Furthermore, many of the cod tagged in 1923 on 
Nantucket Shoals were subsequently recaptured during 1924 and 1925 a little to the 
eastward on the Chatham grounds and South Channel. And to show that it was 
chiefly this predominating size group which carried out this eastern migration we 
have the following data: 5,015 fish, or 66.4 per cent of the total of 7,554 cod caught 
on Nantucket Shoals in 1923, were 25 to 30 inches in length ( A cod), while 23 fish, 
or 74.2 per cent of the total of 31 recaptures made on the Chatham grounds and in 
South Channel, from June, 1924, to August, 1925, were of cod which measured 25 to 
30 inches on Nantucket Shoals in 1923. 
Figure 16. — No. 1 =length-frequency distribution of 486 cod caught at Round Shoal buoy July 13-17, 1924. No. 2=length-frequency 
distribution of 964 cod caught from Round Shoal buoy to Rose and Crown buoy, September 6-11, 1924. No. S=length-frequency 
distribution of 795 cod caught from Round Shoal buoy to Rose and Crown buoy, October 16 to 28, 1924 
With this evidence we can conclude that most of the individuals belonging to 
this great school of fish (1923 A cod) immigrated to the Chatham-South Channel 
region some time between the fall of 1923 and the summer of 1924, for they were not 
observed bn Nantucket Shoals thereafter. Many of them probably migrated west- 
ward in the fall of 1923, the survivors of this migration returning to Nantucket 
Shoals in the spring and continuing eastward toward the Chatham grounds. Almost 
all the fish above 33 inches likewise left the Round Shoal buoy grounds over the 
winter of 1923-24, for they were not present there the summer of 1924. 
The 20 to 22 inch fish, B, which first appeared in October, 1923 (fig. 15, No. 1), 
evidently immigrated to Nantucket Shoals in large numbers some time during the 
winter of 1923-24, for on our July cruise we found that they formed the predominat- 
ing group at Round Shoal buoy. (Fig. 16, No. 1.) They had grown to 23 to 25finches 
