MIGRATIONS OF COD 
61 
Round Shoal cod, owing to the presence of larger fish, for whereas only a small per- 
centage of the fish exceeded 24 inches long at Round Shoal buoy an appreciable 
percentage did so on the Chatham grounds. In the latter locality the small peak at 
Figure 21. — Length-frequency distribution of 299 cod caught on the Chatham grounds, about 12 miles ENE. of Round 
Shoal buoy, May 3-4 (solid curve), and 161 caught June 16, 1927 (broken curve) 
26 inches suggests that the Round Shoal G cod of September, 1926, may have mi- 
grated over the Chatham grounds and that a remnant of them were left behind. 
Or it may be that the G cod were present in large numbers on the Chatham grounds 
in 1926 and that the few present in May, 1927, were a remnant left behind after the 
others had departed. 
As a result of the fishing just described, it was found that the same school of 
cod which was dominant on Nantucket Shoals in 1926 was even more so in May, 
1927, extending from Round Shoal buoy to at least 10 or 12 miles east-northeast on 
the Chatham grounds and about 20 miles southward to Great Rip buoy. 
The second cruise to Nantucket Shoals in 1927 was made in June. The length 
frequencies of the cod caught then were almost identical to those taken in May at 
all three localities — Round Shoal buoy, Great Rip buoy, and the Chatham grounds. 
At Round Shoal buoy the great peak of 20 inches in May had been flattened 
very slightly and stood at 21 inches in June (fig. 20, No. 1), due to growth of the 
fish. All the large fish above 32 inches had moved away, probably to deeper water. 
At Great Rip the D cod were dominant at 22 to 24 inches, compared to 20 to 
22 at Round Shoal. (Fig. 20, No. 1 , and 22, No. 2.) The curve for June is smoother 
than that of May because a much larger sample of fish was taken, but virtually the 
same stock was present both months. 
On the Chatham grounds the May and June distribution is likewise very much 
the same, with the 20-inch peak moved over to 21 inches due to growth (fig. 21), just 
as occurred at Round Shoal buoy. 
Tagging also was done east of Davis Bank in June, 1927, and, although we 
had no previous data with which to compare, it is evident that the D cod extended 
to that region. (Fig. 22, No. 1.) Davis Bank lies about equidistant from Round 
Shoal and Great Rip buoys, and it was interesting to find that while the D cod were 
20 to 22 inches on the Round Shoal grounds and 22 to 24 inches on the Great Rip 
grounds they were 20 to 23 inches on Davis Bank. Whether it was water tempera- 
ture or food which caused the small differences in the size of the cod living on these 
three grounds, the intermediate position of Davis Bank appears to connect up the 
conditions existing on the other two. 
