MIGRATIONS OF COD 
53 
(fig. 15, No. 2), or they may have come from some part of the shoals where no tagging 
had been done and from where, therefore, no length frequencies had been obtained. 
It is more likely, however, that the cod centering around 30 to 32 inches, as well as 
the 15 to 17 inch fish, C, came from grounds north or east of the shoals, because we 
learned in the years which followed 1924 that at least a small part of the cod living on 
Stellwagen Bank, Georges Bank, and particularly in the Chatham-South Channel 
region join in the fall migration to the westward of Nantucket Shoals. 
Around Great Rip buoy and Davis Bank 89 cod were taken in October — too few 
to show graphically. There were, however, no small fish present, and a predominance 
of sizes, irregularly distributed between 25 and 34 inches, suggesting that some of 
the Round Shoal B cod (23 to 26 inches) as well as of the school of uncertain identity 
(30 to 32 inches) extended that far south on the shoals. 
The year 1924 in summary: 
The dominant size group of cod, A, present in 1923 on all the Nantucket Shoals 
tagging grounds left the Round Shoal-Rose and Crown buoy grounds some time before 
July, 1924, and they were found to be traveling eastward toward the Chatham- 
South Channel region during that month. The B cod which first appeared on the 
Round Shoal buoy grounds in October, 1923, formed the dominant group on the 
various Nantucket Shoals tagging grounds throughout the summer of 1924. They 
appeared in large numbers some time between October, 1923, and July, 1924, but 
just when we can not say surely, as no fish tagging was done within this period. 
Very likely most of them migrated to and occupied the Nantucket Shoals grounds 
before the close of 1923. The stock of cod inhabiting the shoals throughout the sum- 
mer of 1924 carried out no migrations that included large numbers of fish, nor were 
their numbers augmented materially during that period, but during October, 1924, 
a school of cod that was apparently on its way westward to spend the winter appeared 
on the tagging grounds. Some of these very likely remained on Nantucket Shoals 
throughout the winter and did not continue westward. 
LENGTHS OP NANTUCKET SHOALS COD IN 1925 
No track was kept of the cod on Nantucket Shoals during the winter of 1924-25 
nor during any of the otherwinters throughout our tagging operations. We are obliged, 
therefore, to jump from the fall to the next spring or summer in taking up the analysis 
of the length frequencies. 
In preparing the length data for our May cruise to Nantucket Shoals in 1925 
the Round Shoal to Rose and Crown region was subdivided into three areas — one 
being within about a mile of Round Shoal buoy, another in the vicinity of Rose and 
Crown buoy, and the other between the two buoys, which were about 6 miles apart. 
Very much the same length frequencies were obtained from each of these areas, 
excepting that a slightly greater proportion of larger fish was taken around Rose 
and Crown buoy, and, because there was no important difference, all the lengths 
were combined in the same graph. (Fig. 17, No. 1.) 
This first cruise to the shoals was particularly interesting, for there was some 
speculation as to whether the small cod below 20 inches in length, which first appeared 
the preceding October, would still be there in the spring. It will be remembered 
(fig. 16, No. 3) that in October, 1924, a small peak was formed by the 15 to 17 inch 
fish, C, which sizes comprised 7.4 per cent of the total catch of cod. This same stock 
of fish, C, was present on the shoals in the spring of 1925 and apparently was augmented 
