MIGRATIONS OF COD 
47 
Table 27. — Tagged cod that were recaptured more than once 
Tag number 
Date o f 
tagging on 
Nantucket 
Shoals 
First recap- 
ture, 
Nantucket 
Shoals 
Second recapture and locality 
231 
June 28, 1923 
do... 
Oct. 3, 1923 
Oct. 4, 1923 
Oct. 6, 1923 
Oct. 27,1924 
May 6, 1925 
Oct. 18, 1924 
Aug. 20,1925 
Oct. 15, 1923, Nantucket Shoals. 
Jan. 5, 1924, Rockaway, N. Y. 
Jan. 2, 1924, Rockaway, N. Y. 
Dec. 7, 1924, Cholera Bank, N. Y. 
Aug. 7, 1925, Nantucket Shoals. 
Sept. 12, 1925, Nantucket Shoals. 
Oct. 27, 1925, off Great Point, Nantucket Island. 
277 . 
12017 
Aug. 16,1923 
July 15,1924 
Sept. 8,1924 
Sept. 11, 1924 
May 5, 1925 
18674. 
21216 
21380. 
28015 
The additional check given by these “second” recaptures throws further light 
on the behavior of Nantucket Shoals cod. Thus we have cod Nos. 21216 and 21380, 
whose recapture records indicate that they may have spent the winter on the shoals 
without having migrated westward, for they were caught three times in the same 
immediate locality; and cod Nos. 277, 12017, and 18674, which, although they did 
winter in the New York region, nevertheless spent the summer, up to at least October, 
on the shoals. It is of interest to note that although cod No. 28015 was recaptured 
locally, both on August 20 and on October 27, the last recapture being off Great 
Point, was at the extreme western part of the shoals — an indication that this fish 
had begun its migration into the Rhode Island-North Carolina region. 
THE CHATHAM GROUNDS 
Although only a small number of cod were tagged on the Chatham grounds, 
several of them were recaptured a sufficient time later to indicate that part of the 
stock of fish spent the summer there without migrating away. (See Table 16 on 
p. 27.) So, although no tagged Chatham ground cod were recaptured locally during 
the winter or during the summer which followed, this is perhaps due to the small 
number of fish that were marked, coupled with the inevitable loss of tags rather than 
to all the fish having moved away. 
LOCALIZATION AS SHOWN BY LENGTH FREQUENCY DISTRIBUTIONS 
Up to this point we have discussed the localization of cod on Nantucket Shoals 
as shown by tagged fish. Although this method has thrown considerable light on 
the movements of the cod, it has been found possible to corroborate and even to 
amplify the results obtained from tagged fish by an analysis of length-frequency 
distributions. 
It is obvious that if the relative proportion of fish of different lengths on a certain 
ground varies from month to month, or from year to year, not in accord with the 
normal growth schedule, either some age classes have been locally depleted or others 
reinforced. Consequently, we may hope to trace the movements of bodies of fish 
onto or away from any given bank, or the interchange of schools between different 
banks, by analyzing the length frequencies of unselected catches taken at intervals. 
We concentrated our tagging, therefore, on certain parts of Nantucket Shoals 
(fig. 14), for by so doing it was possible to detect slight changes in the lengths of any 
given body of fish and also to learn whether many of them emigrated away or whether 
new immigrants had appeared in the locality in question. 
105919—30 4 
