52 
BULLETIN OF THE BUREAU OF FISHERIES 
during the interim. That these fish belonged to the same school present the preceding 
fall is indicated by the Halcyon’s recapture at Round Shoal buoy in July, 1924, of 
12 cod 23 to 25 inches long, 5 of which measured 19 to 23 inches long when tagged 
there in 1923. Apparently this 23 to 25 school, B, was a large one, for even on the 
grounds 5 to 12 miles east-southeast of the buoy they were abundant enough to 
stand out in the length-frequency distribution (fig. 15, No. 2), although they were 
greatly exceeded in numbers by the 28 to 32 inch cod that were presumably moving 
eastward. 
On the cruise made September 6 to 11, 1924, most of the fishing was done on the 
grounds extending from Round Shoal buoy to Rose and Crown buoy. Practically 
the same size distribution was obtained from the 298 cod caught at the Round Shoal 
buoy grounds as from the 637 caught between the buoys, so the total catch of 964 
fish from both localities are combined in the graph. (Fig. 16, No. 2.) On the grounds 
6 to 8 miles east-southeast of Round Shoal buoy the remnant of the 1923 A cod 
present in July, 1924, had seemingly disappeared by September, as only a few scatter- 
ing fish were taken there at that time. 
It is apparent that the 23 to 25 inch July cod (fig. 16, No. 1) were predominant 
on the tagging grounds in September; but at that time, due to increased growth, they 
were 23 to 26 inches long. (Fig. 16, No. 2.) Small fish were absent and large fish 
above 33 inches were still scarce. The picture was, therefore, almost exactly the same 
as obtained at Round Shoal buoj^ in July, 1924, and illustrates how stationary the 
cod must have been throughout the summer. 
Two successive cruises were made to Nantucket Shoals within the period October 
16-28, 1924, and, as shown by Figure 16, No. 3, the size distribution which obtained 
in July and September was very much altered. Whereas the July and September 
length frequencies showed that no important immigration or emigration of cod 
occurred to or from Nantucket Shoals throughout the summer (unless a school of 
cod migrated to or from Nantucket Shoals and had the same length frequencies as 
the fish already on the shoals; such an instance is possible but not probable, as our 
data have shown), the October distribution showed that migrations of some sort 
were taking place, otherwise such a disturbance in the sizes of the cod present would 
not have occurred. The 23 to 26 inch B cod of July and September still formed a 
large part of the stock of fish present from Round Shoal to Rose and Crown buoys in 
October, but at least two other schools of cod had appeared in this region. One of 
them was comprised of 15 to 17 inch cod and will be designated as C fish. These, 
although apparently few in number, were destined to form a very important part of 
the stock of fish on Nantucket Shoals in 1925. The other school was a somewhat 
heterogeneous lot of large cod centering around 30 to 32 inches, some of which were 
present previously. The presence in October of these latter two size groups naturally 
tended to reduce the proportion of B cod considerably below that which was present 
in September. The departure of some of the B cod to the westward would also have 
reduced their percentage in the total stock of fish. 
The appearance in October of these two schools of cod (15 to 17 inches and 30 to 
32 inches, fig. 16, No. 3) agreed with the results of our cod tagging the year before, 
which showed that cod school up and migrate to the westward of Nantucket Shoals 
in the fall. It is possible that the cod centering around 30 to 32 inches may have 
been a return of part of the A fish which predominated on Nantucket Shoals in 1923 
and which last were traced to the east-southeast of Round Shoal buoy in July, 1924 
