110 
BULLETIN OF THE BUREAU OF FISHERIES 
Table 41. — The number of circuli formed within the first zone of growth on the scales of cod living north 
of Cape Cod compared with those living to the southward 
Locality 
Date 
Number of 
fish 
Average 
length, 
inches 
Average 
number of 
circuli with- 
in the first 
growth zone 
of scale 
North of Cape Cod: 
21 
23. 1 
15. 8 
Northeast Georges bank 
January, 1924 _ _ 
53 
38.2 
13.9 
Do 1 . . 
September, 1928 _ 
41 
28. 0 
16. 0 
Mount Desert, Me _ . __ _ _ 
August, 1924 
40 
16. 1 
15. 4 
Do 
August, 1928 - 
35 
18.7 
16. 9 
Platts bank __ _ 
April, 1927 
35 
26. 0 
14.9 
Stellwagen bank . _ 
July, 1924. - 
29 
25.3 
15. 6 
Do_. 
October, 1925 
44 
22.6 
14.9 
Total-- -. 
298 
15.3 
South of Cape Cod: 
South Channel... . 
June, 1929 
36 
26. 4 
20.6 
Nantucket Shoals 
Summer, 1923 
573 
26.3 
20. 1 
Do . . 
Summer, 1927. _ _ 
32 
22. 5 
19.0 
Do 
Summer, 1928 
62 
22. 2 
20. 1 
Cholera bank, N. Y __ 
November, 1927 _ 
50 
25. 2 
21.2 
Do 
November, 1928. 
36 
23.9 
21.3 
Atlantic City, N. J 
/March, . 
\April, 1928 
51 
25. 1 
21.3 
Total 
840 
20.5 
1 
Figure 32. — Frequency-distribution of the number of circuli within the first zone of growth on the 
scales of the cod listed in Table 41. Broken line for the north of Cape Cod; solid line for the south 
of Cape Cod. Smoothed ounce by a 3-class moving average 
There is unquestionably a significant difference in the count of the first-year 
scale circuli between the cod living north of Cape Cod and those living to the southward 
in the samples presented in Table 41. All these scale samples were selected at random, 
without respect to the size of the fish, so that small, medium, and large cod are included 
in almost every group of scales that was studied. Both the north of Cape Cod and 
the south of Cape Cod scales gave a simple mode in the frequency distribution of 
the first-year circulus count, as shown in Figure 32. 
Regardless of what may have caused this marked difference (whether differences 
in the rate of growth or in the time of spawning), the fact that it exists indicates that 
the stocks of cod living north and east of Cape Cod are for the most part distinct from 
those living to the southward in that the fish from the two regions do not intermingle 
in a large way. 
