58 
BULLETIN OF THE BUREAU OF FISHERIES 
about 1 inch longer than the Round Shoal 0 cod had increased their dominant 
lengths from 21 to 22 to 25 to 26 inches. 
The D cod formed the dominant school at Great Rip in September. The fact 
that they averaged about 2 inches greater in length than the Round Shoal fish caused 
some speculation as to whether the fish from these two regions belonged to a homol- 
ogous group, particularly as no D fish were found at Great Rip the preceding August. 
The problem appeared to be whether or not the 18-inch Round Shoal to Rose and 
Crown cod were the same age as the 20-inch Great Rip cod. It seemed entirely pos- 
sible that if the Great Rip fish found more and better food over an extended period 
than the Round Shoal fish they could have amassed a net gain of about 2 inches in 
length in about a year’s time. 
Fortunately, scale samples of all these fish had been obtained, so that by a study 
of these it was possible to see if such a growth was registered. As the smaller size 
group, D , made up the larger part of the stock of cod at both Round Shoal and Great 
Rip Bouys, the scales of these fish were examined, but time was not taken to compare 
the C Round Shoal cod with the supposedly C Great Rip cod. 
Taking them in the order of their tag numbers, the scales were studied of the 
first 50 Round Shoal cod that measured 16% to 19% inches (which sizes are rated at 
17 to 19 inches on the graphs), and the first 50 Great Rip cod that measured 18% to 
21% inches (19 to 21 inches on the graphs), thus including the dominant group of 
D cod in each locality. All these fish proved to be between 2 and 3 years of age, except 
2 Round Shoal and 1 Great Rip fish. In addition to these lots of scales another, con- 
sisting of 49 fish from Round Shoal, 18% to 21% inches long, was compared with the 
Great Rip fish of the same size. The first two lots of scales are given in the table which 
follows : 
Table 29. — A comparison in the number of peripheral circuli formed on the scales of certain cod living 
at Great Rip and Round Shoal buoys, Nantucket Shoals, during the summer of 1926 
Round Shoal buoy 
Length in inches 
1655-1654--- 
17- 1754 
18- 1854 
19- 1914 
Total 
Great Rip buoy 
Number 
of fish 
Average 
number 
of periph- 
eral 
circuli 
Length in inches 
Number 
of fish 
Average 
number 
of periph- 
eral 
circuli 
5 
5.4 
1855-1854 
6 
6.6 
17 
5 . 2 
19-1954 
19 
8.6 
18 
5.7 
20-2054- 
20 
8.6 
8 
6.6 
21-2154 
4 
8.7 
48 
5.6 
Total ___ 
49 
8.4 
As all these fish were of the same age, as measured in years, if would matter 
little if the larger fish (19 to 21 inches) had hatched a few months before the smaller 
ones (17 to 19 inches) because the scales of all of them began the formation of the 
“summer” rings at about the same time during 1926. Therefore, if circuli indicate 
growth the greater number formed at the periphery of the Great Rip scales is a 
good indication that these fish were growing at a faster rate than the Round Shoal 
fish. Even the 18% to 21% inch Round Shoal cod (which may be considered the 
fastest growing of the D fish at Round Shoal) averaged only 7 peripheral circuli as 
compared to 8.4 for the Great Rip fish of the same size (which may be considered as 
average growing D fish at Great Rip.) 
