100 
BULLETIN OF THE BUREAU OF FISHERIES 
These records give a general idea of the growth of cod fry off southern New 
England up to the age of about 6 months. At that time (in midsummer) they are 
about 3 to 4 inches long. 
It is but natural that there should be considerable variation in the size of the 
fry taken in the same catch. Not only is there some difference in the rate of growth 
among the fry, but the long spawning season makes it possible to catch on the same 
date fish all of which are less than 1 year old but some of which are as much as 6 
months older than others. Thus in July or August 3 and 9 month old cod may be 
taken together. As a rule, however, although there may be a wide difference between 
the extreme sizes in a large catch of cod fry, most of the fish are of a rather uniform 
size, indicating either that they were derived from eggs spawned in some definite 
area and at a particular time during the spawning season, or that fish of a size tend 
to school together. 
It is unfortunate that no catches of cod fry adequate for length-frequency deter- 
minations have been recorded from southern Massachusetts for the fall or the winter. 
But the many specimens of cod about 5 to 7 inches long observed in the stomachs of 
fish caught on Nantucket Shoals in September and October indicate that the fry 
living in this region attain a length of about 7 to 8 inches long when approximately 
1 year old. 
The scarcity of cod between 10 and 15 inches long taken in our catches on Nan- 
tucket Shoals already has been commented upon. Length-frequency data for these 
sizes are therefore lacking for this region, but some idea of the rate of growth of 1 to 2 
year old southern Massachusetts cod might be had from a catch that was observed 
on Georges Bank. (Fig. 28.) These fish were taken in September and had a well- 
defined mode at 30 centimeters (about 12 inches). Their scales showed but one 
annulus, with a wide periphery of summer growth, so they were probably about 1% to 
1 % years old. 
If these fish are of the usual size attained by 1 % to 1 % year old cod on the offshore 
grounds in the Gulf of Maine and if the rate of growth of the fish on Nantucket 
Shoals does not differ materially from this, then we might expect cod in the latter 
region to be about 14 to 15 inches long by the time they are 2 years of age. 
Data on the growth of cod 2 years or more of age have been obtained from the 
length-frequency distributions of cod caught throughout our fish-tagging operations. 
Graphs dealing with these fish have already been given (figs. 15 to 24) in discussing the 
stock of fish on Nantucket Shoals. From these certain groups of fish have been 
selected to show rate of growth and are presented in the table which follows. The 
mean length of the cod in each group was calculated by selecting arbitrarily as many 
inch classes (usually three or four) as can be identified with a mode. For example, 
the average size of the B group of July 13-17,1924 (fig. 16, No. 1), was calculated to 
be 23.9 inches by obtaining the weighted mean of the 23, 24, and 25 inch fish. This 
method must admit of some degree of error in locating the modal length of each 
group, but this is unavoidable because it is impossible to obtain the true mean length 
of the fish included in a “dominant group,” as the limits of such a group are in this 
case unknown. But even if these limits were known, they probably would alter the 
calculated length but little. 
The value of these calculations depends largely on whether or not we are dealing 
for the most part with fish from the same population. That we are doing so is sug- 
gested o j he ease with which the dominant groups A to I) (fig. 24) can be identified 
from the time they were first found on Nantucket Shoals until they passed out of 
