222 
BULLETIN OF THE BUREAU OF FISHEEIES 
The Washington curve shows the> fastest growth, followed by Swickshak and 
Cordova, in the order named. The first point on each curve represents the average 
size of the young clams from the respective beds during the first winter. The 
Washington clams reach an average size of 2 centimeters, in contrast to % centi- 
meter for Alaska. This is due to the later spawning in Alaska and the earlier 
suspension of growth, due to the shorter season, which is about one-half as long 
as for the southern beds. The young clams of Alaska are very difficult to find 
during their first year. Plankton tows taken at Cordova on August 17, 1924, 
showed a large number of half-grown larvse, which could hardly have settled soon 
Age in Years 
Fig. 15. — Swickshak clams. Graph showing the average length of each age (solid line) and the 
average age of each length (broken line). The latter is irregular in the first three years, due 
to the necessity of using one year as an interval of time. Center line shows the median or 
age, and the lines above and below show the 90th and 10th percentiles, respectively 
enough to make appreciable growth before the Avater temperature dropped below 
the point where growth is possible. 
"While there is not a great difference in the final size of clams from various 
beds, there is a marked variation in the rate of growth during the first few years. 
As has already been stated, clams from the Washington beds reach maturity at 
about 10 centimeters in two years, while those from Swickshak and Cordova do 
not reach a similar size before three and four years, respectively. . The legal size 
of 11.44 centimeters (4i^ inches) is reached at the following ages: Washington, 
3.5 years; Swickshak, 5 years; and Cordova, 6.3 years. The growing season in 
Alaska, as already mentioned, is roughlj' one-half as long as in Washington. 
