GROWTH AND MORTALITY OF PACIFIC RAZOR CLAM 
551 
have been found at Pismo, Calif. The Washington beds produce clams up to 9 years 
of age, while the commercial catch in Alaska contains a large number of 13-year-old 
clams and ages up to 19 years have been recorded. In order that any valid com- 
parison of age may be made it is necessary that mortality data in the form of survival 
curves be available. 
Table 5. — Survival table showing numbers of clams still living at each age for each 100 clams forming 
first ring, and age of 5 per cent survival for each locality 
Year 
Pismo 
Crescent 
City 
Channel 
Sink 
Copalis 
Massett 
Controller 
Bay 
Karls 
Bar 
Swiekshak 
Hallo 
Bay 
1 
100.0 
100.0 
100.0 
100.0 
100.0 
100.0 
100.0 
100.0 
100.0 
100.0 
2 
92.0 
98.0 
97.3 
97.3 
98.5 
98.7 
99.0 
98.3 
97.6 
98.3 
53.7 
93.6 
91. 1 
96.4 
91.3 
95.8 
99.0 
97.0 
97.6 
96.2 
4 
10.5 
88. 1 
62. 8 
88.6 
83.6 
93.4 
99.0 
96.5 
89.6 
96.2 
5 
1.7 
79.3 
30.4 
76.5 
71.1 
71.8 
97. 8 
94.4 
84.3 
95.8 
6. 
60.3 
11. 9 
29.6 
53. 8 
54.7 
89. 1 
87.3 
80.4 
95.3 
7 
20. 9 
9.2 
2.6 
37.1 
47.7 
71.8 
86.0 
76. 9 
88. 7 
8_ 
4.4 
1.1 
1.8 
17.2 
33.0 
48.2 
54.3 
72.0 
80. 7 
9. 
.6 
3. 8 
12.2 
15. 9 
24.0 
62.5 
76. 9 
10 
2.0 
7.4 
14.6 
58.6 
72. 2 
11 
6. 1 
9. 7 
44. 8 
58.0 
12. 
3. 7 
5.8 
27.2 
46. 7 
13 
1.2 
3.2 
9. 5 
32. 3 
14 
1.3 
1. 8 
21. 8 
15 
1.3 
.4 
11.4 
16 
1.3 
3.0 
17 
1.3 
1.3 
18 
1.3 
19 
. 9 
Age (years) of 5 per cent 
survival - 
4.4 
7.9 
7.0 
7.0 
8.8 
9.6 
11.0 
12.0 
13.4 
15.6 
This need we were forced to supply from age-frequency data from the different 
beds. We have assumed, as did Lea for the herring (1924), that the frequency of the 
older ages represents a practical survival curve for that locality and have supplied the 
earlier portion by comparison with those based on the most adequate data. In the 
resulting curves for each locality, we located the smallest survival that could be 
accurately determined, which proved to be 5 per cent. This we have arbitrarily 
taken as the maximum age. (See Table 5.) The comparison of different localities is 
discussed in a later portion of this paper. 
GROWTH 
The data on the growth of the razor clam here presented were collected over a 
period of years from 1923 to 1928. We consider them unique in that the growth of a 
single species is recorded from 10 different localities, making possible a comparison of 
the general course of growth under the widely differing environments involved in 2,400 
miles of coast and 25° of latitude. We propose to consider (1) certain significant 
general tendencies common to all localities and to other animals, and (2) certain less 
significant differences due to the environment. 
As explained in former papers (Weymouth, 1923, 1923a; Weymouth, McMillin, 
and Holmes, 1925), the seasonal growth of the clam leaves its record in the shell as a 
series of age marks so that it is possible to measure not only the length of the shell 
at the time it was taken, but also its actual length at each previous winter of its life. 
We have thus available a complete record of the growth of the individual usually 
only obtained if the animal is reared and observed throughout life. Therefore, the 
norms of growth which we present are not based solely upon the size of the individuals 
