GROWTH AND AGE AT MATURITY OF THE PACIFIC RAZOR CLAM 
235 
SUMMARY 
The present paper deals with the Pacific razor clam {Siliqua patula) , a form 
of commercial importance along the entire northwest coast from Oregon to the 
Alaskan Peninsula. This is considered to be a single species throughout this range, 
the observed variations being due to environmental conditions. 
Spawning on the Washington coast takes place between the middle of May and 
the middle of June, while in Alaska the spawning season is less sharply marked 
and occurs from the first of July to the middle of August. Spawning apparently 
takes place on a sharp rise of water temperature at about 13° C. (55.5° F.). 
The larval stage endures about eight weeks, during the greater part of which 
time the young are in the surface sand. At the end of this period they appear 
in the intertidal zone as small clams, differing little from the adult in structure 
or habits. The " set " of these young is sometimes enormous on the Washington 
coast, but is never so heavy in Alaska. The mortality of the young during the 
first two years may be very heavy. A yearly census for the purpose of determining 
the success of each spawning year and its future effect on the commercial catch is 
recommended. 
The growth of the adult on various beaches has been determined from data 
obtained by a study of the annual rings. Norms are presented to shoAv the rela- 
tive rates of growth at the three places where the industry is most important. 
The size and age at maturity has been detennined by a study of the yonng 
clams. The size at maturity on all beds is in close agreement, but the age varies 
greatly. The relative influence of age and size on maturity has been determined 
mathematically and compared Avith other known forms. 
The only feasible criteria of overfishing are, first, the reduction in the average 
size of clams in the commercial catch and, second, the reduction in the average 
daily " digs " per man. A size limit has been proposed which, by protecting the 
small, immature clams, would prevent serious depletion of the beds now greatly 
overdug. 
BIBLIOGRAPHY 
Baldwin, Bied T. 
1921. The physical growth of children from hirth to maturity. University of Iowa Studies 
in Child Welfare, Vol. I, No. 1, pp. 1-411. University of Iowa Press. 
Belding, David L. 
1910. A report upon the scallop fishery of Massachusetts, including the habits, life history 
of Pecten irradians, its rate of growth, and other facts of economic value. The 
Commonwealth of Massachusetts. Special report of the Commissioners on Fish- 
eries and Game, 150 pp., 40 pis. Boston. 
1912. Quahog and oyster fisheries of Massachusetts. The Commonwealth of Massachusetts. 
Special Report of the Commissioners on Fisheries and Game, pp. 1-134, figs. 1-G9. 
Boston. 
