THE AGE AND GROWTH OF THE PACIFIC COCKLE ( CARDIUM 
CORBIS, MARTYN ) 1 
By FRANK W. WEYMOUTH, Ph. D., Department of Physiology, Stanford University 
and 
SETON H. THOMPSON, Temporary Assistant, United States Bureau of Fisheries 
CONTENTS 
Page 
Introduction 633 
Age determination 633 
Growth 634 
Growth in different localities 637 
Conclusions 639 
Bibliography 640 
INTRODUCTION 
Cardium corbis, commonly known as the “cockle,” is the most abundant and 
important species of Cardium found on the Pacific coast. It is widely distributed 
along the Pacific coast from southern California to the Pribilof Islands, Alaska, and 
as far south as Japan on the Asiatic shore. (Dali, 1916.) In the north it is found on 
tide flats in the bays, where it may be seen lying on top of the sand or barely beneath 
the surface. In the south it is found both in the bays and on the exposed beaches of 
coarse sand. The optimum locality for the species would appear to be in the Strait 
of Georgia, southern British Columbia, where they occur in great numbers. (Thomp- 
son, 1912; Weymouth, 1920.) 
Although the cockle is very abundant in many localities and is an excellent food 
mollusk, it has never attained commercial importance because of its poor keeping 
qualities and small edible content. The local markets absorb small quantities, and 
many are used by the crab fishermen for bait. Attempts have been made to can the 
cockle, but have not met with notable success. 
The data upon which this paper is based were incidentally collected by Dr. 
F. W. Weymouth, H. C. McMillin, and H. B. Holmes during the studies of the Pacific 
razor clam. Although the amount of material was relatively small, the homogeneity 
of the samples and the uniformity of clam growth have made it excellent material for 
growth studies. 
AGE DETERMINATION 
A quantitative analysis of growth data requires the knowledge of two variables— 
time and size. The absence of direct observation has required the use of the “annual 
rings” as measures of the time variable or age. The method is that which has long 
1 Submitted for publication Sept. 18, 1930. 
633 
