Growth Indices of the Clam Mya Arenaria

Abstract

Newcombe and Kessler (1936) have presented a study of the growth indices of Mya arenaria L. as found in four widely separated localities on the Atlantic Coast. In the present study data from spring and fall collections from two localities on the shore of San Juan Island in the State of Washington are presented and compared with each other and with the findings of Newcombe and Kessler, which are re-examined. Although it was possible to make only a single small collection from the estuarine mouth of the Siuslaw River in Oregon, the data obtained there are included because of the extremely favorable conditions for the growth of the clam in that locality (Edmondson 1922). The present stock of Mya arenaria in the inland marine waters of the State of Washington and of British Columbia is generally considered to be descended from Atlantic stock accidentally introduced into Pacific waters not more than 80 years ago (Keep and Baily 1935: 117118). There are, however, indications (Newcomb 1875; Newcombe 1893; Oldroyd 1924) that Mya arenaria may be native in the Puget Sound-Strait of Georgia region. Hence, any differences found between clams of this area and those of the Altantic cannot unquestionably be referred to environment alone. For aid to the furtherance of this investigation the following are acknowledged: Curtis L. Newcombe of the U. S. Public Health Service and Oscar W. Richards of the American Optical Company for suggestions concerning the work; a number of citizens of San Juan Island for permission to collect clams from their tide lands; and the State of Washington funds for medical and biological research for financial aid. METHODS