314 University of California Publications in Zoology [Vol. 13 



Mya arenaria was taken alive at 8 out of the 43 quantitative hauls, 

 and is represented by 32 living specimens, making an average per haul 

 for the entire bay of .76. This would equal approximately 1.5 bushels 

 per acre. This figure, however, representing the average for the bay, 

 is obviously of little significance. If those stations having a sandy 

 bottom are segregated, it is found that this type of bottom yields on 

 the average 1.1 living specimens per haul, or the equivalent of ap- 

 proximately 2.2 bushels per acre, assuming that all were of marketable 

 size. Even such a yield has no economic significance, since under 

 favorable conditions a yield of 500 bushels per acre is not uncommon. 



The quantitative dredge hauls indicate that Paphia staminea and 

 Saxidomus nuttalli are even less abundantly represented within the 

 adlittoral waters of San Francisco Bay. 



The intertidal zone, having an area of approximately 17,344,000 

 acres, yields what clams are now obtained from the bay, since dredging 

 is not at present locally employed. It is probable that at least 50 

 per cent of this acreage is suitable for the production of Mya arenaria. 

 If this is so, the tidal zone of San Francisco Bay would undoubtedly 

 support 4% billion bushels of 3Iya arenaria. If markets could be 

 found for such an enormous amount of sea food, an industry involving 

 millions of dollars might be established. 



This clam has been transplanted and raised experimentally on the 

 Atlantic Coast by the Massachusetts Commissioners on Fisheries and 

 Game and on an economic scale by many eastern growers. The labor 

 involved is slight. The planting consists of merely scattering the 

 young clams, obtained from localities where the set is heavy, at a rate 

 of fifteen to twenty per square foot. Six months or a year later, 

 depending upon the size planted or the size marketed, these may be 

 harvested. The investment need not be great. A boat and a set of 

 digging tools is all that is necessary. The returns are as great as 

 from an acre of cultivated land, since in Massachusetts the average 

 yield per acre is given by Belding and Lane as $450. 



Not all of the clams that are planted reach maturity. Losses may 

 be due to overcrowding, whereby the clam is pushed out of its hole 

 by its more vigorous neighbors, to shifting sand, mud or sea weeds, 

 or to enemies such as the starfish or certain predaceous gastropods. 

 The gastropods include Polinices lewisi and the exotic species Uro- 

 salpinx cinereus and Ilynassa ohsoleta. It is to be hoped that the 

 eastern winkles (Lunatia heros and L. duplicata), conspicuous ene- 

 mies of Mya, will not be inadvertently introduced in San Francisco 

 Bay along with the young oysters brought from the east. 



