314 Unwersity of California Publications in Zoology [Vou. 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. Hyen 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 nuttallt 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 434 billion bushels of Mya 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 
Atlantie Coast by the Massachusetts Commissioners on Fisheries and 
Game and on an economic seale by many eastern growers. The labor 
involved is shght. 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 obsoleta. It is to be hoped that the 
eastern winkles (Zunatia 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. 
