196 Edible Moliusca of the Oregon Coast 
sach month throughout the year. In the Siuslaw River the 
species spawns during the late summer the period closing about 
the middle of September. Fully formed spermatozoa may be 
detected about the first of July while usually by the 15th of 
September the bodies of both males and females are in a spent 
condition. Later in the year and during the winter and spring 
months young, immature ova and spermatocytes in various stages 
of development are present. The height of the spawning season 
in this locality seems to be the latter part of August and the first 
week in September (Figure V, 10, II, 12). 
By the latter part of November young clams from Io to 
25 mm. in length may be found in the beds just under the sur- 
face of the mud beneath patches of eel grass. The eel grass 
serves as a hold-fast for the embryonic clams which cling to it 
by their byssus threads until they are of sufficient size to dig into 
the soft mud. 
Kelloge® reports that the breeding season of Mya arenaria in 
Buzzards Bay extends from the latter part of May to the early 
part of August, reaching its height in late June or early July. 
Local conditions probably determine the spawning period of this 
species in each locality. 
The rapid growth of Mya arenaria, especially when young, 
and the demonstration of the success of replanting depleted areas 
make this species a suitable one for experiments in clam culture. 
Rapidity of growth depends, naturally, upon a number of condi- 
tions such as the character of the bottom, currents, exposure 
between tides, amount of food, etc. It has been shown by Kel- 
logg, as cited above, that clams from 1 to 1% in. long when 
planted may reach a fair marketable size in one year’s time. 
Nightingale* has pointed out that clam culture will insure a 
uniform supply and restore depleted beds to their former pro- 
ductivity, and that clams artificially planted under favorable con- 
ditions will mature in from 9 to 14 months while in natural beds 
from 2 to 3 years may be required. 
Measures should be taken to replant portions of the beds of 
° Kellogg, J. L. Conditions governing existence and growth of the soft-shell clam 
(Mya arenaria). Part 29, Report of the U. S. Commissioner of Fisheries for year 1903, 
pp. 195-224. 
7 Nightingale. H. W. Concerning the Mortality of the Soft Clams at Essex, Mass. 
Economic Circular No. 16, U. S. Bureau of Fisheries, April 8, 1915. 
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