SPAWNING AND SETTING OF OLYMPIA OYSTERS 
495 
this manner. In 1935 and 1936 the method has been put into practice on a large 
commercial scale, with floats filled with shells or manufactured collectors. Some of 
the growers have worked out a system of dividing the floats into a series of removable 
compartments, in which the cultch is placed, thus facilitating handling and minimizing 
possible storm damage. (See fig. 39.) Counts made on typical egg crate fillers or 
special-type collectors in 1935 showed that they caught an average of 5,000 to 10,000 
spat each. 
These floats may be anchored in the channels or pot holes of Oyster Bay, where 
they get a swift current of water. The manufactured collectors are always placed so 
that water will flow through the cells bringing abundant larvae and washing out silt. 
Most of the growers using the method at the present time are those who have satis- 
factory growing ground but lack adequate seed beds. Formerly these growers pur- 
chased what seeds they were able to get, but in recent years, since almost complete 
destruction of oysters on the State-owned seed beds of Oakland Bay following the 
beginning of operations of a nearby pulp mill, almost no seeds have been purchasable. 
The float method now makes it possible for anyone with growing ground to obtain 
abundant seeds at a cost considerably less than would be required to maintain seed 
ground for the purpose. 
CORRELATION BETWEEN SPAWNING AND SETTING 
In the foregoing account detailed descriptions have been given of observations 
of spawning activities and on setting of larvae throughout the several seasons under 
different conditions. It is of interest to consider reproductory activities in their 
entirety in order to correlate the initial spawning with the somewhat later setting and 
metamorphosis of the larvae. Coe (1932 a, b) stated that spawning in this species 
continues during at least 7 months of the year on the coast of southern California, 
while in British Columbia waters, according to Stafford (1914), “The spawning season 
appeared to extend from about May 20 to about the last of July, and to have reached 
its maximum about the middle of June." This is a total spawning period of about 
2 % months, and he observed a setting period of about the same length, from early 
July until nearly the middle of September. The investigations described above 
indicate a total spawning period of 3 to 4 months, although the most intense spawning 
activity is confined to a much shorter time. 
Stafford estimated that at least a month is required between spawning and set- 
ting, while Coe (1932a) stated: 
Shortly after they have been spawned into the water these young bivalves attach themselves to 
almost any kind of solid objects. The free-swimming stage is thus very short and the opportunities 
for dispersal are limited. 
In a similar manner Galtsoff (1929) wrote: 
It is noteworthy that, although the whole development of the Pacific oyster is about twice as 
long as that of the eastern oyster, the duration of the free-swimming stage, when the organism is 
subjected to the vicissitudes of life in the open water and is not protected by the mother’s body, in 
both cases lasts for about a fortnight. Thus, the fact that Ostrea lurida spends half of the period of 
its development within the brood chamber of its mother is of no particular advantage, and the free 
swimming larvae of both species have an equal chance to become prey to plankton-feeding organisms 
or to be carried away by the tides. 
Because of the fact that the free swimming larval period lasts for a month or more, 
as was noted above, it is obvious that there is great opportunity for dispersal ; and in 
view of the fact that the maternal individuals protect their larvae until they have 
developed to an advanced bivalve stage at which they are presumably able to protect 
