442 
BULLETIN OF THE BUREAU OF FISHERIES 
ago a strenuous campaign was waged against them, the growers now appear to accept 
the damage passively. 
For some years the great problem of oyster growers has been the “cup”, Crepidula 
fornicata, which was presumably introduced into these waters with Eastern seed 
oysters. Although not a parasite, the species multiplied until many of the diked beds 
contained far more “cups” than oysters. Since the growers first became uneasy 
about them, they have paid the cullers extra for separating them out, and in this way 
have considerably reduced their numbers. However, even now it is not unusual for 
equal numbers of sacks of oysters and “cups” to be culled from a bed. The species 
appears to thrive much better in the diked beds than on the natural seepage grounds. 
Several kinds of predatory snails are found on the grounds. The native whelk, 
Thais lamellosa, occurs in great abundance; and the writer has found that these drill 
some adult oysters and, in places, a great many spat. They appear to attack mussels 
primarily. They were previously unrecognized as an active enemy but are now culled 
out along with the “cups.” Also, their habit, during the breeding season in late 
winter and early spring, is to come together in large clusters around a shell or rock 
where the egg cases are deposited. During this time they may be taken up in sacks 
and placed on the beach to die. The moon snail, Polynices cewisii, is frequently seen 
on oyster grounds but is primarily a clam borer and probably seldom attacks oysters. 
The Eastern oyster drill, Urosalpinx cinerea, introduced with seed oysters from 
the Atlantic coast, may be found in some places, though only in Samish Bay where 
Japanese oysters are now grown is it relatively abundant. Of greater potential 
importance is the Japanese oyster drill, Tritonalia japonica, which has been introduced 
with seeds from the Orient. Few Japanese seeds have been planted near the im- 
portant Olympia oyster grounds and no damage to native oysters has yet been noted. 
However, in Samish Bay, this drill has propagated rapidly and for the last few years 
has been causing tremendous mortality among the Japanese oysters. After a visit 
to Samish Bay in 1928, Galtsoff (1929) wrote: 
Although at present there is no evidence that Tritonalia japonica is destructive to oysters, yet 
as a matter of precaution it is desirable to restrict the planting of Japanese species to the waters in 
the northern part of Puget Sound and not to extend them to the areas where high-priced Olympia 
oyster bottoms are located. 
When the writer first visited this ground 4 years later a great many drilled shells 
were found. In 1935 there was evidence of still greater mortality. 
The rapid propagation of the species to dangerous proportions indicates the prob- 
lem which Olympia oyster growers may soon face, especially since the thin-shelled, 
slow-growing native oysters would probably be more easily attacked than the rela- 
tively heavy-shelled Japanese oyster. Unfortunately, Galtsoff’s suggestion was not 
followed, and it is known that the drills have been introduced near some of the native 
beds. On one ground in Oyster Bay a number of drills have been found, introduced 
presumably with Japanese oyster shells from Samish Bay. At the time of writing 
nothing is being done to prevent rapid spread of the pest to other grounds. 
At times starfishes become abundant enough to destroy many oysters, but these 
are readily removed from the cultivated beds. One of the greatest problems of growers 
is to maintain their dikes against the “crawfish” or mud-shrimp, Upogehia pugettensis, 
(MacGinitie, 1930) which has a habit of burrowing under the dikes and opening 
passages which are rapidly enlarged by flow of water, 
