JAPANESE OYSTER-CULTURE. 
19 
THE JAPANESE OYSTER -ITS KINDS AND NATIVE CONDITIONS. 
Three kinds of Japanese oysters are to be considered in this connection. First, 
a small one, probably a dwarfed salt-water variety of Ostrea cucullata Born., is 
abundant along the southern and eastern coasts of Japan — by far the most abun- 
dant of its kind. This is a bay oyster, occurring in shallow water of specific 
gravity of about 1.020 to 1.026, where it forms an almost barnacle-like incrustation 
upon the tidal rocks. It is collected in great numbers for local consumption; fisher 
people open them on the spot, not detaching the shell from the rock, and market 
them by bulk. In actual size this oyster is rarely larger than one’s finger nail; but 
its flavor makes amends for its size. It is plumbeous in color. The shell measures 
rarely more than 2 inches in length; it is deeply crenulate, Gryphsea-like, at the 
margin. In size and flavor it suggests very closely the California oyster. 
The second form, Ostrea cucullata (cf. pi. 6, fig. D), is the important one from the 
culturists’ standpoint. Although not large, it averages the size of a “Blue Point,” or 
of an English “native.” The oyster itself is cream-colored, its shell delicately nacre- 
ous, well shaped, thin, deep, and with a series of imbricating, horn- like outgrowths, 
which suggest the shell of the European oyster, O. edulis. This species occurs 
abundantly throughout the Inland Sea, in the small bays along the northeast coast 
of the main island and at certain points in the Hokkaido (Yezo). It thrives best 
in the bays well tempered by fresh water, of specific gravity of 1.017 to 1.023. Its 
young are more abundant in the shallow and fresher water. The best that are mar- 
keted grow at a depth of a fathom or two below low-water mark; it is practically 
absent in water deeper than 8 fathoms. It is this species which will be considered 
through the remainder of the present report in connection with cultural methods. 
The third form, Ostrea gigas Thunb., is of large size, specimens weighing with 
shell 4 or 5 pounds being not infrequent. It rarely occurs in water less than 2 
fathoms deep and is most abundant in about 10 fathoms. The specimens which I 
examined were taken by divers in water of about 35 feet. It is a typical sea oyster, 
occurring in water of specific gravity of about 1.026. As far as I have been able to 
ascertain, its value is purely local, no region producing sufficient numbers to warrant 
a definite fishery. A large bank of oysters occurs in the Hokkaido, off the north- 
east coast, not far from the town of Akkeshi. The oysters here are said to be of 
extraordinary size, but during my visit to the Hokkaido I was not able to ascertain 
whether they represent this third species or whether they are large examples of O. 
cucullata. The latter species certainly occurs in the neighborhood. 
The oyster-producing region of Japan is par excellence the Inland Sea, and it is 
here that the culturists have carried on their industry with greatest success. This 
body of water can indeed be looked upon as one of the most important natural pre- 
serves of fish and shellfish in the world. It can be compared to a deep marine lake, 
but it is sufficiently open to the sea to insure favorable conditions of density and of 
renewal of its waters, while its occupants are free from the dangers of an open gulf. 
From the oyster-culturists’ standpoint the Inland Sea is remarkable in that its con- 
nection with the ocean is established both at its ends and near its middle point. 
Thus at the extreme east it opens to the ocean through the Straits of Naruto, as 
well as at the mouth of the Izuminada. At the west, 240 miles away, it opens again, 
this time to the Japan Sea, through the Straits of Shimouoseki, and to the south 
