390 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
only this portion that is destined for the oysters. It is entirely of concrete, its waters 
drawn from the reservoir pond being now regarded as free of sediment and rich in 
food organisms. The density of the water (Jnly 19) remained constant in the canal 
and ponds at 1.023 (61° F.), a uniformity of saltness which is no doubt in part dependent 
upon the locks which occur seaward, and the tide water is perhaps proportional in 
incoming volume to the brackish water entering landward. 
It is certain that the conditions of water in the reservoir are extremely favorable, 
and that the food therein provided is sufficient to feed a half million of oysters thickly 
stacked, a remarkable number for an area so restricted. Processes like those of 
Marennes, intended to richen the supply of oyster food in the reservoir, do not appear 
to be employed. The water, naturally rich in suspended organisms and their food 
stuff, is perhaps bettered in its conditions for oyster feeding by remaining a day or 
two standing, and is made use of before becoming deaerated. The claircs of Marennes, 
on the other hand, renew the water but seldom (fortnightly), secure aeration by main- 
taining only a slight depth of water (10 inches), dry out the bottom regularly, and 
are even spaded up to richen the food stuff of the organisms which are to fatten and 
color the oysters. 
The Ostend principle of frequently changing the water in the reservoir renders 
it unnecessary to spade up or specially arrange the claire bottom, and at the same 
time does not tend to green the fattening oysters. The low claires at Marennes, 
where the water is often reuewed, produce white oysters, while the high claires , it will 
be remembered, develop the green moss, Amphipleura ( Navicula ) fusiformis ostrearia 
Grun., in quantity. Frequent changing of the water tends, moreover, to lower the 
mortality in claire culture. 
At Ostend oysters are received continually from England, France, or Holland, 
and are at once placed in the concreted compartments. They are banked several tiers 
thick, and are often arranged in a series of parallel alleyways formed by low board par- 
titions. Their time of arrival is registered, and a month is usually allowed them to 
acquire the taste and appearance of Ostend oysters. The only process to which they 
are subjected is that of cleaning and rearrangement. This is performed by the attend- 
ant before renewing the water supply, by shoveling them roughly to and fro in the 
different alleyways as the water is passing out. The roughness in this process may, 
from attrition, not improbably account for the smoothness of shell which forms one of 
the characters of the Ostend oyster. This local character, observes Leroux,* is 
also attained by a regular course of shaking the oysters in bags ; it is suspiciously 
claimed by the rival culturists of Zeeland that a stamping machine is in use to break 
the fringing edges and favor the production of a smoothly rounded shell margin. 
Higher water temperature marks a slight modification in the management of the basins. 
Oysters that are to remain during the summer are disposed not so thickly in the 
cemented compartments, are more frequently shifted about, and are given fresh water 
from the reservoir as often as twice a day. 
The importance of Ostend is understood when we consider the constant stream of 
oysters that passes through the dozen or more establishments during three-quarters 
of the year; and a calculation might, in a general way, be based upon the storage 
*Trait6 pratique d’ Ostreiculture, Nautes, 1881, p. 30. 
