EUROPEAN METHODS OE OYSTER-CULTURE. 
375 
. 
Tims, in theory, an oyster protected from crab and starfish by a raised gauze- 
covered case gets thrifty feeding conditions without danger of becoming engulfed by 
mud or sand. The amount of spawn produced by the oyster thus favorably reared 
becomes increased, a far larger proportion of the young are secured by the artificial 
devices, and this progeny is so situated that their natural enemies may be watched and 
destroyed. Conversely, the enemies, thus artificially circumvented, find less nourish- 
ment, spawn less prolifically, and run continued danger of destruction from the traps 
of culturists. These results destructive of the biocoenose would none the less happen, 
be it understood, granting that the food quantum, as Mobius states, is an altogether 
limited one. But in the case of oysters living in what is practically an open sea, the 
food supply does not appear to be of the strictly limited character that Mobius has 
assumed. Aud his illustration of the car]) in a small pond producing no more than a 
definite weight in annual yield, does not seem to be absolutely pertinent. Nor would 
the comparison be closely applicable even if the number of carp were supposed to be 
taken from the pond and set free in an open river. Their yield in weight would 
doubtless be greater, but even then fish food is not to be compared either in quantity 
or in capacity for exhaustion with the minute oyster food plant-life which is con- 
tinually transferred through a limitless volume of sea water. The boundaries of a 
natural bank are certainly not fixed by food quantum. The food stuff may, it is true, 
vary in quantity in different regions during the same season, or in the one locality at 
different stations, seasons, or even tides.* But there seems in general to exist a food 
normal which is recognized as characteristic of a locality. 
Aside, however, from this question of local variation, the amount of food that is 
♦actually brought to an oyster colony seems to the writer to be in direct proportion to 
the volume of water passing over it. If this volume be infinite, as it is in the Watten- 
meer, exhaustion of food supply would seem an impossible condition. Barrenness and 
sterility of water could not occur; general transfusion of floating or of free-swimming 
micro-organisms is very clearly one of the characters of the open sea. The lower 
water layers that may have been screened out by a thrifty oyster bank would not 
remain without organisms, but would immediately be replenished from above by the 
currents that exhausted the lower layers. The writer had this impressed upon him 
in its practical aspect while examining the various cultural establishments of the 
French, Dutch, and Belgian coasts. The test in these instances seems a fairer one, 
since the side- dependent questions of sediment accumulation and danger from enemies 
is excluded by the cultural device of wire-gauze cases. 
In a situation where the water volume becomes an extraordinary one, myriads of 
oysters are cultivated. At points where this water volume is increased by currents 
the cultural possibilities are found to become almost limitless. At Ossegor, for exam- 
ple, near the lower end of the lake, where the water is constantly changing, the cases 
were arranged in continuous lines, utilizing every available point,! each case contain- 
ing about a thousand oysters, so tightly packed edgewise that it would seem almost 
* Cf. however, New York State Report of Oyster Investigation, 1886, p. 72 et seq.; U. S. F. C. Bul- 
letin, 1890, 344-349. 
t IT. S. F. C. Bull., 1890, 375, PI. lxxiv, Fig. 2. 
