808 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [56] 
prevent any abrupt change of temperature. During the entire first year 
it will be well if the water never has a less depth than about one meter, 
and a strict guard will be necessary to maintain the dikes in good con- 
dition, repair all breaks, look out for the deposit of mud, and if any takes 
place change the oysters to another claire without delay. Later, in pro- 
portion as the oysters increase in size, and are less affected by external 
changes, this constant oversight can be relaxed to a certain extent, but 
not entirely, and the level of the water may be lowered to from .50 to .30 of 
a meter, always taking care, however, to increase the depth to 1.50 to 2 
meters during very cold or very warm weather. It will be readily under- 
stood with how much caution the level of these basins should be lowered, 
when it is remembered that it is only possible to fill them again at quite 
long intervals, eight to ten days generally, during which time, especially 
in spring and autumn, great changes of temperature may take place, 
exposing the oyster to evils against which there is no remedy. For 
young oysters, and especially during their first years’ growth, the most 
formidable enemy is mud. We have already spoken of transferring the 
oysters from a basin where the mud has accumulated or is being rapidly 
deposited to another which is free from mud, but this measure, which is 
excellent for oysters somewhat advanced in size, is not always satisfac- 
tory for the very young individuals ; and besides, at certain seasons of 
the year the temperature would render such a change impracticable. I 
would counsel the breeders then to use for the first year frames of gal- 
vanized iron, about two square meters in superficial area, covered with 
a netting of galvanized iron or zine wire, having meshes of such a size 
that the young oysters could not fall through. These frames could be 
supported upon four or eight legs from .20 to .30 of a meter in length, and 
arranged side by side in rows over the bottom of the claires, thus form- 
ing a double bottom with a space between the frames and the soil suffi- 
cient to accommodate the mud, which would then never trouble the oys- 
ters upon the frames. They could be left in this position the entire year, 
without disturbing them. After this time they should have sufficient 
natural vitality to be handled without danger, and could be placed upon 
the bottom of a fresh claire. Thus in the rearing of oysters, since five 
years are required for an oyster to become of marketable size, it will be 
necessary to allot five claires to the rearing of one generation, and to 
establish a series which shall render the production continuous. One 
claire in five should, therefore, be provided with the wire tables men- 
tioned above. The necessary expense of their construction and intro- 
duction would be compensated by the decreased cost of manipulation 
and attention, and the greater production from the claires. The employ- 
ment of these frames would be nearly indispensable for basins along the 
Shores of the Mediterranean, which, nearly always covered by the sea, 
are more liable than others to be covered by a deposit of mud, which 
can be cleared away only at considerable expense. During the first 
three or four years of such an enterprise one should, in order to procure 
