378 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
feet that the water of the basin has been left a month without endangering its inmates. 
For rapid growth, it is found best not to place the oysters too thickly, a maximum of 
fifty per square yard. The water (sp. gr. 1.026+) is practically that of the sea, the 
bottom containing no springs and there being no ingress of little streams. Hence, to 
avoid too great a density from evaporation it is deemed advisable to renew the water 
more frequently than otherwise required. It is probably on account of the extreme 
saltness that production can not be attempted. I have personally no doubt that, if 
it were practicable to temper the density of the lake by a careful introduction of fresh- 
ened water, and to maintain it at the specific gravity of Breneguy, production might 
be both possible and profitable. 
CLAIRES: SPECIAL PROCESSES, SUCH AS u G-REENINGr” OR PREPARING- FOR 
TRANSPORTATION. 
On either side of the great lake at the Sables extend meadow and marsh lands, 
suited for salt-making. Here have been formed, by means of turf-covered banks, rect- 
angular pond-basins (50 by 150), arranged to be occasionally filled from the lake with- 
out (Plate lxxvi, Fig. 2). Our oystermen would be surprised that oysters could be 
kept alive, much less grown or fattened, in such small and muddy salt ponds. They 
are nevertheless the claires, famous for fattening the oyster or for giving it a color 
or special flavor. The bottom of the pond is like a plowed field, perhaps slightly 
more clayey; the sloping sides are turfed to the water’s edge. The water, maintained 
at the depth of but a few feet, is naturally muddy and continually causes sediment, 
which would be of extreme detriment if the pond basin had not been arranged with a 
marginal ditch into which all sediment shifts, convenient for removal. It will be seen 
that the claire will be advantageous, yet at the same time dangerous to the oysters. 
They become continually coated with mud ; the water, renewed but once a week or 
fortnight, is malaerated, and the mortality is of course great. On the other hand, 
everything conspires to give the conditions for the richest feeding ; the minute plant- 
life that enters the claire is forced into luxuriant growth by warm and food-bearing 
waters, that are slightly freshened by surface drainage. At the Sables differences in 
temperature between claires and outside lake are from 5 to 8° F. ; in specific gravity 
the differences are from .001 to .002. There may naturally be all degrees of claires , 
small and large, some renewing their water every few days, others but a few days each 
month. It is the exuberant growth of the oyster that makes claire culture profitable. 
In special localities entire elevage would not be practicable on account of the rate of 
mortality. The oysters when grown are simply introduced in the claires for several 
weeks to give them an esteemed taste or color. 
Claires must be studied at Marennes, a locality long known to produce oysters 
green or bluish-green in color and deemed exquisite in taste. Green oysters have 
become synonymous with Marennes, their reputation, if not their flavor, commanding 
a high price in the market. Nowhere else along the French coast are found conditions 
as favorable for elevage as well as for u greening.” The low-lying tide lands, clayey, 
but rich in peaty mud, produce the richest of oyster food, clouding the slow waters 
with minute plant life. Of these low organisms, by far the greater number are dia- 
toms, a race of minute, single-celled plants that often possess a curious power of nav- 
igating about apparently at will. They are transparent, incased in a delicately fretted 
