746 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [64] 
numbers for the prosperity of the banks, or whether the beds have 
become impoverished. He will reach this conclusion from the number 
of oysters which he can catch with a certain speed of his vessel, and 
during a certain definite time which his dredge drags over the bottom. 
Those authorities who have control of the inspections of the oyster- 
fisheries might, therefore, be able to avail themselves of the services of 
skillful dredgers to find out the condition of the banks before they de- 
cide, each season, the particular places which can be fished and the 
number of oysters which can be taken from each. The inspectors at 
Arcachon, after observations extending over many years, have arrived 
at a definite conclusion in regard to the number of breeding oysters 
which it is absolutely necessary to retain upon the banks, in order to 
maintain them at that stage of fruitfulness necessary for a permanent 
and profitable oyster-culture. 
The report of January, 1877, upon oyster-culture in France says: 
“ Although the natural oyster-beds in the Bay of Arcachon are regarded | 
as breeding-beds, yet, nevertheless, the government allows them to be 
fished for some hours ever year, in order to remove the surplus of oys- 
ters.” This is a fundamental proposition which a judicious oyster- 
breeder must carefully consider if the greatest amount of profit would 
be gained. In accordance with this proposition, oysters should never be 
allowed to remain upon a bank after they have passed the period of their 
greatest growth and fecundity, or until they die of old age; but we 
should anticipate nature, which demands the death of the old and weak 
as an indispensable condition for the production and bringing to ma- 
turity of the greatest number of young upon any bed. I do not con- 
sider it, then, as for the best interests of the beds to prevent dredging 
upon one or all of them for any long periods of time. The French Gov- 
ernment has not, therefore, in my estimation, acted in the best interests of 
the beds, in entirely forbidding dredging upon a strip of territory which 
lies along the edge of the oyster-banks of Cancale and Granville. The 
object of this protection is to retain there an undisturbed stock of breed- 
ing oysters, from which to rejuvenate the impoverished beds of both 
these places. Upon such unfished beds the natural biocénotic balance, 
from which acertain definite average germ-fecundity results, will yery soon 
become established. But this will become less if, with the same propor 
tion of nourishment, more superannuated than mature oysters are to be 
found upon the beds. The productiveness of any territory will thus be 
much less, if it is left entirely undisturbed than if itis judiciously fished, 
and, moreover, the profits which result from the food-oyster taken from 
such territory are lost. Upon the Schleswig-Holstein banks the oysters 
are best when from about seven to eight years old. In warmer regions 
they become fully matured in a shorter time. 
The amount of increase in the length of oyster shells during a given 
time is very different upon different portions of the Schleswick-Holstein 
sea-flats, but their average growth in thickness is much more uniform; 
