206 
BULLETIN OF THE BUREAU OF FISHERIES 
cultch planted, thereby increasing the area suitable for attachment, and by utilizing 
the three dimensions of the setting zone by planting shells in bags or crates. A 
study of the distribution of the setting zones in various localities reveals the fact 
that there is always a level or zone where setting is the heaviest. The question of 
what causes the oyster larvse to set in a definite zone is a very complex one and 
requires further investigations; but the determination of the zone of setting in any 
given locality presents no difficulty, as in most of the cases a careful examination 
of the bottoms and various submerged objects or structures allows one to determine 
it very accurately. (Fig. 3.) Obviously this zone should be utilized to its maximum 
capacity. 
It is known that setting in northern waters is rather irregular; good years are 
followed by blank ones when there is no setting at all or when it is so light as to be 
of no commercial value. Examination of the setting regions discloses, however, the 
fact that there are certain localities where setting occurs regularly every year. Such 
are, for instance, Onset Bay and Wareham River in Massachusetts. It is logical 
that these areas should be more thoroughly utilized for the production of seed oysters. 
In the localities where setting continues for a period of 2 or 3 weeks, the collectors 
which had already caught a sufficient number of spat can be replaced by new ones, 
and in this manner the productivity of the given area may be increased and the 
intensity of setting on the cultch can be regulated. 
One important factor governing the propagation of oysters is frequently for- 
gotten or overlooked. It is the presence of a sufficient number of adult oysters 
(spawners) in the vicinity of the setting grounds. It is. obvious that the abundance 
of spat is primarily dependent on the quantity of eggs discharged into the water. 
Inasmuch as the fertilization of the oyster egg takes place outside of the organism 
and is a matter of chance, there must be a sufficient number of ripe males and females 
to insure the abundance of the oyster larvse in a given body of water. It is estimated 
that the spawning bed should contain not less than 500 bushels of spawners per acre. 
Spawning and setting of oysters are controlled by a great number of environ- 
mental factors of which the temperature, salinity of the water, and the tidal currents 
are of great importance. Hence, knowledge of these conditions is essential for the 
success of an experimental study of oyster culture. In the following papers consider- 
able space is given to the description of the localities where the experiments were 
carried out, together with the records of temperature, salinity, and velocity of tidal 
currents. These experiments were carried out under the general direction of P. S. 
Galtsoff in Wareham Kiver, Mass., in Onset Bay, Mass., in Milford Harbor, Conn., 
and in Great South Bay, N.Y. These localities represent the different ecological con- 
ditions which one encounters in the northern section of the Atlantic coast. It was 
the author’s intention to give a fair trial to the new method of spat collecting and 
to determine by a comprehensive study both its advantages and limitations. 
The experimental work was greatly facilitated and in many instances made possi- 
ble by the excellent cooperation given by the oystermen. It is a pleasure to express 
our thanks and to acknowledge the help rendered by W. H. Raye, president, and 
Capt. C. E. Wheeler, manager, of the Connecticut Oyster Farms Co., and to Messrs. 
Schroeder and Besse, of Onset, Mass. 
