PRODUCTION AND COLLECTION OP SEED OYSTERS 
221 
It is interesting to compare the setting in the crates with the setting on the 
shells (beds A and B, fig. 13). The beds are separated by only a few feet; they 
were mapped and divided into 7 areas comprising 50 squares, from which samples 
of shells were taken. The number of spat on the bed was determined by counting 
them on both surfaces of 10 shells taken at random from the top layer and from 10 
shells at a deeper layer of the bed. It was noticed that there were many more spat 
on the upper layer of cultch than there was in its deeper layer. This can be seen in 
Table 10. 
Table 10 . — Number of spat in top layer and in deeper layers of shells on shell beds 
Square No. 6 
Average num- 
ber of spat per 
square inch of 
shell 
Square No. G 
Average num- 
ber of spat per 
square inch of 
shell 
Square No. 6 
Average num- 
ber of spat per 
square inch of 
shell 
Square No. 6 
Average num- 
ber of spat per 
square inch of 
shell 
Top 
layer 
Deeper 
layer 
Top 
layer 
Deeper 
layer 
Top 
layer 
Deeper 
layer 
Top 
layer 
Deeper 
layer 
Shell No. 1-. 
13 
0 
Shell No. 4.. 
4 
2 
Shell No. 7.. 
3 
0 
Shell No. 10, 
14 
1 
Shell No. 2.. 
12 
1 
Shell No. 5.. 
12 
0 
Shell No. 8.. 
8 
0 
Shell No. 3.. 
9 
1 
Shell No. 6.. 
9 
3 
Shell No. 9.. 
8 
0 
In order to facilitate comparison, all the squares from which samples were taken 
were grouped in 7 large sections (fig. 13, A-G), and the average number of spat per 
bushel of shells was computed for each section separately. The intensity of setting 
over the beds varied from 7,632 spat per bushel in section A, located close to the fourth 
row of crates, to 20,624 in section D. The average intensity for both beds was 15,472 
seed per bushel, approximately the same as that obtained in the fourth row of crates 
(15,058 per bushel). It should be borne in mind that oyster shells were planted in 
the crates, while scallop shells were scattered over the beds. The number of scallop 
shells per bushel is about 2% times that of oyster shells; hence, because of the greater 
surface area exposed for the attachment of larvse, the setting should be heavier on the 
former than on the latter. For practical purposes there is no advantage, however, 
in increasing the intensity of setting. In the case of oyster shells, a uniform set 
amounting to 3,000 spats per bushel can be regarded as an acceptable minimum. 
For fragile scallop or jingle shells, the figure should be higher. 
The problem consists in increasing the productivity of seed oysters without 
increasing the intensity of setting. The comparison of setting in the crates with that 
on the bed should refer, therefore, not to the volumes of shells used, but to the unit of 
area over which shells or crates are planted. Each crate covers an area of 2 square 
feet, and a comparison of the number of spat found over this area on the bed with the 
number of spat in the crates gives us a true idea of the efficiency of the crate method. 
In order to make such a comparison, it is necessary to know the number of scallop 
shells planted over a unit area of the bed. It was found that on the average there 
were 86 scallop shells on each square foot of the bed and that 318 scallop shells formed 
one peck. Taking these figures as representative of the size of shells and the density 
of planting in Wareham River, we find that there were 0.27 pecks of shells planted on 
each square foot of the bed, or 0.54 pecks on each 2 square feet. Calculated on this 
basis, the number of spat per unit of 2 square feet in different sections of the bed is 
given in Table 11. 
