COLLECTION OF SEED OYSTERS 55 



that a set of less than 20 spat per square inch would be the concentra- 

 tion most desirable on collectors from which they are to be detached 

 in approximately two months. The only practical method of limit- 

 ing the intensity of setting under such conditions is by stacking of 

 shells or partitions so as to offer more surface for attachment of the 

 oyster larvae. 



The detachment of spat from the South Bay collectors was in some 

 instances automatically brought about by disintegration of the col- 

 lectors, but in most cases required hand labor. The partitions were 

 broken up by tearing apart each cardboard strip, by hitting the col- 

 lectors against some solid object, or by slipping a broad, sharp knife 

 under the spat or cement. The loss of spat from these operations 

 ranged from approximately 2 to 5 per cent and depended largely 

 upon the concentration per square inch. Spat which are growing 

 vertically to the surface of the partition can be separated easily with 

 minimum loss. Those that are lying flat are difficult to detach with- 

 out injury and should be planted by tearing the partition into squares 

 at each joint. Though the present methods of spat detachment and 

 separation are comparatively crude, they do demonstrate that seed 

 oysters can be successfully removed from such collectors when a few 

 months old. During the coming summer further experiments will 

 be made to improve the size, shape, and coating of the partitions and 

 determine the most desirable specifications for use in accordance with 

 conditions in different localities. 



In Milford Harbor the partitions were either set out directly on 

 hard bottom or shells or were elevated a few inches in groups of four 

 by means of stakes. A very light set occurred the first week of 

 August, ranging from 75 to 200 spat per collector, followed by a 

 greatly delayed heavier set on September 14 to 18, of approximately 

 1,000 to 2,000 spat per collector. Because of the slow growth and 

 lateness of this set very few observations or conclusions on these ex- 

 periments can be made until next spring. A few dozen partitions 

 were coated with hot asphalt to which small bits of oyster shell were 

 made to adhere, and these were found to have collected nearly as 

 many spat as the cement-coated type. 



It might be well to point out here another advantage in obtaining 

 separation of the seed oysters when a few months old as demonstrated 

 by experiments in Milford Harbor in 1928 and 1929. A set averag- 

 ing 60 spat per shell was obtained on new oyster shells and also on 

 old, thin, fragile shells that were excavated from deposits in the 

 Housatonic River. A year later the new shells were covered with 

 20 to 25 closely crowded seed oj^sters, while those on the old shells had 

 broken apart and were lying about singly on the bottom. By measur- 

 ing the displacement of several representative samples it was found 

 that 25 of the single seed had a total volume in one year of 14.5 cubic 

 inches while the same number when crowded on a shell had a volume 

 of only 7.8 cubic inches. In other words, there is nearly 100 per 

 cent increase in volume and growth to be gained during the first year 

 by the early separation of seed. The shell which they produce is also 

 much thicker, much heavier, and nearly round in shape and will with- 

 stand rough treatment in dredging and transplanting operations. 



