54 



U. S. BUREAU OF FISHERIES 



high during the first, second, and third months and results primarily 

 from overcrowding. Representative collectors taken from different 

 parts of the bay in September yielded by actual count 10,000 to 

 25,000 single seed oysters per partition. A week after the time of 

 setting, however, each partition was covered with as high as 100,000 

 to 200,000 spat, large numbers of which were gradually covered over 

 and smothered bj' the more rapidly growing individuals. In the 

 lower valves of the larger surviving spat there wei-e oftentimes found 



250 



200 



<c 

 tc 



UJ 



O, 



I- 

 < 

 Ol. 

 lO 

 Li- 

 O 



cc 

 to 



00 



2.5 



2.0 



1.5 



1.0 



A50NDJFMAMJJ 



MONTHS AFTER SETTING 



Figure 4. — Growth and survival of spat on oyster shells, Milford Harbor, 1925-26 



embedded many shells of the smaller individuals which they had 

 overgrown. By the first week in September the spat had attained 

 an average length of one-half to three-fourths inch and were some- 

 what elongated in shape as a result of crowding. At this age and size 

 the concentration of spat on the partitions ranged from 15 to 30 per 

 square inch. At a concentration of 20 or less it was found that each 

 individual spat was fairly well shaped and had developed sufficient 

 thickness of shell to withstand detachment and separation from the 

 collector and surrounding spat. At concentrations of over 20 per 

 square inch, the spat were decidedly overcrowded, the shells thin, 

 greatly distorted, and so closely ingrown with those adjoining as to 

 make detachment without" injury a difficult matter. It thus appears 



