COLLECTION OF SEED OYSTERS 57 



Since oyster shells are used more extensively than any other mate- 

 rial for collecting set it will be well to compare them in many re- 

 spects with partitions in order to show whether the latter are really 

 of practical value. One bushel of shells offers a surface of approxi- 

 mately 5,000 square inches but at least half of this is lost when the 

 shells lie on the bottom and sediment settles upon them. One parti- 

 tion has a surface of 1,000 square inches, all of which remains cle'an 

 because it lies vertical to the bottom. Two partitions are approxi- 

 mately equivalent to 1 bushel of shells in collecting surface, and each 

 has obtained, we shall say, a set of 10 to 20 spat per square inch. 

 By fall the crop of seed on each will be about equal except that those 

 on the partitions will be slightly larger as a result of being elevated 

 above the bottom. When the seed is dredged and shifted at an age 

 of 2 to 3 months the loss of spat on the shells will be approximately 

 2 to 5 per cent and about equal to that in separating the seed from 

 the partitions. Each material now has about 30,000 spat, but the 

 number on the shells decreases rapidly to 10,000 in six months and 

 finally to approximately 3,000 in one year as a result of overcrowd- 

 ing. The extent of loss in seed taken from the partitions w^ill 

 depend upon the skill used in detaching them and especially upon the 

 selection of clean hard bottom for their subsequent growth. In a 

 year we should have 20,000 to 25.000 single seed oysters from the 

 partitions as against a crop of 3,000 crowded individuals on shells. 



DISCUSSION AND SUMMARY 



The previous experiments have dealt with the problems of collect- 

 ing heavy oyster sets by the use of practical and efficient methods. 

 To increase the production of seed oysters in intensive setting regions 

 such operations and devices must be employed as will reduce crowd- 

 ing of the spat to a minimum. In order to prevent the loss of over 

 90 per cent of the spat by this cause, the setting must either be dis- 

 tributed over a greater amount of surface or the spat must be sepa- 

 rated from each other, preferably when they are 1 or 2 months old. 

 The oyster culturists clearly recognize that a well-distributed light 

 set of 10, or even 1 spat per square inch, is oftentimes more valuable 

 and productive of better seed oysters than are heavy sets. The fact 

 nevertheless remains that each small spat produced by a heavy set 

 is potentially equal to those from a light set, and the oyster farmer, 

 through inadequate methods, has permitted the loss of this valuable 

 product that would soon amount to millions of bushels of seed 

 oysters. This state of affairs has existed chiefly as the result of four 

 conditions, namely: (1) An insufficient supply of shells, (2) a limited 

 area of good setting bottoms, (3) ineffectiveness of heavy shell plant- 

 ings, and (4) the yearly fluctuation in setting on any particular area. 

 The research and practical experiments conducted by the bureau 

 during the past few years have served to furnish a solution to these 

 problems and to remove certain limitations. 



The supply of a suitable set-collecting material can now be in- 

 creased to meet any future demands by preparation during the 

 winter, of lime, cement, tar, or asphalt coated partitions. The pro- 

 duction of limited setting areas can be increased by the use of the 

 wire bag or partition type of seed collectors which make available 



