OYSTERS AND METHODS OF OYSTER-CULTURE. 305 



but other objects accideutally dropped overboard would often, when 

 recovered a few weeks later, show a heavy set of spat. Naturally they 

 began to throw objects into the water for the express purpose of 

 collecting- the spat and thus increasing the amount of seed available 

 and from this beginning the present system of spat-collecting now in 

 use in our waters was developed. 



For this method of planting it is, of course, essential that there 

 should be in the vicinity of the beds spawning oysters, either of volun- 

 teer growth or planted, and that the temperature of the water should 

 be between 68° and 80° F. during a period of some weeks' duration. 



PREPARING BOTTOM. 



The bottom used for this method of cultivation should be firmer than 

 that which will suffice for bedding well-grown seed, though soft bottom 

 may be prepared so as to be satisfactorily used. If the bottom is very 

 soft it may be overlaid with gravel or sand in the manner before 

 described (p. 300), and upon this the collectors or cultch may be depos- 

 ited. In a moderately soft bottom the cultch can be applied without 

 previous preparation other than to clear the ground of all debris which 

 would interfere with working it. Hard, gravelly bottom in shoal water, 

 which may be of little use for the raising of adult oysters on account 

 of the absence of food, may prove an excellent place for the collection 

 of spat, and the same may be said of some places with a stiff clay soil. 



One of the great difficulties in spat-collecting is to avoid the deposit 

 of sediment upon the cultch, as an amount of sedimentation which 

 would have no effect whatever upon the adult oyster would prove 

 absolutely fatal to the young spat. At the time of attachment the 

 infant oyster is about one-ninetieth of an inch in diameter, and the 

 deposit of a very slight film either before or immediately after the 

 falling of the spat would be sufficient to cause its sufibcation. It will 

 be seen, therefore, that a soft bottom upon which the large oysters will 

 thrive, or an amount of sedimentation which may favor the rapid growth 

 of the adults from the food matter which it contains, will effectually 

 prevent, in many instances, the cultivation of spat. 



CULTCH, COLLECTORS, STOOL. 



By these terms is understood any firm and clean body placed in the 

 water for the i^urpose of affording attachment to the spat or young 

 oyster. A great variety of objects have been suggested and used for 

 this purpose, both here and abroad, and some of these will be now 

 discussed. 



Oyster shells. — In this country oyster shells are the oldest and most 

 generally used form of cultch. They are usually merely spread upon 

 the bottom, being thrown broadcast from boats in the manner which 

 is described for planting seed oysters (p. 302). When the bottom is 

 sufficiently liard to prevent the submergence of the shells, it is custom- 

 ary to Sipj-ead them as uniformly as possible over the ground, so as to 



r. C. R. 1897 20 



