30 THE OYSTER x\XD THE OYSTER INDUSTRY. 



is little movement, especially in inclosed bays or the like, the deposit 

 accumulates upon the shells rapidly. Such waters, while often very 

 desirable for growing or fattening oj^sters, are for this reason poorly 

 adapted to catching set. 



It early became apparent, then, that it would not suffice merely to 

 spread the cultch at any season of the year most convenient to the 

 planter. Cidtch should be put do^^^l just as shortly before the bulk 

 of the free-swimming larvae peaches setting time as it is possible to 

 do it. In general this has been ascertamed by experience in the 

 various regions where this method is practiced. For example, in 

 Great South Bay it is planned to complete ''shellmg" by July 1. In 

 Long Island Somid shelling oft(>n begms immediately after the 

 Fourth of July and is completed early in August, individual planters 

 having different ideas as to the l^est time for planting cultch. In 

 Louisiana cultch is put down in June. 



In the case of the large oyster firms, owing to the great quantity of 

 shells handled, it is impossible to concentrate all the shellmg into a 

 few days preceding setthig time. Such firms often require a month 

 or six weeks in wliich to complete the process. The best that can be 

 done is to make this period coincide with the weeks immediately pre- 

 ceding setting time. 



The proper time of year for planting the cultch has been fixed ap- 

 proximately at certain seasons for each locality, largely by experience 

 derived from the results of some years' practice in this method. The 

 appearance of the adult spawning oysters is noted at intervals each 

 year and the time of plantiiig varied a few days or weeks one way or 

 the other. The aim has mainly been to have the cultch down before 

 any appreciable quantity of spawn has been thi'own out by the oysters. 



It has been thought until relatively recently that the oyster larvae 

 set within 3 or 4 days after the spawn was thro's\Ti out. It is now 

 known that from 14 to 18 days elapse in New Jersey waters and 

 northward, and a somewhat shorter period in the warmer waters of 

 the Southern State's. With this longer period in mind, it will be seen 

 that the time of setting is at least two weeks su1)sequ(M\t to the throw- 

 ing out of the spawn. In case the spawnmg ])eriod is extended over 

 several weeks, the problem is complicated. In the more northern 

 waters, especially in Long Island Sound, the spawning period has 

 been found to be short, hardly more than two weeks in length, the- 

 bulk of the spawn being tliroAvn out in the course of a few da3^s. In 

 such case, keeping in mind the two weeks free-swimming period of tlii^ 

 larvae, it is possible to judge the time of putting down cultch quite 

 accurately. 



Since seasonal variations affect the time of spawning, it follows 

 that no exact date which will hold good for each year can be set 

 for planting cultch. iVs a result of a survey of the free-swimming 

 larva', made by the Bureau of Fisheries, it was found that the setting 

 time of the bulk of the larvae in Long Island Sound in 1918 occurred 

 during the week of August TO to 17. In 1919 there was no setting 

 time in Long Island Sound, since no larvae developed to setting size, 

 owing, doubtless, to the a])normally low temperature of the water. 

 In 1919, in Great South Bay, setting began about July 1, but the 

 bulk occurred July If) to 17. These data were secured by following 

 the development and mo\'einents of the free-swimming larvae by 



