30 THE OYSTER AND 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 oysters, are for this reason poorly 

 adapted to catching set. 



It early became apparent, then, that it would not suffice m.erely to 

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

 planter. Cultch should be put down just as shortly before the bulk 

 of the free-swimmmg larvae reaches settmg time as it is possible to 

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

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

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

 Long Island Somid shelling often begins immediately alter the 

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

 having different ideas as to the best 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 setting time. Such firms often requke a month 

 or six weeks in which 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 plantmg the cultch has been fixed ap- 

 proximately at certain seasons for each locality, largely by experience 

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

 appearance of the adult spawning oysters is noted at intervals each 

 year and the time of planting 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 thrown out by the oysters. 



It has been thought until relatively recently that the oyster larvae 

 set within 3 or 4 clays after the spawn was thrown 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 States. With this longer period in mind, it will be seen 

 that the time of settmg is at least two weeks subsequent to the throw- 

 ing out of the spawm. In case the spawning period is extended over 

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

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

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

 bulk of the spawn being tlirown out in the course of a few days. In 

 such case, keeping m mind the two weeks free-swimming period of the 

 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. As a result of a survey of the free-swimming 

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

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

 during the week of August 10 to 17. In 1919 there was no setting 

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

 owing, doubtless, to the abnormally low temperature of the water. 

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

 bulk occurred July 15 to 17. These data were secured by following 

 the development and movements of the free-swimming larva? by 



