IMPROVED METHODS FOR THE COLLECTION OF SEED OYSTERS 



IJy HEKJiKirr V. I'i;ythki!(:h 

 Assistant Aquatic Biologist, United States Bureau of Fisheries 



CONTENTS 



Page 



Introduction 47 



Wire-bag collectors 49 



Experiments with partitions 52 



Discussion and summary 57 



INTRODUCTION 



In order to devise new methods for maintaining and increasing the 

 supply of oysters, the Bureau of Fisheries has conducted extensive 

 studies and experiments under the direction of Dr. P. S. Galtsoff, in 

 Massachusetts, Connecticut, New York, and various other coastal 

 States. Two practical methods have been developed for increasing 

 the production of seed oysters, since the decrease in the supplj^ of 

 these has been one of the principal causes for the decline of the indus- 

 try. In the propagation and cultivation of oysters the most important 

 operation is that of collecting the seed oysters, or spat, on some suit- 

 able material such as shells, gravel, brush, etc. The usual practice is 

 to clean and prepare an area of bottom in the vicinity of the spawn- 

 ing beds and plant thereon from 500 to 1,000 bushels of oyster shells 

 per acre. The oyster larvse when fully developed cement themselves 

 or set upon these shells and though designated as set, or spat, are in 

 reality small seed oysters, as they grow and develop into the adult. 



The quantity of seed oysters that is obtained on the shells varies 

 greatly according to seasonal conditions, number of spawners, and 

 especially the location of the bottoms on which the shells are planted. 

 In nearly every oyster-growing region there are certain areas or zones 

 where the setting is of greatest intensity, and more seed oysters are 

 produced than can survive and grow on the surface that is avail- 

 able. For example, in some of these areas we oftentimes find on 

 a single oyster shell from a few hundred to several thousand spat 

 while only 25 or 30 of these are able to survive. With such intensive 

 setting, a very high percentage (98 to 99.9 per cent) of the spat die 

 from overcrowding, lack of food, oxygen, etc. ; and those surviving 

 are so closely cemented together and misshapen that they are of 



^Appendix IV to tlie Report of the U. S. Commissioner of Fisheries for 1930. B. F. 

 Doc. 1076. 



0G420— .30 47 



