XII liEPOET TO THE SECRETARY OF COMMERCE 



setting, physiology of the oyster for experiments in seed-oyst«r pro- 

 duction and collection, and life history and biology of the oyster 

 drill. While these investigations were continued from last year, 

 new problems under the same headings have been taken up in addi- 

 tion. Surveys of oyster bottoms were made in Mobile Bay, Ala., 

 Mississipi^i Sound, Miss., Pamlico Sound, N. C, and various inshore 

 areas in Long Island Sound, and definite recommendations for im- 

 proving conditions on the beds and increasing the yield and the 

 quantity of the product were offered to the interested persons. 

 Special attention was given to the spawning and setting of oysters 

 in Long Island Sound. It has been found that water temperature 

 is the most important factor in controlling not only the development 

 and ripening of spawn but also the time of spawning. It has been 

 possible to predict, at least one month in advance, when spawning 

 will occur, when the greatest number of oyster larvae will attach 

 or set, and the relative intensity of the set in certain localities. This 

 information is most valuable to the oyster growers and advantage 

 was taken of tentative predictions in the summer of 1928. Further 

 study of the effects of currents on the distribution of the oyster 

 larvae and the means of controlling setting have been made and will 

 continue during the present summer. 



Study of the physiology of the oyster has been continued. The 

 effect of temperature on the oyster, its feeding and movements, with 

 its bearing on hibernation in northern water and the relation of 

 possible pollution to public health were investigated, together with 

 the study of the mechanism controlling spawning. The metabolism 

 of the oyster and the absorption of heavy metals under various con- 

 ditions are being investigated also. It was found that the green 

 substance is due to the absorption from the sea water of large quan- 

 tities of copper, and further experiments are being devised to dis- 

 cover means of prevention. The effects of chemicals, particularly 

 of chlorine, used in purification of the oyster, also were investigated. 

 It was found that relatively high concentrations were not harmful but 

 improved their keeping qualities during shipment and served to 

 remove disease bacteria from polluted oysters. 



Experiments in increasing the production of seed oysters succeeded 

 in increasing the yield at least ten times on the regular setting beds 

 and have made possible the collection of set on beds formerly unpro- 

 ductive. This was accomplislied through the use of wire-meshed 

 bags, in which oyster shells for catching the spat were placed on the 

 beds in piles so that attachment surfaces were provided above the 

 bottom in the zone where larvae are most abundant. In addition 

 to catching an abundant set, the bags permit the shells to be handled 

 more readily than by the old method of scattering them over the 

 bottom. Aloreover, the bags can be placed on bars that at present 

 can not be utilized otherwise. 



In the spring of 1928 an investigation of oyster-cultural methods 

 in Georgia, in cooperation with the State tidewater commissioner, 

 was undertaken in order to devise new means or adapt methods 

 developed in New England waters to conditions obtaining in the 

 South. The study of the life history and biology of the oyster drill 

 is virtually com})leted and a report has been submitted in which the 



