■- PROGRESS IN BIOLOGICAL INQUIRIES, 1929 1111 



Liuj^eiuouth black bass, crappie, blue*?!!!' sunfish, bullheads, and 

 ^'oldfish were used in these experiments, and it was found that the 

 Hsh were not injuied api)ieeiably by a concentration of arsenic 

 trioxide as hi<i:h as 7 parts per million. Since the fish were kept in 

 these liiirh concentrations of arsenic foi' several days without injury, 

 it is apparent that no dan«;cr to the Hsh need be anticipated from 

 the use of arsenic in concenti'ations sufficient to kill vegetation. 



OYSTER INVESTIGATIONS 



Oyster investi<rations carried out under the direction of Dr. Paul 

 S. (ialtsotf durintr 1929 consisted in the experimental study of oyster 

 culture in New Enrjland, Georjjjia, Texas, and Washinfrton; in a 

 .study of the physiolojry of adult and larval oysters; in the survey 

 of the oyster bottoms of the States of Alabama and Delaware; in a 

 study of the effect of pulp-mill wastes on oysters in Puget Sound; 

 and in an investigation of the biology of the natural enemies of the 

 oyster — the 03'ster drill and the starfish. 



EXPERIMENTAL STUDIES IN OYSTER CULTURE 

 NEW TYPE OV SEED-OYSTER COLLECTTOR 



Experiments carried out by H. F. Prytherch in cooperation with 

 the l^luepoints Co. and the Connecticut Oyster Farms Co. have re- 

 sulted in the development of a practical and efficient method for 

 collecting and transplanting heavy or intensive oyster sets. 



In certain oyster-growing regions, such as South Bay, Long 

 Island, and the tidal flats in the South Atlantic States, the setting 

 of oysters is often so intensive that a high percentage of the spat 

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

 are so closely cemented together and misshapen as to be of little value 

 as seed oysters. A cheap collector for use under such circumstances 

 Avas devised by Prytherch in 1928. consisting of cardboard egg-crate 

 partitions which were covered Avith either i)araffin and coarse sand or 

 asphalt. The final step in perfecting this type of collector and mak- 

 ing it of practical value is credited to W. H. Raye. president of the 

 North Atlantic Oyster Farms, who used a coating of lime, cement, 

 and sand which has improved the collector in many respects. By 

 covering the cardboard with this mixture, we have essentially a 

 series of compartments lined with a thin layer of shell-like substance 

 which has been found suitable for collecting thousands of spat and 

 holding them until they are large enough to be broken apart and 

 separated as single seed oysters. 



During the past summer 2,000 set collectors of this general type 

 were tested out in South Bay, Long Island, and Milford Harbor, 

 Conn. The size of the collector was increased so as to consist of 25 

 compartments giving a total of approximately 1,000 square inches 

 of surface per collector. In South Bay the setting was quite heavy 

 and covered almost every collector with from 50 to 200 spat per 

 square inch of surface. By comparing the growth and survival of 

 spat on the partition collectors Avith those attached to oyster shells 

 on the same area, tlie superior value and efficiency of the new method 

 can be seen. 



