22 REPORT OF THE COMMISSIONER OF FISHERIES. 



receive permit infections by bacteria and " fungus," which often 

 result in death. It has been discovered that this difficulty may 

 be overcome by immersing the fish in a solution of copper sulphate 

 after the encystment of the glochidia. The latter are not injured 

 by the treatment. 



The recommendations of the bureau for extending protection to 

 mussels having been given effect by a number of the States, some 

 of the closed areas have been placed under systematic observation 

 to determine the results. The condition of the beds has been de- 

 termined with respect to the abundance and ages of shells of dif- 

 ferent species for comparison with similar data to be collected five 

 years hence. 



An examination of the records of the catch of mussels on White 

 Eiver, Ark., over a period of years has confirmed the observations 

 of mussel buyers on the stream that the artificial propagation of 

 the yellow sand-shell on the river a number of years ago has re- 

 sulted in a material increase in the production of that valuable 

 shell. 



OYSTER INVESTIGATIONS. 



The grave difficulties with which the oyster industry has had to 

 contend in recent years, particularly in Long Island Sound and on 

 the south wash of Long Island, have continued to receive the bureau's 

 attention. 



In Long Island Sound the set of young oysters has never been 

 regular within historic times, but until recently it occurred with 

 sufficient frequency to permit the upbuilding of the most extensive 

 oyster-cultural operations in the country. This region is on the 

 minimal temperature verge of the oyster's habitat, and the investiga- 

 tions made by the bureau have now shown that a water temperature 

 suitable for spawning and the development of the oyster larvae is 

 attained for but a short time each year. In the summer of 1921 

 this te^iperature was reached exceptionally early, but this condition, 

 which ordinarily would have been favorable, was interfered with 

 by subsequent cold, rainy weather, during which the larvae disap- 

 peared. 



The inshore, shoaler, warmer waters, which formerly supported 

 the natural beds furnishing the spat that seeded the planted beds 

 in the colder deep waters of the sound, have been largely depopu- 

 lated by pollution with trade wastes. The solution of the problem 

 appears to lie in planting and maintaining spawning beds in shore 

 waters not yet seriously contaminated and in reducing the pollution 

 now existing in other areas. The Avork in Great South Bay re- 

 vealed an early occurrence of spawning and a great abundance of 

 oyster larvae widely distributed, and, later, a correlated abundance 

 and distribution of young oysters on the planted shores. Still later 

 practically all of this set died, and the investigator is of the opin- 

 ion, although it was not possible to demonstrate it as a fact, that 

 this mortality was due either to the generation of toxic gases or the 

 exhaustion of oxygen by the organic matter in the bottom mud. 

 It was observed that the oysters that had set on materials ex- 

 perimentally raised above the bottom survived, and the investigator 

 has suggested to the planters that a similar method be tried com- 

 mercially during the season of 1922. 



