4 U. S. BUREAU OF FISHERIES 



Shell-fisheries. — Oyster investigations during the year added to the 

 physiological and ecological knowledge on which successful oyster 

 culture is based. In the New England section there was inaugurated 

 the important service of predicting the time and relative intensity 

 of spawning and setting, thus enabling growers to plant their shells 

 at the proper time to obtain the maximum set of larval oysters. 

 Studies on the starfish demonstrated clearly that the control of this 

 destructive enemy of the oyster is an interstate problem and that more 

 effective and better coordinated measures must be taken for its 

 eradication. Experiments looking toward chemical control of star- 

 fish have progressed to such a point that their practical application 

 during 1938 seems assured. Additional evidence has been secured of 

 the detrimental effect of pulp-mill effluent on shellfish. Studies of 

 the precise nature and physiological effect of the effluent will be of 

 great assistance in any efforts that may be made to remedy this pol- 

 lution hazard. Ecological surveys made by the staff' in Long Island 

 Sound, Virginia, North Carolina, Alabama, and Florida have been 

 used by State conservation authorities for the protection and improve- 

 ment of shellfish resources of the coast. During the year a new 

 laboratory was established at Pensacola, Fla., to serve as headquarters 

 for oyster investigations of the Gulf area. 



Fresh water -fisheries. — In recognition of the critical need for a 

 broader basis of scientific fact to direct the rapidly expanding fish 

 cultural operations throughout the country, investigations of the 

 aquicultural staff have been directed in particular toward the de- 

 velopment of new and more effective methods, both in the rearing and 

 stocking of fish. The continued operation of test streams in Vermont 

 lias demonstrated the value of this procedure as a yardstick for 

 measuring the success of stocking in trout waters. The Pisgah Na- 

 tional Forest in which an experimental project has now been under 

 way for more than a year provides an excellent natural laboratory 

 for the application and testing of fish management practices. Here 

 studies are under way to determine the size of fish and the intensity 

 of stocking which produce most satisfactory results and to test the 

 effect of various types of stream improvement on the production of 

 fish and food organisms. Through the operation of experimental 

 streams in California, data are being collected on the survival rates 

 of hatchery trout planted at various ages and under varying predator 

 conditions. The accumulation of such information over a period of 

 years will serve as a definite guide for stocking programs. 



In the fundamental nutrition studies which have been continued at 

 Cortland, N. Y., current hatchery feeding practices are being im- 

 proved through the testing of a great variety of products. Through 

 biochemical and pliysiological studies, an attack has been made on 

 the important problem of so adjusting the growth rate of hatchery 

 fish that the most desirable physical development will be produced. 



Because fish management practices as applied to bass have received 

 little attention from fish culturists in general, fundamental problems 

 in this field remain unsolved. Determination of the effectiveness of 

 natural propagation, which in the case of bass may prove to be more 

 efficient than artificial propagation, is obviously a first consideration. 

 Observations on the time of spaw^ning, the production of fry, and 

 the food and growth of the young bass have therefore been conducted 



