BUREAU OF FISHERIES 113 



physiological effects which these minerals may have on the animal 

 organism. For this reason an investigator, trained in pharmacology, 

 was assigned to the Bureau's technological staff several years ago. 

 Studies of the arsenic and copper content of shrimp and oysters, and 

 their physiological or pharmacological effect, have revealed that no 

 deleterious effects are observed as a result of eating tliese products 

 when these minerals occur in natural organic combination. Similar 

 studies are now being conducted on the natural fluorine content of 

 fishery products. 



Preservation of fshemj hyproducts. — During the year additional 

 data were obtained on the properties and composition of salmon oils. 

 A. simple method was develojDed for the commercial extraction of oil 

 from lean fish livers which do not give up oil by normal treatment. 

 Since the livers yielding the most potent vitamin oils come under 

 this classification, the value of such information can be appreciated. 

 The studies on liver oil extraction also led to practical suggestions on 

 methods for fortifying low- vitamin fish oils. Fish oils and oil- 

 bearing fishery products are subject to oxidative deterioration during 

 storage, and the matter of preventing such changes is an important 

 problem of the fishing industry. Further studies have been made 

 on the effectiveness of various materials for inhibiting oxidative 

 change. The oxidation of fat in fish meal causes it to become 

 insoluble in normal fat solvents. This leads to errors in analysis 

 and confusion when sales are based on analytical specifications. 

 Studies are being made to devise an analytical procedure which will 

 eliminate this clifiiculty. During the year the Bureau published 

 a report on the distribution of vitamins in salmon cannery waste and 

 contributed papers to scientific and trade magazines covering such 

 subjects as the utilization of salmon cannery waste, cereal flours 

 as antioxidants for fishery products, and the determination of fat 

 in fish meal. 



Fish cookery. — During the past year, the Bureau continued the 

 development and testing of recipes for the preparation and cookery 

 of fish and shellfish, and carried on practical demonstrations in fish 

 cookery in cooperation with home economics workers and others in 

 various parts of the country. In cooperation with the Federal Sur- 

 plus Commodities Corporation, some practical demonstrations in 

 fish cookery were conducted for relief workers and others interested 

 in connection with the distribution of fish to persons on relief rolls. 



BIOLOGICAL FISHERY INVESTIGATIONS 

 IXVESTIGATIONS OF COMMERCIAL FISHES 



North Atlantic fi-sher'y investigation.^. — Biological studies in the 

 North Atlantic area are concerned chiefly with changes in abundance 

 of the stocks of fish which support New England's extensive and 

 varied fisheries. Specific problems investigated during the year 

 dealt with the causes of the extreme fluctuations in abundance of 

 mackerel and means of predicting such fluctuations; the relation be- 

 tween the existing stocks of haddock and the strain imposed by the 

 present intensive fishery; the economic and biological significance of 

 the extension of otter trawling to include several species in addition 

 to cod and haddock; and the condition of the flounder fisheries in 

 coastal waters from Massachusetts to New York. 



