BUREAU OF FISHERIES 97 
concerning the role or effect of mineral constituents as they naturally 
occur in fishery products, as compared with these same minerals in 
inorganic form, on metabolism in both human and animal nutrition. 
Such studies on arsenic and copper, which included tests not only on 
experimental animals, such as albino rats, but also included clinical 
tests with humans, have been published by the Bureau. These tests 
showed that arsenic, which occurs in shrimp in a stable, undissociated, 
organic state, is readily soluble in water and is rapidly eliminated by 
the kidneys. 
Preservation of fishery byproducts—tIn this field the Bureau’s 
technologists studied the utilization of salmon cannery waste, the 
extraction of oil from halibut livers and fish livers of similar type, 
methods for preventing or retarding the development of rancidity in 
fish and fish-liver oils, the place of oily fish meals in animal feeding, 
studies of methods for determining the fat content of fish meal, and 
the development of methods for the chemical preservation of fish 
waste. Developments in the preservation of fishery byproducts have 
yielded results of great economic value both to the fishery industries 
and to the agricultural industries, as fish oils and fish meals, kelp 
meal, oyster and clam shell products, etc., are becoming of increasing 
economic value to the farmer in providing to him for the livestock 
ration feed concentrates of unexcelled nutritive properties. 
Nutritive value of aquatic products —This is also a most important 
phase of technological investigations, since the ultimate nutritional 
value of finished aquatic products, ready for consumption, is the only 
true yardstick for evaluating improvements and advancements in the 
utilization of fishery products and byproducts for human and animal 
nutrition. Among the major projects in nutrition occupying the tech- 
nological staff during the past year were studies of the vitamin po- 
tency of fish-liver oils, the further development of menhaden fish oil 
for poultry feeding, studies of the vitamin content of fresh fish flesh, 
the value of menhaden fish meal as an ingredient of the dairy ration, 
summary or compilation of literature on the nutritive value of shell- 
fish, studies of the chemical composition and nutritive value of fish 
proteins, and of mineral constituents in fishery products and 
byproducts. 
Fish cookery.—tIn the fish-cookery laboratory there have been con- 
tinued the development and testing of recipes for the preparation of 
various fishery products. During most of 1936, however, the Bu- 
reau’s fish cookery expert carried on educational work and practical 
demonstrations in the preparation and cooking of fish and shellfish 
at schools, women’s clubs, and various other gatherings. As a result 
of this work considerable interest has been stimulated among the 
public in fish cookery and in the food value of fishery products. 
BIOLOGICAL FISHERY INVESTIGATIONS 
The program of biological investigations pursued by the Bureau 
of Fisheries during the fiscal year 1937 followed three major lines of 
endeavor: (1) population studies of commercial and game fishes to 
measure the effect of fisheries of known intensities, to determine the 
effectiveness of various conservation measures, and to devise methods 
of managing or controlling the fisheries so as to maintain a self- 
sustaining level of population abundance; (2) management of in- 
