18 U. S. BUREAU OF FISHERIES 
The project on freezing oysters in the Bureau’s Seattle laboratory 
and in the Seattle laboratory of the Buredu of Chemistry and Soils 
was carried on by Dr. Francis P. Griffiths, junior bacteriologist, under 
the supervision of Roger W. Harrison, associate technologist in charge, 
with the assistance of H. C. Diehl, in charge of the Bureau of Chemis- 
try and Soils laboratory. 
ELECTROMETRIC TESTS FOR THE FRESHNESS OF FISH 
During the early summer months of 1936 one of the large firms pack- 
ing frozen fish became interested in the possibilities of the commercial 
application of the electrometric method for determining the relative 
freshness of haddock, cod, and pollock developed by M. E. Stansby 
and J. M. Lemon of our staff. This method has been described in 
detail in previous annual reports ef this Division and was originally 
published in a separate report.’ This firm is interested in making use 
of this method for determining quality or relative freshness in its 
purchases of the above-mentioned species of fish and requested the 
Bureau to send one of its technologists to give its chemists a practical 
demonstration of the usefulness of the method. M. E. Stansby was 
assigned to this demonstration for a period of 2 weeks. During this 
time he instructed one of the chemists in the employ of the company 
in the method of making these tests. Several modifications of the 
method were developed which show considerable promise for applica- 
tion in large-scale operations for classifying fish as to auality or relative 
freshness. In the contmercial test fish were selected on the basis of 
the test, frozen, and placed in cold storage, and samples later were 
examined from time to time to determine the keeping qualities of the 
various grades as shown by the electrometric test. This demonstra- 
tion indicated that it is possible to use this test commercially to deter- 
mine the quality of fish and further emphasized the fact that only 
first-quality fish should be frozen if it is to remain in cold storage for 
any length of time. 
STUDIES OF RANCIDITY IN FISH 
In this field attention was concentrated on the development of 
methods for retarding oxidation or rancidity of the oils in fatty fish. 
Boston mackerel was used in the experimental work. In commer- 
cial practice oxidation of the body oil of this fish makes it difficult to 
keep it in first-class condition when held in cold storage. 
In this study it was observed that considerable variation occurs in 
the quantity of oil contained in individual mackerel taken at a certain 
season. There is also a variation with the season. Seasonal varia- 
tions, however, occur to a greater extent in the larger fish, while there 
seems to be a fair degree of consistency in the oil content of the smaller 
fish of this species throughout the season. This may be illustrated 
by one set of the samples examined at the beginning of the season in 
April. The large size fish had an oil content of only 2 percent in the 
flesh. As the season progressed the oil content of other fish examined 
increased and by the latter part of August it mounted to approxi- 
mately 20 percent. It then began to decline until it had gone down 
to approximately 8 percent at the end of the season in December. 

3 “An electrometric method for detection of relative freshness of haddock’’, by Maurice E. Stansby and 
James M. Lemon, U.S. Bureau of Fisheries, Gloucester, Mass. Reprinted from Analytical Edition, In- 
dustrial and Engineering Chemistry, vol. 5, p. 208, May 15, 1933. 
