314 REPORT OF THE SECRETARY OF THE INTERIOR 
in these rivers. Annual surveys are also made of the catch of ale- 
wives in the Potomac River. 
Canned fishery products and byproducts.—Since 1921 annual sur- 
veys have been made to collect statistics on the production of canned 
fishery products and byproducts of the United States and Alaska. 
These data are of importance to the industry as a guide in their manu- 
facturing activities. This information is published annually. 
Cold-storage holdings of fish—Through the cooperation of the Agri- 
cultural Marketing Service, Department of Agriculture, statistics are 
collected and published monthly on the cold-storage holdings of fish- 
ery products and quantities frozen by important species or groups 
of species. These figures are shown separately for major geographi- 
cal sections. Since holdings of fishery commodities in cold storage 
represent a considerable portion of the available supply of fishery 
commodities on hand at any one time, these data are eagerly sought 
by the fishery industry. Monthly cold-storage bulletins are published. 
Sponge market, Tarpon Springs, Fla—The domestic sponge fishery 
is confined to the State of Florida, and a large part of the production 
is sold through the Sponge Exchange at Tarpon Springs. In view 
of the importance of this exchange in the total domestic sales transac- 
tions of the industry, the Bureau obtains and publishes statistics of 
the quantity and value of sponges by variety classifications which are 
handled through the exchange each year. 
TECHNOLOGICAL INVESTIGATIONS 
The principal objective of fishery technological investigations is 
to increase the economic value of the aquatic harvest by more com- 
plete and efficient utilization. Toward this end studies are conducted 
of the technical phases of fish production, processing, and marketing. 
In planning these studies efforts are made to select those which have 
the broadest fundamental application. The value of technologica! 
investigations does not end with their application to the fishing indus- 
try, as other American industries also make extended use of the results 
of this work. For example, the Bureau pioneered in this country in 
the development of quick-freezing methods as adaptable to the preser- 
vation of fishery products. These methods now have widespread ap- 
plication in the preservation of fruits, vegetables, poultry, and meat. 
In another instance, a search for new sources of vitamins A and D 
was conducted and it was found that oils from many species of fish 
are rich in these vitamins. A direct outgrowth of these investigations 
is the production of oils having a high vitamin content from the livers 
and viscera of various species of fish such as halibut, tuna, and sword- 
fish. This work has resulted not only in raising the income of the fish- 
