342 U. S. BUREAU OF FISHERIES 
properly storing it until it reaches land. Plans also have been 
worked out for redesigning the methods of handling fishery products 
in the largest wholesale fish market in the country. 
The bureau has made a new and important contribution to the 
proper methods of handling fishery products through the issuance of 
a handbook on the refrigeration of fish (B. F. Document No. 1016). 
This contains a history of the industry and a discussion of important 
scientific principles involved; changes that take place in the fish im 
the fresh state and during freezing and holding; design, construction, 
and equipment of fish freezers; practical freezing methods; methods 
of brine freezing; transportation of frozen fish; and many other 
points essential to the proper understanding of the industry and 
its problems. 
That money properly spent in technological work brings large 
returns is evidenced by the bureau’s work on brine freezing. The 
bureau imported the first brine-freezing equipment into the United 
States and made the first demonstrations of this process. To-day 
brine freezing is being developed upon an extensive scale. 
Net preservation.—F¥ishing gear used by the fishermen in the United 
States is valued at about $14,000,000. It is probable that most of 
this gear must be replaced at least once in four years and much of it 
more often. It is evident that to increase the fe this gear would 
lower the cost of landing fish. Many fishermen are put to consider- 
able expense in having to remove growths that collect upon their 
netting when it is allowed to remain in the water. They must also 
keep extra gear to replace that removed for cleaning. At times bad 
weather prevents them from removing the netting, and during this 
time, frequently due to the heavy weight of fouling growths on the 
net, it is washed away by the storms. 
The bureau has attacked the problem of net fouling by marine 
growth and the preservation of the twine itself. This research 
work showed copper oleate to be an excellent preservative and anti- 
fouling agent and to have given excellent results commercially. 
There is need, however, for less expensive treatments that last longer. 
The bureau has developed new copper mixtures which are cheaper, last 
longer, and have proven excellent in commercial trials. This work is 
still in progress. The materials are being tried commercially by 
fishermen at several points in New Jersey and Virginia. In addition, 
over 70 new test lines, covering a wide range of chemical combinations 
are now being conducted at Beaufort, N. C. So far, these studies 
have been confined largely to salt water. Fresh-water fishermen 
have special problems with their nets, and it is hoped that this phase 
of the work can be taken up in the near future. 
Nutritive value of fish and shellfish—Research in recent years has 
shown fish and shellfish to have especially high nutritive values. 
The liver oils of certain fish, of which the cod is the most prominent 
example, are now our most valuable source of vitamins Aand D. A 
study by the bureau showed that sea foods are especially rich in 
iodine, being, in a great many cases, 50 to 200 times as rich in this 
important element as other common food products. They should be 
especially valuable, therefore, in the dietary as a preventative of 
goiter, many kinds of which have been proven to be due to the lack 
of sufficient iodine in food. The proteins of fish are of high quality. 
Information is lacking upon this important subject, however, and 
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