BUREAU OF FISHERIES 83 



contrar}' to the <^eiieral belief neither smoke nor salt brine has a 

 preservative effect on fish so preserved in ordinary commercial prac- 

 tice. In this work the technologists have been able to produce a 

 smoked haddock containing a higher percentage of water than is 

 ordinarily found in this product, which has retarded losses in this 

 process; but to date a successful method has not been found for 

 preserving smoked fish for a greater length of time at the usual 

 room temperatures. Studies have been made of the bacterial spoil- 

 age of frozen fish and of fish packed in ice, and considerable progress 

 has been made in developing methods for retarding or overcoming 

 this spoilage which are an improvement over usual practice. 



Preservation of fishery hy products. — Researches in this field have 

 shown where economies can be effected in the manufacture of fish 

 meal to produce a more nutritious product, and have given funda- 

 mental information concerning the effect of manufacturing methods 

 on the factors controlling the nutritive value of the product. 



Studies of the manufacture of fish flour are still in the development 

 stage, being concerned mainly with the study of methods for atomiz- 

 ing macerated fish waste in a heating medium in order to effect 

 extremely rapid drying. 



Research in the chemical and physical constants of haddock-liver 

 oil have shown that while crude haddock-liver oil may be expected 

 to come within the United States Pharmacopoeia limits, the cold 

 pressed oil may be expected to exceed the limit occasionally. The 

 significance of this is confused somewhat by the lower vitamin 

 potency of the oil. This research also has shown that the col- 

 orimetric method for determining vitamin A offers oil manufacturers 

 a rapid and inexpensive estimation of the quality of the various lots 

 of oil prepared. 



Net 'preservation. — For several years this Bureau has been endeav- 

 oring to reduce depreciation and consequent cost of maintaining fish 

 nets by developing net preservatives and encouraging improved 

 handling of the nets. In 1932 the efficacy of covering dyed heavy 

 Avebbing with a specification tar as previously recommended was con- 

 firmed. Chemicals also have been found which retard weed growth 

 on fishing nets, and others which are efficacious antioxidants. Tests 

 also confirmed previous recommendation of the Bureau for cleaning 

 the net and drying in the shade to reduce deterioration. In this con- 

 nection it has been found that washing nets with lime water appears 

 to treble their life. Some preservative principles developed in this 

 research may have application to the preservation of other textile 

 materials, such as sails, awnings, and rope. 



BIOLOGICAL FISHERY INVESTIGATIONS 



All of the most essential major projects of research comprising 

 the investigative program of the Division of Scientific Inquiry, de- 

 veloped through many years of careful planning and organization, 

 have been continued during the past year with only moderate curtail- 

 ment because of reduced appropriations. 



Investigations of the commercial fisheries are concerned witli the 

 changes in abundance of the food fishes of the North and Middle 

 Atlantic areas and with the correction of abuses in the commercial 



