XXIV REPORT TO THE SECRETARY OF COMMERCE 



life of a net is less if it is exposed continuously than if it is immersed 

 in the water intermittently for the same number of hours. In prac- 

 tice this means that frequent lifting, washing;, and drying of nets is a 

 very important procedure and nearly as valuable as the preservative 

 treatment itself. 



By- products. — The reduction of fish into oil and scrap or meal is a 

 large industry of long standing, yet it still presents mam' formidable 

 problems. In the case of the menhaden industry', the irregular sup- 

 ply is responsible for an excessive overhead cost. This year the tech- 

 nologists have striven to decrease labor costs by showing that appro- 

 priate machinery can be installed and by advocating the use of a 

 simple cost system to detect unsuspected expensive operations. The 

 relation between care in operation of existing equipment and the 

 quality of the resulting od has been emphasized. These points were 

 stressed because they promised immediate profits to owners. 



The salvage of small quantities of market waste and unmarketable 

 or rough fish or of waste produced on shipboard is another problem 

 to which attention was given. However, investigation indicates that 

 existing machinery for this purpose is too expensive to be i)ractical. 

 and at present the only method of salvage is to make " acid scrap." 

 Larger and more constant supjilies, such as those originating from 

 filleting plants, justify the use of a vacuum dryer, and a number have 

 been installed. Ex]3eriments have been conducted upon vacuum dry- 

 ing and the best conditions for the process found. However, the 

 design of commercial sized plants does not seem altogether satisfac- 

 tory from the standpoint of economy of time and power and hence 

 exhaustive studies of cost will be made. Another difficult problem is 

 that resulting from the rapid accumulation of salmon waste in com- 

 munities so isolated that labor is expensive and transportation costs 

 high. 



The white meal produced by the vacuum process from haddock and 

 cod waste is a most excellent stock feed. It is valued highly al)road 

 (especially in Germany, where it is used extensively for hog feeding) 

 as a protein supplement for cereals, as it also produces a sturdy 

 frame and prevents deficiency diseases because it Isrings with it from 

 the sea elements necessary to normal life. Many elements are not 

 fou.nd in proper proportions in the usual feed of farm animals; iodine,, 

 for instance, may be absent and goiter result, or calcium may be 

 deficient and bone formation (and general health) be faulty as a 

 consequence. There are many publications to show that fish meal 

 prevents such results and the bureau has given them wide circulation 

 and also supplied experimenters Avith material for trial. While 

 American producers exported considerable fish meal in 1927. the 1928- 

 production probably will be absorbed more freely in this country, and 

 already some has been imported. 



Nutritive value of fsh. — The work in this field consisted mainly in 

 " biological analyses " of the proteins of haddock and herring and 

 indicates that these are excellent supplements for cereals, comparing 

 favorably with steak, liver, or kidney. They do not supplement 

 legumes well, however. Other metabolism studies will be made, as 

 feeding experience has shown fish meal to be most effective in 

 jjromoting growth. 



