FISHERY INDUSTRIES OF THE UNITED STATES, 1930 113 



that properly prepared ground-fish meal is a valuable animal feedstuff 

 and carefully rendered oils have increased value for technical use and 

 that certain of them possess sufficient vitamin A and D potency to 

 warrant their use in animal feeding. 



Fishery by-products of the type manufactured in the past are de- 

 creasing in usefulness as competitive industries have progressed. 

 Fishery by-products of improved quality have at least kept pace 



Figure 1. — Laboratory press used in connection with studies in men- 

 haden industry 



with competitive products and in some cases have gained increased 

 prestige and even greater value. 



During the past year the bureau's technologists completed an 

 extended study of tke menhaden industry, a summary of the findings 

 follows : 



(1) The bilge water from a menhaden steamer generally contains 

 sufficient oil to warrant recovery at the factory. 



(2) Most efficient operation from a continuous screw press may be 

 expected when (a) the liquors are not required to traverse a great 

 thickness of press cake, (b) the pressure is increased slowly, and (c) 



