BY-PRODUCTS OF FISHERY INDUSTRIES 217 



Menhaden scrap is sold chiefly to fertiHzer manu- 

 facturers, who mix it with potassium salts and acid 

 phosphate. In recent years much scrap has been sold 

 to stock feeders as meal for hogs and cattle. It also 

 is a popular chicken feed. 



In California the surplus pilchards or sardines 

 are cooked and rendered into oil and scrap by a 

 process similar to the one described above. Much 

 sardine scrap is also made by an extraction process 

 in which the fish are cooked and dried by direct heat 

 in a continuous cooker. The cooked, dried scrap, 

 which is known as unfinished meal, is extracted \fvdth 

 gasoline or low-boiling naphtha. After dissolving out 

 practically all of the oil, the naphtha is separated 

 from the meal and distilled. Thus the naphtha is 

 recovered, and the fish-oil is left in the still. The 

 extracted scrap is heated with steam until all of the 

 gasoline is driven oif . This scrap is much lower in oil 

 content than pressed scrap and for this reason is pre- 

 ferred for chicken feed, nearly the entire production 

 being sold for this purpose. 



In Washington and some places in Alaska, the 

 inedible parts of salmon are manufactured into scrap 

 and oil by cooking and pressing. Large quantities of 

 Alaskan herring are also converted into meal and oil. 

 The part played by fish-oil in American industries 

 has already been discussed, but no mention of its 

 valuable properties has been made. Menhaden, sal- 

 mon, herring, and sardine oil which have been freed 

 from stearin are very valuable succedanea for linseed 

 and china-wood oils for use in the preparations of 

 paints and varnishes. Old linseed-oil films become 



