112 U. S. BUREAU OF FISHERIES 



The information secured concerning the types of gear used (the 

 entire analysis has been confined to the records of gill net fishermen 

 and the fish wheel records mentioned above) indicates that during 

 the first six or eight years covered by our data, 1909 to about 1916, 

 there was a steady improvement in the efficiency of the nets. Also 

 it was during the same period that the sail boats became obsolete 

 and boats powered with gasoline engines came into practically 

 universal use in tliis fishery. 



These two factors undoubtedly increased the catch per unit of 

 efl^ort and gear during that time when the change was taking place 

 and must be seriously considered in interpreting the final curves of 

 relative abundance. 



The additional data collected during 1930 confirms the conclusions 

 drawn from the previously gathered records: That from 1909 to 1925, 

 the trend of catch per unit of effort and gear was approximately 

 constant and that from 1925 to 1930 it has dropped at an alarming 



TECHNOLOGICAL INVESTIGATIONS 



Fisheries technology covers a very wide field of activity, in that it 

 deals with an important food industry and sources of valued products 

 in the arts and industries. The study of the technology of many food 

 industries is an extensive subject and few, if any, food industries are 

 as highly diversified as the fishery industries. Fisheries technology 

 is at present demanding the attention and best efforts of chemists, 

 engineers, and bacteriologists. Until a few years ago little had been 

 accomplished in this field of food technology. Much remains yet to 

 be accomplished. The Bureau of Fisheries, the College of Fisheries 

 of the University of Washington, Seattle, Wash., and some of the 

 larger fishery companies have been the leaders in this field. Develop- 

 ments have come very rapidly in recent years. The technical hand- 

 ling, preservation, and distribution of foods through the medium of 

 refrigeration, particularly to inland consumers, has been largely a 

 result of research activities in fisheries technology. Great progress 

 has been made in the elimination of waste in the fishery industries. 

 The enormous strides in the manufacture and uses of marine by- 

 products are a real contribution to the science of animal nutrition. 

 In fact, progress in some branches of fisheries technology, described 

 in detail in the following pages, has been so great that other food 

 industries are looking to this industry for guidance. 



BY-PRODUCTS AND PRODUCTION METHODS 

 THE MENHADEN INDUSTRY 



For years fish scrap and fish oil have been established by-products 

 of the fishing industry. Until recently, however, they were looked 

 upon as low-grade materials. Fish scrap was manufactured and sold 

 for use in fertilizer compounds and fish oil was marketed solely as a 

 cheap substitute for other oils used by several technical industries. 

 Within the past few years, largely through the efforts of the Bureau 

 of Fisheries and certain enterprising individ^ials associated with the 

 fish scrap and fish oil industry these products have become recognized 

 as possessing greater potential usefulness. Investigation has shown 



