372 U. S. BUREAU OF FISHERIES 



the many experiments conducted by numerous investigators, have 

 been omitted, for to burden the reader with such a mass of material 

 would defeat the })urpose of this publication. 



This report is intended not only for the scientist or biochemist, 

 but also for the animal feeder and for those engaged in the produc- 

 tion of fish meals and shellfish meals. 



Marine products are an extremely important potential source of 

 numerous nutritional requirements in the dietary of man and his 

 domestic animals. These products of the sea are valuable for their 

 vitamin potency, protein content of a high cofRcient of digestibility, 

 and for their quantity and variety of mineral constituents. The 

 diversification of mineral content may be realized and emphasized 

 by calling attention to the fact that scientists have found in sea water 

 at least 34 elements useful to life. Much research remains to be 

 done to determine the role played by minerals in nutrition; in fact, 

 this field of nutrition has hardly begun to be investigated. How- 

 ever, outstanding examples of the importance of obtaining knowledge 

 along these lines are the demonstration of the role played by copper 

 and iron in one type of mitritional anemia, and iodine in the pre- 

 vention and cure of simple goiter. Marine products offer the richest 

 known sources of materials for these mineral studies in the science 

 of nutrition. • This should a])peal especially to scientific investiga- 

 tors. It can not be too emphatically stated to w^orkers in the science 

 of nutrition that here lies a pioneer field of potential investigation 

 offering rich rewards and a veritable " gold mine " of possibilities 

 in scientific accomplishment. 



Fish meals and shellfisli meals are manufactured as by-products 

 from the waste or inedible parts of fish and shellfish accumulating 

 in large quantities at various concentration points of our fishery 

 industries. Some fish meals, such as the menhaden, are produced 

 from wdiole nonedible fish. If the fish or fish waste contains much 

 oil, it is both cooked and pressed and the remaining so-called 

 " green " scrap is dried and ground. In certain localities in Maine 

 the oily herring scrap is dried directly without cooking or pressing. 

 If the waste is low in oil, as is the case with the waste accruing in 

 some of the North Atlantic fisheries, it is either directly dried and 

 ground, or cooked, pressed, dried, and ground. Processes of drying 

 vary considerably in different plants. In general, the meal may 

 have been dried either by solar evaporation, hot air or hot furnace 

 gases, or by steam heat wath or without reduced pressure. The Bu- 

 reau of Fisheries is very much interested at present in investigatiouh 

 of the relative nutritive value of fisli meals produced by various 

 methods of drying. Scientific data, so far available, seem to indi- 

 cate that there is a wider variance in the nutritive value of the same 

 sources of material prepared according to different processes of dry- 

 ing than there is in the nutritive qualities of meals prepared from 

 different species of fish by the same type of dryer. 



Fish meals may be divided into two general classes according to 

 their oil content; namely, oily fish meals and nonoily fish meals. 

 Oily fish meals may be considered as those prepared from fish in 

 which the oils are distributed generally throughout their bodies, 

 whereas nonoily fish meals come from fish whose oils are concen- 

 trated mainly in their livers. A certain amount of prejudice has 



