ECONOMICS OF THE FISHERIES 357 



of supply, the few and poorly equipped laboratories, the non-scientiiically- 

 minded fisheries industry has done little to exploit them. 



By-product Oil and Meal. The leading products of the fisheries other than 

 human food are oil and the dried substance of fish free, or nearly free, of 

 oil. The dry substance of edible grade for animals is fish meal, of lower 

 grade it is scrap used for fertilizer. 



Meal and oil are made as by-products from the residues of fish left 

 from filleting, canning and other preparations. Meal, oil, and scrap are the 

 main products from the menhaden, dogfish, and shark fisheries, and from 

 a large part of the production of certain edible fishes, such as pilchard, 

 herring, and some others caught and processed in their entirety for this 

 purpose, 



a. Fish Oil. It is a singular fact that the oil or fat in fishes is stored in 

 either the body of the fish, or in the liver, but rarely in quantity in both 

 body and liver. In the salmon, herring, menhaden, shad, mackerel, mullet, 

 eel, etc., the bulk of the oil is in the body; in the sharks and codfishes it is 

 contained in very large quantities in the liver (50 per cent or more) and 

 the livers of halibut, tunas, swordfish, and several others, contain 10 per 

 cent to 20 per cent oil. The liver oils are generally rich, and the body oils 

 relatively poor, in vitamins A or D or both. Accordingly, the liver oils used 

 for medicinal purposes command a very much higher price than body oils 

 which are used mostly for industrial purposes. Vitamin A is present in all 

 fish livers that have been examined, but in greatly varying amounts and 

 concentration; vitamin D is much less prevalent, being absent from all 

 sharks and sturgeons (whose bones are not calcified) ; it is found in high 

 concentration only in the swordfish and tunas. Both vitamins seem to be 

 most highly concentrated in big fishes and old individuals, and in species 

 that are high on the chain of life, several stages from the basic vegetation. 

 These are not only more economical to handle because of their large size 

 but yield more vitamins. Much vitamin liver oils go to waste in small fishes 

 because of the expense of collecting the livers. 



By far the greater part of vitamin liver oils come from Pacific Ocean 

 species, both oriental and occidental. The tuna, swordfish and halibut, 

 found in both the Atlantic and Pacific yield oils of about the same quantity 

 and potency, but these fishes seem to be less abundant in the Atlantic. The 

 greatest of all sources of vitamin A are the Pacific sharks (dogfish, soupfin 

 and hammerhead). Their relatives, the Atlantic spiny dogfish and the South 

 Atlantic and Caribbean sharks, yield relatively low potency oils. 



All of the vitamins were originally found in and derived from natural 

 foods; all of the common ones are now manufactured synthetically, except, 

 until recently. A; however, this vitamin may go the way of all the others from 



