carcass utilization. Otherwise, oil users would 

 probably find it cheaper to import the oil from 

 Japan or other foreign countries. 



The most profitable use for the carcasses 

 would undoubtedly be as food for humans, but 

 development of this would be difficult. Prin- 

 cipal objections to such development are: 

 (1) in most parts of the country there is a 

 strong subjective prejudice against eating 

 shark, (2) sharks contain urea, which would 

 have to be removed or fixed in the tissues 

 by special processing methods before the flesh 

 would be acceptable to most people and before 

 canning could be accomplished, and (3) com- 

 pared with many other low-priced and under- 

 utilized species of fishes, the palatability of 

 dogfish is low. These are the same difficulties 

 that have faced previous attempts to market 

 dogfish in the United States and in Europe. 



Use of dogfish as canned petfood is open to 

 some of the same objections, and many canners 

 also object to sharks because their tough hides 

 jam the fish grinders at petfood plants. Installa- 

 tion of grinders of different design would over- 

 come the latter objection, but as long as there 

 is a steady supply of the many low-cost and 

 otherwise underutilized fishes currently being 

 used in petfoods, development of a petfood 

 market for dogfish seems unlikely. 



A third possibility is that of using dogfish 

 carcasses for fish meal. This possibility seems 

 the best of the three discussed, and some 

 carcasses are being used for meals already. 

 But here, too, there are objections and prob- 

 lems to be met. The meal from dogfish has a 

 relatively low nutritional value. Also, it con- 

 tains urea, which interferes with traditional 

 tests for protein content; and often the urea 

 nitrogen is not subtracted from the protein 

 nitrogen, leading the user to believe that 

 he is feeding a product superior in protein 

 content to what is actually the case. Research 

 to raise the quality of dogfish meal is badly 

 needed. In addition, tests are needed to deter- 

 mine the suitability of dogfish meals in foods 

 for animals other than poultry (for which most 

 of the meal now being produced is used). Such 

 research could open new and extensive 

 markets. Research already conducted, for 

 instance, has demonstrated that cattle have 



the ability to use urea nitrogen, whereas this 

 ability is lacking in poultry. 



In summary a list has been compiled of 

 the most urgent research needs if uses are 

 to be developed for dogfish products. Among 

 the principal needs are: 



1. General research on metabolism of 

 urea in dogfish and location of the urea in the 

 fish. If more were known about this, it might 

 be possible to eliminate the urea before 

 processing the carcasses. 



2. Research on the chemical makeup of 

 dogfish oils. This research would include 

 studies of both fatty acid composition of dog- 

 fish body and dogfish liver oils, and, espe- 

 cially as a main item of research, the com- 

 position of the unsaponifiable matter in dogfish 

 liver oil. 



3. Research on utilization of dogfish oil 

 for specific purposes. A project should be 

 started first at Hormel Institute on utilization 

 of glyceryl ethers as an antioxidant vehicle. 

 Later, as results on composition of dogfish 

 oils become known, other potential uses indi- 

 cated by these results should be looked into. 



4. Investigation of the quality for chick 

 feed of currently produced dogfish meal. 



5. Study of the possibility of using dog- 

 fish meal for cattle feed. 



6. Development of the improvements in 

 processing dogfish meal to give better quality 

 meal for poultry or cattle feed. 



Unless sufficient funds are available for con- 

 current technological work on several of these 

 aspects, it probably would not be worthwhile 

 to undertake any of them. Solving of just one 

 aspect of the problem would lead nowhere. 

 As shown above, the various difficulties to 

 utilization of dogfish are interrelated; and 

 unless a balanced approach considering all 

 aspects can be made, little chance of solving 

 the problem exists. 



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