SUMMARY 



The spiny dogfish, Squalus acanthias, which 

 ranges through the temperate and subarctic 

 waters of both the North Atlantic and North 

 Pacific Oceans, has increased in numbers 

 until fishermen have become concerned about 

 its depredations. 



Dogfish abundance centers in the eastern 

 Pacific include Puget Sound, Strait of Georgia, 

 and the Continental Shelf from central Wash- 

 ington to Hecate Strait, B. C. — all areas of 

 intensive commercial and sport fishing ac- 

 tivity. Offshore dogfish populations appear to 

 be highly mobile, whereas those of inshore 

 areas seem to be relatively stable. 



A mature female dogfish may give birth to 

 from 2 to 20 pups every second year; dogfish 

 longevity may exceed 30 years. Most studies 

 indicate that dogfish are opportunists rather 

 than discriminant feeders. Ratfish, krill, 

 shrimp, herring, flatfish, eulachon, and octopus 

 have been noted in stomachs of dogfish caught. 

 There is no evidence that dogfish affect salmon 

 stocks adversely through predation. 



Small fisheries for dogfish have been carried 

 out along the coast of the Pacific Northwest 

 since Indian days. Both the Indians and early 

 white settlers used dogfish oil for a variety 

 of lighting and lubricating functions. Spasmodic 

 attempts have been made more recently to use 

 the dogfish as human food, but all such at- 

 tempts in this country have been relatively 

 unsuccessful. In Europe the dogfish is used 

 to some extent as food — generally as fried 

 fish. 



During World War II, a sizable fishery for 

 the Pacific dogfish was brought about by the 

 demand for a source of vitamin A and the 

 development of methods of extracting the 

 vitamin from relatively low potency oils. 

 With the advent of synthetic vitamins, how- 

 ever, the fishery collapsed, not to be renewed. 



With the collapse of the fishery, the dogfish 

 populations, which Canadian studies Indicated 

 were considerably reduced as a result of fish- 

 ing efforts, began to increase — leading to the 

 present high stock levels and interference 



with more valuable fishing endeavors. Prac- 

 tically all segments of commercial and sport 

 fisheries claim losses from dogfish. Esti- 

 mates by industry members indicate that the 

 annual loss in gear damage alone exceeds 

 $2 million. 



Three general methods for controlling dog- 

 fish seem to be available: (1) selective poison- 

 ing, (2) use of deterrents and repellents, and 

 (3) reduction of dogfish numbers through fish- 

 ing efforts. Selective poisoning, although theo- 

 retically possible, would be difficult to control 

 in practice. There are, at present, no 

 deterrents or repellents that are effective 

 under all conditions, and application of such 

 substances to commercial gear, even if fully 

 effective, would be extremely expensive. Per- 

 haps, in the future, the selective action of a 

 series of electrodes could be used. 



The best possibility for controlling dog- 

 fish, however, appears to be through fishing 

 effort. This could be achieved through (1) pay- 

 ment to the fishermen of a bounty, (2) initia- 

 tion of a vessel charter system, or (3) de- 

 velopment of high-priced markets for dogfish 

 products, leading to development of a com- 

 mercial dogfish fishery. The first two schemes 

 would require continual Government support; 

 the third scheme would require support only 

 during the developmental stages, after which 

 it could be expected to be self-sustaining. 



Possibilities for dogfish markets exist in 

 development of uses for both oils and protein. 

 Unique uses, if they could be developed, would 

 be more effective in stimulating and support- 

 ing a fishery than would uses that could be 

 filled by products from other sources. Dog- 

 fish liver oil, containing approximately 15 

 percent unsaponifiables including glycerol 

 ethers, appears to hold promise for develop- 

 ment of unique uses. Nonunique uses for prod- 

 ucts from the body oil and the carcass (protein) 

 could then be used to distribute production 

 costs over the entire animal. 



If a domestic dogfish fishery is to be self- 

 sustaining, some adjustments in import duties 

 on dogfish products and other fish oils from 

 abroad would probably have to be made, or at 

 least the import situation would have to be 

 examined carefully. 



20 



