were found in the stomach of a grey seal {Hali- 

 choerus grypus) but constituted only 1 percent of 

 the volume of the stomach contents. Killer 

 whales {Grampus orca) may feed on dogfish, but 

 probably only when other food is unavailable. 

 One killer whale was seen, "Scavenging round 

 longlining vessel, eating dogfish." in the Strait of 

 Belle Isle, July 1953 (Sergeant and Fisher, 1957). 

 No doubt the relatively large size, spines, and 

 tough, scabrous skin of the dogfish are effective 

 deterrents to predation. 



UTILIZATION OF THE SPINY DOGFISH 



The dogfish is not completely valueless or use- 

 less. It has some slight value, in limited quantity, 

 in the United States, and it has greater value in 

 some parts of the world where it is sought as a food 

 fish. The greatest value of the dogfish in North 

 American waters is as an industrial fish for proc- 

 essing into oil and meal, and at one time it was 

 under intense exploitation for its liver as a source 

 of natural vitamin A (fig. 8). 



The Bureau of Commerical Fisheries collects 

 and publishes yearly summaries 3 of U.S. fisheries 

 by regions. In this paper, data collected from the 

 Puget Sound, Middle Atlantic, and New England 

 regions are discussed. The data given in table 10, 

 and shown in figures 8 and 9, are taken from vari- 

 ous sections of the statistical reports. 



Table 10. — Catch of grayfish ' at principal regions, 

 1915-61— Continued 



See footnotes at end of table. 



i Grayfish is the market name for dogfish. . 



2 No survey on east coast. Data reported were those collected in 1940. 



' Fishery statistics of the United States. 1919-63, U.S. Depart- 

 ment of the Interior, Fish and Wildlife Service, and predecessor 

 agencies. 



Figure 8. — Dogfish catch from Puget Sound, Wash., 

 1915-61. 



LIFE HISTORY OF SPINY DOGFISH 



545 



