Figure 6.- -Index of the total catch of dogfish livers 

 landed by the same boats fishing sink gill nets in the 

 periods 1943-44, 1944-45. and 1945-46 in Hecate 

 Strait. Determined by the method of link relatives. 



area, probably resulted from the intense 

 fishery. Barraclough (1948) has said that 

 the decline in availability of dogfish in Hecate 

 Strait was closely related to removal of the 

 older age classes from the population, Barra- 

 clough summarized his findings by pointing 

 out that "the decline in availability and vitamin 

 A potency of dogfish was not sufficient evi- 

 dence to indicate biological depletion; however, 

 the economic consideration of reduced yield 

 per boat accompanied by reduced value per 

 unit was a matter of real concern," The 

 Canadian studies were on a rather small 

 scale and lack the confirmation of support- 

 ing statistical data, and the conclusions or 

 trends indicated in the Hecate Strait fishery 

 are not necessarily indicative of the overall 

 coastal fishery, 



Shepard and Stevenson (1956) give an indi- 

 cation of the size of dogfish stocks and possible 

 effects of the fishery off British Columbia, 

 Using reduction of stock of about 50 percent 

 (from Barraclough's 1948 work)for the 1940's, 

 and neglecting natural mortality and recruit- 

 ment, they estimate that the 500 million 

 pounds of dogfish removed in approximately 

 5 years represents about one-half the original 

 stock. If recruitment and natural mortality 

 were approximately equivalent, then a fishing 

 mortality in the vicinity of 13 percent per 

 year could be considered sufficient to mate- 

 rially reduce the dogfish. 



What happened to the populations after fish- 

 ing ceased is purely speculative. The life 

 history of the dogfish is not conducive to a 

 rapid buildup of the stocks to their former 

 abundance. Contemporary estimates as to 

 the status of the stocks after the fishery, 

 as compared with their status prior to the 

 fishery, are subjective. Reports from fisher- 

 men suggest that dogfish have become 

 increasingly abundant in recent years,Whether 

 they are as numerous as during the period 

 prior to the fishery is an academic question. 

 That dogfish are again very abundant seems 

 evident from reports of fishermen, biologists, 

 and sportsmen. Shepard and Stevenson (1956) 

 report that: "In consequence of the cessation 

 of fishing for dogfish, the stock now appears 

 to be in the process of a strong recovery. 

 Already the dogfish has become a plague 

 on many of the British Columbia fishing 

 grounds — disrupting trawling and seine fish- 

 eries for other species." 



EFFECTS OF LARGE DOGFISH 

 POPULATIONS ON MAN 



The presence of increasing numbers of 

 dogfish in offshore waters and within Paget 

 Sound has stimulated industry requests for 

 assistance. Destruction of gear, excess wear 

 on fishing nets, loss of fishing time, practical 

 loss of fishing areas, and reduction in food 

 and shellfish stocks through predation are 

 attributed to dogfish. 



Gear losses and damage are most common 

 in the net fisheries (trawl, seine, and gill 

 net) and often result when nets are set or 

 dragged in areas heavily infested by dogfish. 

 If the catch of dogfish is large enough, the 

 entire net may be lost. Because of the rela- 

 tively high specific gravity of dogfish, when 

 extremely large catches are made, the weight 

 may be sufficient to break the entire net or 

 portions of it. Net damage is probably most 

 prevalent in the trawl fisheries, although it 

 also has been reported in the salmon seine 

 and gill net fisheries. 



Gear losses are also experienced in com- 

 mercial and sport line fisheries, where the 



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