﻿18 BULLETIN" 2, U. S. DEPARTMENT OF AGRICULTURE. 



season that dogfish are on the coast in large numbers, but it has been found 

 impossible to make them pay with the price that has been paid for the raw 

 material, $4 per ton. The works were established at Clarks Harbor, Nova 

 Scotia ; Canso, Nova Scotia ; and Shippigan, New Brunswick. Owing to the 

 manner in which fishing is carried on in the vicinity of Shippigan it was not 

 found possible to get any large quantities of dogfish there, and the works at that 

 place have consequently been closed. Last year at Canso over 1,000 tons of 

 dogfish were treated, which yielded about 125 tons of scrap and about 13,500 

 gallons of oil. At Clarks Harbor 360 tons of raw material were handled, 

 which yielded 48 tons of scrap and over 2,600 gallons of oil. The amount of 

 raw material collected at both these works varies from year to year, depending 

 on the plentitude of dogfish. At Canso the average quantity used yearly would 

 be 1,000 tons, and at Clarks Harbor slightly less. 



There is no doubt, however, that such works could be made to pay if located 

 at places where fish offal is also available in considerable quantities and the 

 dogfish were procured at a smaller price. 



It has been stated by Field 1 that the two dogfishes, the smooth 

 and the horned, are tremendously destructive of lobsters and of such 

 food fish as the mackerel and herring. The Massachusetts State 

 Board of Fish Commissioners have estimated that the annual less 

 from the destruction by dogfish of food fish and fishing gear in the 

 State of Massachusetts alone amounts to $400,000. A proportionate 

 loss from their depredations probably obtains for the other States 

 bordering the Atlantic, and a proportionate benefit would accrue 

 from their destruction. 



The method of reproduction of dogfish is quite different from that 

 of fish of the herring family, in that fertilization of the eggs of the 

 dogfish is internal and the young fish are brought forth in a fully 

 developed condition. Each female produces from 4 to 12 young at 

 a time. The eggs of a single menhaden, if permitted to hatch, would 

 produce many thousand young fish. When the enormous rate of 

 their increase is considered, it is readily seen how the menhaden are 

 able to persist in spite of the destruction of such vast numbers of 

 them by their various enemies. The dogfish, on the other hand, ap- 

 parently has but few enemies powerful enough to effect his depletion. 

 Undoubtedly their destruction by natural causes is comparatively 

 slight, so that their comparatively low rate of reproduction is suffi- 

 cient for the maintenance of their numbers. Their low rate of repro- 

 duction makes them particularly vulnerable to the attack of their arti- 

 ficial enemies. Their depletion by a concerted and organized attack 

 of the fishermen therefore should be possible. Before such an 

 attack can be expected, however, a ready market must be provided 

 for the dogfish caught by hook or seine. 



From the foregoing it appears reasonable to believe that dogfish 

 may prove an abundant source of material for the preparation of 



1 Field, Sea Mussels and Dogfish as Food. Fourth International Fish Congress. Bull. 

 Bureau of Fisheries, vol, 28, Pt. I, 243 (1908) ; cf. p. 247. 



