season that dogfish are on the coast in large numbers, but it lias 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 $±00,000. 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 i 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. 
