EFFECTS OF THE MENHADEN AND MACKEREL FISHERIES. 291 
mind that its absence from our waters would probably reduce all our other sea 
fisheries to at least one-fourth their present extent. If his premises are sound, 
the estimate is probably approximately correct, otherwise it is subject to criti- 
cism. In the Gulf of St. Lawrence, where, for a portion of the year at least, the 
principal food of the cod is capelin and herring, the absence of these foods is 
concomitant with the absence of cod. 
In the second report of the Commissioner of Fisheries of the United States, 
Baird ascribes the decadence of the inshore cod fishery of New England to the 
enormous diminution in the number of alewives; ‘‘at least,’’ he says, ‘‘the 
coincidence is remarkable.’’ If the same relation is known to exist between 
the cod and the alewives on the New England coast as between the cod and 
herring or capelin in the Gulf of St. Lawrence, then such a conclusion is well 
founded. But as it is not shown to be a fact, it can be considered only a con- 
jecture. Surmises based on coincidences will not solve problems. Therefore, 
in order to determine even with any degree of approximation the effects of 
the reduction in numbers of any species in our waters upon other species to 
any extent feeding upon them, the habits of not only these forms but others 
as well must be very thoroughly known in all their intricate interrelations. 
The list of fishes enumerated by Goode as destructive enemies of men- 
haden does not comprise all the species that at times eat menhaden, and it 
includes some that are not known to feed upon them at all. The assumption 
that they do is made partly from the fact that they are built on the model of 
predaceous fishes, and partly because they are sometimes caught on menhaden 
bait. The first part is to some extent justified, since it is safe to assume that 
a species which to any extent eats other fishes will eat menhaden if it can get 
them; but it is not safe to infer that it consumes enormous quantities, as its 
habits may be such that it is not brought in contact with such numbers, or food 
which it prefers may be at the same time present. That a fish is caught on 
certain kinds of bait or that the bait is the most successful to use does not 
signify that the principal food of the fish is the species used as bait. Not 
infrequently the best bait for some fishes is something that does not coinhabit 
those waters. 
To what extent any species subsists upon menhaden and the number of 
species that feeds to some extent upon them is not known. ‘Therefore no 
reliable deductions can be made regarding the effect upon such fishes were 
they deprived of the supply of menhaden. However, every menhaden caught 
reduces the number of those fish by one; every thousand or million reduces the 
number by a thousand or a million. Therefore the menhaden fisheries must, 
theoretically at least, have their effect upon the species that feed upon the men- 
haden by depriving them of so much food. They also have effect upon the 
menhaden sought by rendering those that escape capture more liable to be eaten 
by predaceous enemies. 
