can long survive the attacks of a new unnatural enemy armed with the energy, the resources, and the intelligence of civilized man. Fortunately, the qualities which render him the most resistless of enemies also enable him to become a producer as well as a destroyer; and, while the fear of him and the dread of him is upon every beast of the earth and upon every fowl of the air and upon all the fishes of the sea—while they are all delivered into his hands, and are powerless to resist him—he alone of all animals is able to make good the destruction caused by his ravages, and to increase, by agriculture, by domestication, by selection and improvement, and by artificial propagation, the animals and plants which he destroys.
Can these influences be brought to bear upon marine animals? Can human intelligence and skill and power over Nature be so employed as to make quickly, by artificial means, that slight adjustment in the birth-rate of food-fishes which would have been brought about more slowly by natural agencies if man had long occupied his present rank among their enemies?
Looked at in this way, the proposition certainly does not seem to be impracticable; and, while human efforts in this field are of too recent a date to furnish positive evidence, I believe that I have shown that there is no a priori impossibility and no logical basis for a negative answer to the question. The results which have already been reached by the artificial propagation of certain sea fishes, like the shad, which make periodical visits to fresh water, are extremely interesting, as they furnish indirect evidence which is very conclusive. They prove that human influence produces very prompt and decidedly advantageous results in the case of these fishes, and thus give us every reason to hope that equally valuable results will follow—a little more slowly, perhaps—from our efforts to increase the supply of more strictly marine species.
In the year 1880 the fisheries census and special investigations which were carried on under the direction of the United States Fish Commission proved that there had been a most rapid and alarming decline in the value of the shad-fisheries in the rivers and bays and sounds of our Atlantic coast, and that there was every reason to fear that in a few years the shad would be utterly exterminated. The adult shad is an oceanic fish, but each spring it enters one of the inlets or bays and makes its way up to the fresh-water streams to reproduce its kind. The supply of shad for the market is caught during this spring migration, when the fishes enter our inland waters plump and fat after their winter's feast upon the abundant supply of food which they find in the ocean. As they spend the greater part of each year gathering up and converting into the substance of their own bodies the innumerable minute marine organisms which would be of no value whatever to
