Page:Popular Science Monthly Volume 35.djvu/382

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the species and to keep the area which it inhabits stocked with as many adults as it can support.

All the natural sources of mortality are thus provided for. As each species is slowly and gradually brought into harmonious adjustment to the conditions of its environment, its birth-rate, like all its other attributes, is regulated and adapted to meet all the natural demands upon it. Now what happens if, after each one of the natural enemies has claimed its victims, a new enemy not provided for by Nature suddenly attacks the few adult survivors which Nature has provided to perpetuate the species? What happens when the last drop falls into the brimming bucket? What happens when the proverbial last straw is put on the load? It may be quite true that, for each codfish which man catches, the natural enemies destroy a million. That has no bearing on the subject. Nature has provided for the destruction of the million. Before their birth they were destined to premature death. The one was reserved by Nature for another purpose.

If the destructive influence of man had been gradually brought to bear, and had kept pace with the evolution of the species, natural selection would have provided a remedy, and the birth-rate would have been correspondingly increased; but this has not been the case; and, while man might not be able to make any impression on the broad base of the pyramid, we must remember that he does not attack the base, but the pointed apex. The fact that sea-fishes are so enormously prolific is entirely irrelevant. Their high birth-rate is an adjustment to their natural environment, while the influence of man is a new factor which has not been provided against.

It is difficult to get statistical information regarding marine animals, but there is ample evidence that they may be exterminated by man. The Bahama sponge-fishermen complain that they are now compelled to make long voyages and to visit remote banks for sponges which in former years could be gathered in abundance near the seaports. It is well known that, just before the oil from the wells of Pennsylvania came into common use, the sperm whales had become so scarce that they were in imminent danger of extermination. The scarcity and the high price of sea-fishes in the vicinity of large seaport towns are unquestionable; and the shore-fisheries of the New England coast, to which Cape Cod owes its name, have been so completely destroyed that, when the Cape Cod fishermen caught, a few months ago, in their nets some of the young codfishes which had been hatched in the Fish Commission laboratory at Wood's Holl, they brought them to the naturalists as specimens of a new and unknown species. The destruction of sea-fishes may require many years, but there is no animal on earth large enough to be valuable as human food which