Changes in the Sea

Abstract

In contrast to land and fresh waters the sea seems still almost inviolate. Yet big changes in the distribution of species have already begun as a result of human actions during the last hundred years. These actions are of three kinds. First the digging of new canals. Secondly, accidental transport on ships. And thirdly, deliberate introductions. The Panama Canal, though it has in a formal sense split the Nearctic from the Neotropical Region once more, is hardly a serious gap, nor much of a transport line for marine life from one ocean to the other. In 1935 and 1937 Hildebrand made a survey of the animal life in the locks and inner channels of the Canal and found that a good many fishes and some other animals have moved part of the way into the system from each end.¹⁷⁹ Indeed there is no physical obstacle to prevent them from doing so, and he prints a photograph of men picking up a number of very large fish after the emptying of one of the locks. The real barrier is the forty miles of fresh water, especially the great Gatun Lake. The fish that have penetrated at all are, as one would expect, those that can live in brackish and even in fresh water—various gobies and also other kinds of tropical fish. The only species known to have made a complete crossing is the tarpon, Tarpon atlanticus, of which four were found in the lowest lock on the Pacific side when it was emptied in 1937. They have also been reported at the Pacific sea-level terminus, but had not (in 1939) been caught at sea in Panama Bay. They seem to be quite frequent in Gatun Lake.

For though I scorn Oceanus’s lore, Much pain have I for more than loss of realms: The days of peace and slumberous calm are fled;

That was before we knew the winged thing, Victory, might be lost, or might be won.

Keats, Hyperion