The fisherman’s harvest differs from that of the farmer in one important respect. Fishes grow for three or four, or more, years before they are mature. Now, only mature fish as a rule have any considerable commercial value, and only mature fish are able to reproduce their kind and so maintain the existence of the fishery. On the fishing grounds, both mature and immature fish are mingled together, and in capturing the one it is practically impossible to avoid netting the other. To some extent the capture of immature fish is avoided by making the mesh of the net of such a size that the smaller fish can escape. With drift nets only mature fish are caught, the small ones escaping; but with trawl nets it is otherwise. The trawl net is essentially a large string bag that is drawn open-mouthed along the sea bottom, scooping up wholesale all bottom-living fish, such as cod, haddock, sole and plaice. All go into the net, both large and small, and, although the young fish ultimately escape through the meshes, many of them are damaged in so doing, while many young, flat fish, lying on the sea bottom, are damaged by the foot rope of the net, as it passes over them. Certain fishing grounds, such as the Dogger Bank, were almost depopulated of flat fish in the years just previous to the war. Fortunately for the future of the fisheries, the trawl, can only be worked on smooth ground, and at depths not exceeding two hundred and fifty fathoms, so that only a small percentage of the actual fishing grounds is affected by it. Also, when a fishing ground shows signs of becoming exhausted by over-fishing, it is less frequented by fishermen, owing to the reduced catches that can be obtained, and thus it tends automatically to recover. Nevertheless, it is desirable that fishing should be so organized and restrained, that the fertility of the fishing grounds is not imperilled. In the distant future it may become possible to re-stock partially exhausted grounds with young fish, artificially reared in a hatchery. Oceanography—the study of the ocean and its inhabitants—is one of the youngest of sciences. Yet, to an island people such as we are, it should be one of the most important, for it is only by the study of oceanography that we can hope to found a systematic, organized aquiculture. The beginning of a simple aquiculture is to be seen in the cultivation of shellfish, such as oysters and mussels, by the inshore fishermen. Of recent years, experiments have been carried out by the Fishery Boards of England, Scotland, Germany, and the United States of America, with the object of increasing the productivity of certain fishing grounds by adding large numbers of artificially hatched, young fish. For some years the Fishery Board for Scotland added annually about twenty million plaice larvae to certain confined sea areas (Upper Loch Fyne), and found, as a result, that the number of young plaice on the shallow beaches was doubled.