The fisheries application of sonar

Sonar has proved invaluable in pelagic fisheries as a direct detector of fish. In demersal fisheries the value of sonar except in Arctic cod fisheries is still mainly indirect¿its chief value is for navigation and determination of the type of sea bed. Real advance seems to depend on methods which will improve definition and interpretability really substantially¿to the stage of giving some sort of recognizable picture of the undersea scene.