Fisheries Acoustics

Abstract

How many fish are in the sea? This question has always been important, but today has added relevance as we realize how fishing has devastated ocean resources. Most standard methods of counting fish end up killing them with nets, traps or hooks. Photography or visual counts can be used, but the clear waters necessary are rare. Examining the characteristics of reflected sound waves in an analogous way to radar is a smart alternative because it is non-lethal, works in turbid waters, covers vast areas and can be very cost-effective compared to catching the fish. To use the words of Douglas Adams (1979), analysing echoes is ‘mostly harmless’, and so ways of encouraging its use should be supported.