The importance of sound to the Atlantic cod, Gadus morhua, and the Atlantic haddock, Melanogrammus aeglefinus.

The gadoid fishes, including the Atlantic cod and haddock, are currently being exploited close to their safe biological limits, requiring restrictions upon the human activities that may harm them. This has prompted interest in the biology of such fishes. Studies of the cod and haddock have shown highly complex behavior, involving prolonged and energetic visual and acoustic displays. Different sounds are produced in different behavioral contexts and are emitted almost continuously by cod and haddock, especially throughout the spawning season (February to May). The distinctive characteristics of these sounds make it possible to locate spawning cod and haddock at their marine spawning grounds. Human activities in these areas may affect their spawning adversely and have deleterious effects upon their stocks. Man-made sounds in water do have an adverse effect upon cod and haddock, and other fishes. Listening for the cod and haddock sounds provides a reliable, non-invasive technique for detecting their locations, and especially their spawning areas, and enables them to be protected well.