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Cod can travel up to several thousand kilometres when they migrate, and in the Barents sea off the coast of Norway, there are two distinct types of migration; the feeding migration and the spawning migration. Using underwater microphones called hydrophones, scientists have discovered that far from being silent, cod are vocal fish.
Three different sounds have been identified; the first is a simple grunt. What’s particularly interesting about the sound, is that the size of the fish can be estimated from the sound they produce. Large fish produce lower frequency (deeper sounding and generally louder grunts) than smaller fish. When the fish become more aggressive or territorial then the grunt production increases, ie rapid grunting, and when the cod are spawning then they produce a low rumbling sound.
Jana Winderen is a sound recordist who is fascinated to learn that cod produce sounds was keen to try and record them. Jana was also joined by sound recordist Chris Watson to try and record the sounds of cod on their spawning grounds at Lindåspollen in Norway.
You can hear about Jana’s attempt to record cod on migration in the Barents sea off the coast of Norway in World On the Move on Tuesday 4th March 2008, and you can read her audio diary here.