Consistency in the behaviour types of the Atlantic cod: repeatability, timing of migration and geo-location

We investigated the behaviour patterns of coastal (relatively stationary in shallow waters) and migratory frontal (offshore) types of Atlantic cod Gadus morhua in Icelandic waters using information from data storage tags (DSTs). Consistent and repeated patterns of migration were observed for both coastal and frontal cod, with characteristic DST profiles repeated from year to year. The migration timing in 2 successive years was close to being synchronous, suggesting that the onset of migration was consistent from year to year. A tidal location model suggested that the feeding migrations of cod in Icelandic waters were undertaken in groups or shoals during the whole year. The overall stability of the behaviour patterns of both types suggests that coastal and frontal individuals use different behavioural strategies which might either be related to food availability/competition or genetic control.