Fisheries: Different behaviour of North and Irish Sea cod

Cod (Gadus morhua) are bottom-living, predatory fish of considerable commercial importance, but surprisingly little is known of what cod do for most of their time because it is difficult and costly to study the behaviour of fish at sea. Here we use electronic data-storage tags to investigate the behaviour of cod in the North Sea and in the Irish Sea and find that there are marked differences in the activity of fish in the two regions. This difference could be explained by dissimilar foraging ecology and may have implications for the future management of severely depleted cod stocks.