Cod in a sweat: some like it hot!

Scientists at CEFAS (UK) have found that the migration pattern of wild cod is much less restricted by environmental temperature than laboratory studies suggest. Previously, research in the lab indicated that the preferred temperature range of cod was between 11-15ºC. However scientists following movements of wild cod equipped with electronic tags that record depth and temperature have found that whilst some fish prefer deeper cooler waters, others tagged at the same time prefer to swim in shallower habitats in the Southern North Sea where summer temperatures are consistently above 17ºC. Dr Julian Metcalfe will be presenting the latest results of the EU-funded CODYSSEY project at the Annual Meeting for the Society for Experimental Biology on Monday 3rd April [session A3].

“We have found that cod in the northeast Atlantic repeatedly experience abrupt temperature changes of up to 8ºC, suggesting that temperature may not be so crucial in constraining the movements and distribution of adult cod”, explains Dr Metcalfe, “However this doesn’t mean that climate change won’t impact the numbers or distribution of cod populations since there may be other environmental factors such as prey distribution that could be affected by a rise in sea temperatures”.

This work is from a large EU-funded project called CODYSSEY which aims to identify key environmental forcers of horizontal movements of cod. To date the programme has tagged and released over 2500 wild-caught cod across the North Sea, Barents Sea, Baltic Sea Faeroese waters and Icelandic waters. Seventeen percent of these tags have so far been returned. In the future the researchers plan to study other key species of interest to UK and EU fishermen.