The Cod Population Off the Coast of Sweden is not Extinct

Published:20 Feb.2023 Source:ScienceDaily

By genetically analysing cod collected by test fishing, researchers have found that there are two distinct types of cod living in the waters along Sweden's west coast. The two types of cod found off the west coast are known as 'offshore cod' and 'coastal cod', because one has its origins far out to sea, while the other resides close to the coast throughout its life. These two types of cod rarely mate with each other. Many people have long believed that the west coast's coastal cod have been completely fished out. But this new study, published in the ICES Journal of Marine Science, shows that there is still a cod population that spends all its life off the west coast of Sweden.

For the study, the researchers collected juvenile, decimetre-long, cod from over 100 different sites in the Skagerrak, the Kattegat and the Sound (Öresund), and analysed them genetically. Their results show that the cod stock in the area is not just made up of offshore cod, but is a mixture of both ecotypes. Offshore cod are found mainly far off the coast and the coastal cod closer to the shore. In the fjords of West Sweden, the proportion of coastal cod is very high, which is a little unexpected given the theory that they were virtually extinct. In some places both offshore and coastal cod are found in the same fjord, but they appear to live at different depths. Offshore cod live at slightly greater depths, while coastal cod are more common in shallow waters.