Baltic Sea as species in 2005 and 2018 respectively, having formerly been confused with more widespread relatives. The tiny Copenhagen cockle ("Parvicardium hauniense"), a rare mussel, is sometimes considered endemic, but has now been recorded in the Mediterranean. However, some consider non-Baltic records to be misidentifications of juvenile lagoon cockles ("Cerastoderma glaucum"). Several widespread marine species have distinctive subpopulations in the Baltic Sea adapted to the low salinity, such as the Baltic Sea forms of the Atlantic herring and lumpsucker, which are smaller than the widespread forms in the North Atlantic. A peculiar feature of the fauna is that it contains a
Migration of marine species in the Northern Atlantic Ocean outside their normal range and into more northern waters causing an array of ecological, economic, and fishery management problems. William Cheung, a professor at the University of East Anglia, in the Sea Around Us Project at the University of British Columbia concluded that the oceans were warming at an average of per decade and at per decade in tropical waters. However, the north-east Atlantic has been warming at a rate of per decade. Cheung and his colleagues were able to get these estimates by using the mean temperature of catch. They used data from 990 species within 52 marine ecosystems