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
Ide (fish) the wild in at least one site within New Zealand. Ide occurs in schools in the clear pools of larger rivers, ponds, and lakes but they may move to deeper waters during the winter before moving into shallow freshwater to spawn in the spring. The species is also found in the Baltic Sea, which has a lower salinity than most seas and in Sweden the fish spent the first year of their lives in rivers before joining the more mature fish as they migrated downstream into the Baltic Sea during the summer months. The fish then returned to the rivers