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
Fish species of the Neretva basin its many tributaries, lakes and marshes provides rich freshwater habitat for its native, as well as for introduced non-native fish species. There are deep canyon as well as wide valley sections with both fast flowing rapids with side-pools, and narrow sections with deep, still waters running slowly. The flowing water can be any combination of fast or slow, deep or shallow, open or protected by canyons, rocks, tree roots and undercut banks, and shaded by vegetation on the bank or exposed to full sunlight. This variation ensures that a relatively large number of fish species are able to find suitable