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
Pacific barracuda however, when young, Pacific barracuda are found in bays in shallow waters. However, some Pacific Barracuda have been recorded to be found in deep waters, about 37 m. The Barracuda are known to form schools and move across the ocean in these schools of fish. However, in some larger species, it has been noted that they can be found swimming solitarily. The Pacific barracuda are a predatory fish, exhibiting aggressive behavior in order to feed on other small fishes. Their diet primarily consists of small fish such as anchovies, small pacific mackerels, grunions, squid, groupers, grunts, and even young barracuda.