<P> Since the Baltic Sea is so young there are only two or three known endemic species: the brown alga Fucus radicans and the flounder Platichthys solemdali . Both appear to have evolved in the Baltic basin and were only recognized 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 . </P> <P> A peculiar feature of the fauna is that it contains a number of glacial relict species, isolated populations of arctic species which have remained in the Baltic Sea since the last glaciation, such as the large isopod Saduria entomon, the Baltic subspecies of ringed seal, and the fourhorn sculpin . Some of these relicts are derived from glacial lakes, such as Monoporeia affinis, which is a main element in the benthic fauna of the low - salinity Bothnian Bay . </P> <P> Cetaceans in Baltic Sea have been monitored by the ASCOBANS . Critically endangered populations of Atlantic white - sided dolphins and harbor porpoises inhabit the sea where white - colored porpoises have been recorded, and occasionally oceanic and out - of - range species such as minke whales, bottlenose dolphins, beluga whales, orcas, and beaked whales visit the waters . In recent years, very small, but with increasing rates, fin whales and humpback whales migrate into Baltic sea including mother and calf pair . Now extinct Atlantic grey whales (remains found from Gräsö along Bothnian Sea / southern Bothnian Gulf and Ystad) and eastern population of North Atlantic right whales that is facing functional extinction once migrated into Baltic Sea . </P> <P> Other notable megafauna include the basking sharks . </P>

Can you see whales in the baltic sea