Danube bleak branched rays while the anal fin has fifteen to nineteen. This fish is morphologically quite variable which may be due to local adaptations to various habitats but is more likely to be due to several species being involved. The Danube bleak occurs in slow flowing stretches of rivers flowing into the Black Sea and the Caspian Sea and in the Aral Sea basin, in Alpine rivers among others. It is a migratory fish, spawning in the headwaters of the rivers and then moving down to the lower parts, estuaries and brackish areas of sea. These migratory patterns have been disrupted
Whale Monodontidae (belugas and narwhals), Physeteridae (the sperm whale), Kogiidae (the dwarf and pygmy sperm whale), and Ziphiidae (the beaked whales). Whales are creatures of the open ocean; they feed, mate, give birth, suckle and raise their young at sea. So extreme is their adaptation to life underwater that they are unable to survive on land. Whales range in size from the and dwarf sperm whale to the and blue whale, which is the largest creature that has ever lived. The sperm whale is the largest toothed predator on earth. Several species exhibit sexual dimorphism, in that the females are larger