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
Blue whale Naturae" of 1758, would have known this and may have intended the ironic double meaning. Herman Melville called this species "sulphur-bottom" in his novel "Moby-Dick" (1851) due to an orange-brown or yellow tinge on the underparts from diatom films on the skin. Other common names for the blue whale have included "Sibbald's rorqual" (after Sibbald, who first described the species), the "great blue whale" and the "great northern rorqual". These names have now fallen into disuse. The first known usage of the term "blue whale" was in Melville's "Moby-Dick", which only mentions it in passing and does not specifically attribute