Danube bleak by the building of dams across many of the rivers. Landlocked populations survive in small rivers and reservoirs, breeding in the small streams above the dams. The main Caspian Sea population has found ways of spawning below the dams. Overfishing and pollution in the Caspian Sea could impact on the Danube bleak but in 2008 the IUCN Red List of Threatened Species listed it as being of "Least concern". The Danube bleak feeds on small crustaceans, worms, molluscs, insect larvae, insects and small fish. Male Danube bleaks assemble in May to July at spawning sites in fast flowing streams with
Cryptid whale Another argued hypothesis is that that pod was part of an inbred population, which led to the mutation. Another possibility is that Quoy and Gaimard observed specimens which were neither deformed nor members of an unknown species or population, but rather mistaken identification of a pair of beaked whales that, by perspective, appeared to be one single creature. The high-finned sperm whale, or the high-finned cachalot, is an alleged variant or relative of the known sperm whale, "Physeter macrocephalus", with an unusually tall dorsal fin from the North Atlantic. The physician Sir Robert Sibbald, in 1687, described an alleged stranded