The Danube salmon is a territorial species, but not solitary, with large individuals occupying and defending territories such as a large pool, which may be inhabited by several other individuals (2) (6). These fish undertake short migrations upstream for spawning between April and May (2) (5). Here, females make a pit in the gravel, in which the male fertilises the eggs (5). One female mates with one male, which warns off other males that approach. The length of incubation depends on water temperature, but larvae generally hatch 16 to 24 days after the eggs are ‘activated’ by appropriate water temperatures (6). Individuals then proceed to grow very rapidly, reaching sexual maturity by between four and six years of age (5). Juveniles feed primarily on invertebrates such as insect larvae, whilst adults prey mostly on fish, but also on amphibians, reptiles, small mammals and waterfowl (6).