When designed and built without adequate attention to the natural functioning of a river, dams have the effect of cutting a river into ecologically isolated compartments, which do not allow free movement and migration of species. Migratory fish are particularly badly hit, being rendered unable to move upstream or downstream between their spawning grounds and areas used at other times in their life cycle. The construction of the Iron Gates had a major impact on the local fauna and flora as well—for example, the spawning routes of several species of sturgeon were permanently interrupted. Beluga sturgeon was the largest, and the largest specimen was recorded in 1793, at . There have also been significant regional economic impacts – notably on the productivity of Danube fisheries. The status of the Danube’s migratory fish species is a strong indicator of the ecological health of the entire Danube River Basin, which in turn has wider economic and strategic consequences.