Formerly the fourth largest lake in the world with an area of 68,000 km

Ecology

Native fish

Despite its former vast size, the Aral Sea had relatively low indigenous biodiversity. However, the Aral Sea basin had an exceptional array of endemic fish subspecies (as well as the three endemic sturgeon species), most of which still survive in the North Aral Sea, but some such as the sturgeons have been extirpated or even driven extinct by the lake's shrinkage. Native fish species of the lake included ship sturgeon (Acipenser nudiventris), all three Pseudoscaphirhynchus sturgeon species, Aral trout (Salmo trutta aralensis), northern pike (Esox lucius), ide (Leuciscus idus oxianus), asp (Aspius aspius iblioides), common rudd (Scardinius erythropthalmus), Turkestan barbel (Luciobarbus capito conocephalus), Aral barbel (L. brachycephalus brachycephalus), common bream (Abramis brama orientalis), white-eyed bream (Ballerus sapa aralensis), Danube bleak (Chalcalburnus chalcoides aralensis), ziege (Pelecus cultratus), crucian carp (Carassius carassius gibelio), common carp (Cyprinus carpio aralensis), Wels catfish (Silurus glanis), Ukrainian stickleback (Pungitius platygaster aralensis), zander (Sander lucioperca), European perch (Perca fluviatilis), and Eurasian ruffe (Gymnocephalus cernuus). All these fish aside from the stickleback lived an anadramous or semi-anadromous lifestyle.

The salinity increase and drying of the lake extirpated the Aral trout, ruffe, Turkestan barbel and all sturgeon species, and dams now block their return and migration routes, with the Aral trout and Syr Darya sturgeon (Pseudoscaphirhynchus fedtschenkoi) possibly extinct due to their restricted range. All other native fish barring the stickleback (which persisted during the lake's shrinkage and salinity increase) were also extirpated, but have returned to the North Aral Sea following its recovery from the 1990s onwards.