A fish declared extinct
The ship sturgeon, Acipenser nudiventris, is an ancient fish. Its ancestors swam in the rivers of Central Asia when dinosaurs still walked the Earth. For millennia, it thrived in the vast Aral Sea basin, migrating up the Syr Darya river to spawn. This changed in the 1960s when Soviet planners diverted the Amu Darya and Syr Darya rivers to irrigate cotton fields. This massive water diversion project began one of the 20th century's most severe ecological disasters.
The Aral Sea, once the world's fourth-largest lake, began to shrink. As freshwater inflow was cut off, the lake's salinity skyrocketed. Before the 1960s, the water had a salinity of about 10 grams per liter; by 2004, parts of the sea reached 92 grams per liter, nearly three times saltier than the ocean. This hyper-saline water was lethal to freshwater species. The Aral Sea's fish populations collapsed, with commercial catches falling from 43,430 tons in 1960 to zero by 1980. The ship sturgeon, unable to survive in the toxic, salty water, was declared extinct in the Aral Sea basin.
An unexpected survivor
For decades, the ship sturgeon was believed to be gone from the region forever. The species is critically endangered globally, with only a few remnant populations in places like the Ural River. But the Syr Darya river held a secret. Isolated from the hyper-saline remnants of the South Aral Sea, a small, resilient population of ship sturgeon had survived in the river's freshwater reaches.
The turning point for the ecosystem came in 2005 with the completion of the Kok-Aral Dam. This 13-kilometer-long structure, built by Kazakhstan with support from the World Bank, separated the northern part of the Aral Sea from the desiccating southern part. The dam allowed the Syr Darya's flow to accumulate, stabilizing the North Aral Sea. Water levels rose, and salinity dropped dramatically, from over 30 g/L back down to around 8 g/L.
This restoration allowed the return of more than 20 freshwater fish species. Among them was the ship sturgeon. While still exceptionally rare, this remnant population now has a chance. The recovering ecosystem in the North Aral Sea provides a habitat that had been lost for half a century. These fish are true survivors of an environmental collapse, a link to the Aral Sea's healthier past. Specimens can grow to over 2 meters long, weigh up to 80 kg, and live for decades. Their continued presence in the Syr Darya shows the resilience of life and the positive impact of targeted ecological restoration.