Rediscovery of rare shovelnose sturgeons in the Amu Darya River, Uzbekistan
Аннотация
The small Amu Darya shovelnose sturgeon Pseudoscaphirhynchus hermanni (Acipenseridae) is a small, rare sturgeon species known only from the Amu Darya River in Central Asia. It was last caught in 1996, in the middle reaches of the river (Salnikov et al., 1996, The Sturgeon Quarterly, 4, 10–14), and had not been recorded in its lower reaches since 1982 (Zholdasova, 1997, Environmental Biology of Fishes, 48, 373–380). After the drying of the Aral Sea, habitat alterations in the Amu Darya River (overfishing, damming and channel management, extraction of water for irrigation, and water pollution) have led to a severe decline of sturgeon species there. In 1996, P. hermanni was categorized as Critically Endangered on the IUCN Red List. On three occasions in 2020 (18–21 January, 14 March and 3 August), we searched for this species in the lower reaches of the Amu Darya. In a 55 km stretch of the river in the Khorezm Region of Uzbekistan, we collected five fish with the typical morphology of P. hermanni (i.e. a dark morph with a short snout). In addition, we caught four individuals of the Amu Darya shovelnose sturgeon Pseudoscaphirhynchus kaufmanni, which is also Critically Endangered. Pseudoscaphirhynchus hermanni can be distinguished from P. kaufmanni by its lack of a caudal filament, lack of spines on the snout, a shovel-shaped snout, pectoral fins with a fold that curls dorsally, and its small size. Although they are rare and probably declining, our findings confirm that both P. hermanni and P. kaufmanni are still present in the Amu Darya River. Unfortunately, there has been no known reproduction of these species in captivity. Conservation efforts for both species are needed urgently.