INTRODUCED AND INVASIVE FISHES IN THE INLAND WATERS OF UZBEKISTAN (ARAL SEA BASIN): PATHWAYS, ESTABLISHMENT, GROWTH AND ECOLOGICAL IMPACTS: A REVIEW

Abstract

The inland waters of Uzbekistan, which lie almost entirely within the Aral Sea basin, have been profoundly reshaped by a century of fish introductions. Alongside a native fauna of more than seventy species — many of them Central Asian endemics — several dozen fishes have been added, both deliberately, through twentieth-century acclimatisation and aquaculture programmes, and accidentally, as contaminants of stocked material. A substantial subset of these introductions has established self-reproducing populations and now behaves invasively, competing with and preying upon native and endemic fishes. This review synthesises the available literature on the introduced and invasive fishes of Uzbekistan, with emphasis on the Syr Darya drainage and the reservoir- rich waters of the Tashkent region. We summarise the scale and pathways of introduction; profile the principal invaders — the Chinese hook snout Opsariichthys bidens, topmouth gudgeon Pseudorasbora parva, sharpbelly Hemiculter leucisculus, Prussian carp Carassius gibelio and eastern mosquitofish Gambusia holbrooki; review what is known of their growth, condition and stock; and assess their impacts on the native ichthyofauna. We highlight that quantitative data on the stock, growth and condition of invasive fishes in the region — particularly in reservoirs — remain fragmentary, and we identify this as a priority for research and management. Recent length–weight studies suggest that some invaders grow especially robustly in reservoir habitats, a trait that may accelerate their spread through the regulated rivers of Central Asia.