Past of fish resources of the small Aral sea (Kazakhstan)

Abstract

This work is an attempt to trace changes in the fish fauna, their food supply and fish catches in the Small Aral Sea from the beginning of the 20th century to the late 1980s. The purpose of our work is a comparative study of changes in the fishery value of the water reservoir at different stages of its development, including during the last anthropogenic regression. Both literature data and those obtained by the authors in the period 1991–2015 were used. Not only data related to the fauna and fish catches proper, but also data on their food supply, represented mainly by invertebrates, were taken into account. The native ichthyofauna consisted of 20 species of fish, mainly related to benthophages. The biomass of benthos was small — 20 g/m2 due to the significant pressure of fish. The construction of the Tashkent railway was the reason for the emergence of the village of Aralsk in 1905, and the beginning of industrial fishing at sea, as it ensured the export of fish products. The catch of fish in the pre-revolutionary period reached a maximum of 48,300 tons. Planned acclimatization of fish and benthic organisms began to increase the fishery value of the reservoir. Some of them were unsuccessful. The introduction of plankton-eating fish affected not only the zooplankton of the sea, but also its benthic fauna, the abundance and biomass of which decreased. The increase in salinity because of the regression of the water reservoir led to a sharp depletion of the fauna. In the absence of pressure from fish, the biomass of benthic organisms increased by more than 10 times.