Histomorphological Abnormalities in Sterlet from the Volga River under Present-Day Ecological Conditions

摘要

The sterlet (Acipenseridae) is an important game and commercial fish. In the past decade, the commercial sterlet stock in the Lower Volga has decreased by more than half, to only 50 metric tons (Kalmykov, 1989; Kalmykov and Kalmykova, 1999). The sterlet population has suffered from so-called ameliorative catching in its upper spawning zone located in the tail race of the Volgograd hydrosystem (Kotlyarevskaya, 1989), as well as from pollution, which results in mass mortality among spawners. The first toxic impact on sterlet in the Volga was observed in July 1965 (Luk'yanenko, 1990), when 180 968 fish died within one week in a segment of the Volga between the villages of Krasnoarmeisk and Seroglazovka. It took ten years to restore the sterlet population. Sturgeons are more sensitive than other fish species to oil pollution (Kasimov and Rustamov, 1968). Water-soluble oil fractions at concentrations of 0.0025 to 0.005 mg/1 induce premature hatching of sterlet prolarvae and their death at late developmental stages. Higher concentrations (0.5-5.0 mg/1) disturb the physiological functions of embryos, which is manifested in an increased protein content, delayed hatching, a high rate of malformations in embryos and prolarvae, and even the total death of larvae (Mikhailova, 1991).