Adaptive mechanisms of distribution and population dynamics of Carassius auratus gibelio in the Ponto-Caspian region (with reference to the Azov basin)

Abstract

Historically, from the beginning of the 20th century until the beginning of the 21st century, an attempt was made to discern the major adaptive mechanisms that determine the distribution and population dynamics of the silver crucian carp Carassius auratus gibelio (Bloch, 1782) in the Ponto-Caspian region at various stages of freshwater and coastal marine ecosystem functioning with reference to the Azov basin (including introduction of Carassius auratus gibelio from the Amur basin into natural waterbodies of this region as well as rapid development of pond fish farming with introduction of Carassius auratus gibelio as an additional object of aquaculture). Until the middle of the 20th century, Carassius auratus gibelio was a secondary component of freshwater and lagoon ichthyocenoses of the Azov basin. Its populations were represented by the gynogenetic form. At present, owing to transformation of the genetic structure and domination of the bisexual form of Carassius auratus gibelio, the dependence controlling reproduction of the formerly prevalent unisexual-female form by direct connection with abundance and spawning dates of related cyprinid species disappeared. In 1980–1998, there was a quantitative outbreak and area expansion of Carassius auratus gibelio in the Azov basin owing to freshened waters of the Taganrog and Temryuk bays of the Sea of Azov. Owing to multiple spawning, a broad food spectrum, and high resistance to pollutants, Carassius auratus gibelio actively colonizes new biotopes vacated by former major components of ichthyocenoses of the Azov basin. At present, catches of Carassius auratus gibelio definitely belong to the top three semifreshwater fish of the Russian part of the Azov basin. In the years of the outbreak, Carassius auratus gibelio living in the Temryuk Bay makes, under favorable hydrological conditions, extensive spawning migrations via the Kerch Strait along the Black Sea coast of Taman Peninsula.