ОСОБЕННОСТИ НЕРЕСТОВЫХ МИГРАЦИЙ ПРОХОДНЫХ ВИДОВ РЫБ КАСПИЙСКОГО МОРЯ ЧЕРЕЗ МОРСКОЙ СУДОХОДНЫЙ КАНАЛ ЗА ПЕРИОД 2001–2022 ГГ.

Abstract

Background. Anadromous species of sturgeons, salmonids and clupeids inhabiting the Caspian Sea migrate to their spawning grounds predominantly through the Volga-Caspian Sea Shipping Canal (VCSSC), which hydrological and hydrographic features have an effect on the abundance dynamics of the anadromous fish species. Along the entire delta sea edge, the Volga-Caspian Sea Shipping Canal (around 200 km in length) provides the conditions required for fish migration. Relevance. The current decrease in the Caspian Sea level and extensive accumulation of the fluvial and marine drift sediments impede navigation due to insufficient depth of the waterway and affect the entering of the anadromous breeders. This work is aimed at the assessment of the VCSSC use by sheefish, black-spined herring, beluga sturgeon, Russian sturgeon and stellate sturgeon during various seasons within 2001–2022 time range. Methods. Trawling and net fishing have been conducted in the marine part of the canal. Based on the data from seine catches in the river, the seasonal dynamics of fish migrations has been identified. Results. Despite the existence of extensive riverine network of the River Volga Delta suitable for the entering of anadromous fish species (Kirovsky, Belinsky, Igolkinsky, Karaysky and other banks), the Volga-Caspian Sea Shipping Canal (Main Bank) provides the anadromous fish species with a primary transit waterway to their spawning grounds—up to 90 % sheefish and black-backed herring breeders out of the total spawning stock abundance. The share of stellate sturgeon migrating along this waterway is 76–78 %, for the Russian sturgeon it is 83–85 %, and for beluga sturgeon it is 90–95 % of the spawning populations in the year of their entering into the Volga River. In recent years, the ecosystem of the Volga River has been developing in the context of low water content, which leads to the decrease in the water level of fish passage channels and tj a weakened flow, which, exacerbated by abiotic factors, in turn results in the reduction in the spawning stock abundance and decline in the yield of juveniles of the anadromous fish species [1]. Conclusion. During their pre-spawning season, sturgeons, sheefish and anadromous herring use the Volga-Caspian Sea Shipping Canal as the main migratory passageway to their spawning grounds. After the spawning, the canal provides juveniles and mature breeders with the passageways to the feeding sites in the Northern Caspian Sea. Sturgeon juveniles and the individuals skipping the spawning actively feed in the marine part of the canal [2].