Invaders in the Caspian Sea

Abstract

The Caspian Sea is the largest lake in the world. All its resident species can be considered as invaders with various time of introduction. The most ancient invaders are regarded as indigenous species. The glacial relicts invaded the Caspian 1–1.5 million years BP. There are also “Atlantic species” and those of fresh-water origin. Human-mediated introductions started in the beginning of 20th century. The construction of the Volga-Don Canal facilitated invasion many-fold. A deliberate introduction of fishes and invertebrates has exerted essential influence on the biodiversity of the Caspian in the 1930s–1970s. The impact of introduced species on indigenous biota can be either positive or negative. The invasion of the comb jelly Mnemiopsis leidyi and the bivalve Mytilaster lineatus had negative consequences while deliberate acclimatisation as well as a number of accidental introductions of other aquatic organisms had positive effects. The conclusion was drawn that the most ancient representatives of the Caspian flora and fauna should be protected against any negative impact, including the impact of newly introduced species.