Forming Caspian Sprat Stocks in Modern State of the Sea Ecosystem

Abstract

More than 50 years sprat fishing has been a leading trend in the Caspian Sea. Annual catch of sprat species (common kilka, anchovy, big-eyed kilka) reached 440.000 tons. The main fishery object was anchovy sprat. In recent decades anchovy sprat stock has decreased. Common sprat has become main fishery object. There took place redistribution of sprat concentrations in the sea. Middle part of the Caspian Sea has become the general area of commercial stocks of sprat distribution. The cause of these changes was ecosystem deterioration of the Caspian Sea. In this regard, there was made an attempt to generalize the material of many years of ecological monitoring and to determine the degree of impact of outside environment factors on the pelagial ecosystem of the Caspian Sea and forming sprat stocks. According to the analysis results, seismic activity, sea pollution with chemical wastes or petroleum products, sharp increase of the number of unwanted invaders can be considered the factors affecting the habitat of aquatic bioresearches. Closed water reservoirs, circulation of tides, specific ecological features can become the result of transforming separate anomalies into major catastrophes, which will result in decreasing fish productivity of the sea area. One of the problem solutions concerning common sprat commercial stocks decrease is a purposeful struggle against an invader ctenophore-mnemiopsis - the main rival in feeding adult planktivorous fishes and a direct predator for fish spawn and larvae