Fish of the Black sea
The fish fauna of the Black sea is peculiar. The class of fishes that includes about 20 000 species, is divided into two sharply distinct branches — the cartilaginous and bony fish. In the Black sea are mainly of bony fish and only four cartilaginous family: cat sharks, prickly sharks, common stingrays and stingrays. Out of 167 species of sea fish of 37 species is primarily freshwater, 27 – 103 and brackish – marine. A significant part of the primary freshwater species that live in coastal lakes and river estuaries, can tolerate some salinization of water. Many of them (several species of herring, almost all servie fish, etc.) are semi-migratory and passage species, and some species are fully adapted to marine conditions of life.
Most of the group of brackish-water fishes of marine origin can withstand large desalination, and others (several species of gobies, etc.) live in fresh water. It is autochthonous relict species characteristic of the Ponto-Caspian basin. Their origin is connected with seas that filled the black sea geosyncline during the Neogene. In the third group — marine fish — can distinguish 8 species of boreal-Atlantic relicts, while the remaining 95 species belong to Mediterranean immigrants, who make up 57% of the species inhabiting the Black sea.This group includes primarily heat-loving species migrated from the Mediterranean sea.
The majority of immigrants (anchovy, mackerel, sprat, etc.) found good living conditions in the Black sea and managed to develop numerous populations. Some species have not fully adapted to the conditions of the Black sea. So, Bonito and lofar breed and feed in the Black sea, and winter in marble. There are some species that accidentally enter through the Bosphorus into the Black sea.
The Bulgarian coast is known 140 species of fish and 25 freshwater and brackish-water inhabiting in coastal lakes and estuaries, autochthonous 20 — 16 (4 mackerel species, 11 species of gobies and 1 species of shark) are primarily marine and 4 species (sturgeon) is primarily freshwater and 95 species of Mediterranean immigrants — including 8 species of boreal-Atlantic relicts.