Distribution of the rare species of clingfishes — small-headed clingfish Apletodon dentatus (Actinopterygii, Gobiesocidae) — near Crimean coasts

Cryptobenthic fauna investigations are highly relevant at studying biodiversity of regions. Studies of the species composition of Gobiesocidae family were carried out in order to clarify ichthyofauna of different regions, and a new species for the Black Sea coastal zone of Crimea was found. Information about its morphology, biology, behavior and other characteristics is very important because of weak study and indeterminate taxonomic status of this species. As a result of morphological studies of the Crimean specimens no significant difference with the type of the Atlantic-Mediterranean populations has been proven. Naturalization of small-headed clingfish in coastal waters of Crimea has been confirmed and some population characteristics, such as a length-weight relationship, have been described. Peculiarities of habitat which which small-headed clingfish prefers and features of localization, enabling competitiveness have been identified. Identification keys were compiled and are given in the paper.