Supporting agencies: The paper summarizes the results of the work on the Russian Foundation for Basic Research (RFBR) project № 19-15-50012. The author used also her materials obtained during the surveys performed as a part of the RSF № 16-17-10103 (Ponto-Caspian region), RFBR № 18-00-00470 and № 20-39-70020 (Eastern Caspian region) and RFBR № 18-05- 00296 (Strait of Kerch) projects. The author is thankful to all her colleagues who took part in the survey in the region.