Possibility of using goby fishes (Gobiidae) as indicators of the state of the coastal ecosystems of the Black and Azov Sea and the impact of climate change on them

Abstract

In the ichthyofauna of the northern coast of the Black Sea-Azov basin, goby fish (Gobiidae) have the largest number of species and are found on different substrates. Among them there are representatives of two groups of different origins: 1 – Ponto-Caspian relics and 2 – Mediterranean immigrants who began to move in the Black Sea after its last connection with the Mediterranean. The primary is the fauna of goby fish of Ponto-Caspian origin, to which, due to climate warming and an increase in salinity, Mediterranean goby immigrants have gradually added. Among the Ponto-Caspian relics, 10 species can be classified as marine ones, which survive at salinity up to 12–15 ‰ and higher. There are 26 species of gobies that are found in sea waters with a salinity of 15–18 ‰. A goby (gobiid) coefficient is proposed – the ratio of the number of Mediterranean immigrant goby species to the number of Ponto-Caspian relic sea goby species, which can be considered as the mediterranization index of goby fish fauna. This index also reflects the trends towards changes in the entire marine ichthyofauna of the Black Sea-Azov basin against the background of a progressive warming of the climate. Three regions are distinguished by climatic conditions, temperature and salinity of water off the northern coast of the Black and Azov Seas. For the northwestern part of the Black Sea, the mediterranization index of the goby fish fauna is currently 0.7; for the southwestern and southern coasts of Crimea – 1.6; for the Kerch pre-strait area and the Sea of Azov – 0.5. With the emergence of new species of Mediterranean immigrant gobies in each of the regions, the indicators of the mediterranization index will increase.