Review of the Distribution of the Family Gobiidae (Pisces) in the Bulgarian Danube Tributaries

The current study aims to give in detailed information on the actual distribution of the species from family Gobiidae in the Bulgarian Danube tributaries. All known literature has been revised and with the new data collected is given complete and actual information on their distribution. In the period 2010-2012 were sampled a total of 41 sites alongside each one of the Bulgarian Danube tributaries. The sampling started from the river mouths to upstream in order to discover what is the southern (upstream) distribution of each one goby species. Four goby species were recorded from the tributaries – the round goby (Neogobius melanostomus Pallas, 1814), the monkey goby (Neogobius fluviatilis), the racer goby (Neogobius gymnotrachelus) and the tubenose goby (Proterorhinus marmoratus). Further analysis showed preference of mixed substrates and silt in addition of homogenous ones. The occurrence of gobies in the studied tributaries decreased inversely proportional to distance from Danube.