Diet of the round goby, Neogobius melanostomus, in artificial and natural habitats in Noshahr coasts

In recent decades, coastal artificial structures have been increased in response to increment of storms, and coastal settlement. Round goby belong to family Gobiidae, one of the most important fish families in the Caspian Sea because of their abundance. In this study, we compared the feeding strategy and species diversity diet of the round goby, Neogobius melanostomus between artificial shores (Riprap structures) and natural shores including gravel and stony shores. According to the results, overall ten prey items consist of Xanthidae, Palaemonidae, Gammaridae, Amphibalanus improvisus, Ostracoda, Nereis diversicolor, Bivalvia, Foraminifera, fish remains and fish eggs were observed in the diet of round gobies. In artificial, gravel and stony shores, A.improvisus (%19.37), Ostracoda (%78.44) and N.diversicolor (%1.42) were most abundant food items. Analysis of the digestive tract contents revealed that round gobies consume wide spectrum of distinct food items in different shores. individuals of the fish have more specialized on distinct prey items at the artificial rocky shores in comparison with the other shores. At the artificial shores, round gobies are specialized on fish eggs, Ostracoda, Palaemonidae, Amphibalanus improvisus, Nereis diversicolor, Foraminifera and Xanthidae. 10, 8 and 6 prey items were observed in the diet of round gobies at the artificial rocky, gravel and sandy shores, respectively. Comparison of the species diversity in the gut contents of round goby showed higher value (1.94) at the artificial rocky shores than the gravel (1.62) and sandy (1.55) shores but, there was no significant difference in shannon index between artificial and natural shores.