The length and weight relationships and feeding ecology of knout goby, Mesogobius batrachocephalus (Pallas, 1814) from Southern Black Sea

Abstract

Among ecologically diverse gobies species, knout goby, Mesogobius batrachocephalus (Pallas, 1814), or previously known as Gobius batrachocephalus, is a Black Sea endemic species. There are studies on this species biological features along the Black Sea but there are only studies on its length and weight relationship along the Turkish coasts of the Black Sea. This study aims to contribute to the lack of knowledge on knout goby length and weight relationship and feeding ecology inhabiting Southern Black Sea. Total of 470 individual of knout goby was collected and it was previously reported that knout goby shows negative (-) allometry though within this study it was found that it only shows negative (-) allometry in spring and positive (+) allometry in other seasons. The diet was composed of crustaceans, teleost fishes and gastropods. According to the relative importance analysis, teleost fishes are the main food item for all and male individuals but for female crustaceans are the main food item. Trophic level results show that for all individuals trophic levels is 4.34, and when sexes are compared females have higher trophic level than males. While both sexes only consume teleost during summer, in other seasons females prefer more crustacean in their diet compared to males. Niche breadth index results indicated that when all individuals diet was compared among seasons in winter the niche breadth was the broader and summer was the narrower, in case of females the broader was fall and for males it was winter. In conclusion, feeding ecology of knout goby changes between seasons and sexes but general prey groups remain the same