Elizabeth Grace Tunka BENGİL, Mehmet AYDIN

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

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.

Güney Karadeniz’den kayabalığı Mesogobius batrachocephalus (Pallas, 1814) türünün boy-ağırlık ilişkileri ve beslenme ekolojisi

Ekolojik olarak çok çeşitlilik gösteren kayabalığı türlerinden, daha önce Gobius batrachocephalus olarak bilinen kayabalığı Mesogobius batrachocephalus (Pallas, 1814) türü Karadeniz endemiği bir türdür. Karadeniz’de türün biyolojik özellikleri üzerine çalışmalar bulunmasına karşın Karadeniz’in Türkiye kıyılarından sadece boy-ağırlık ilişkilerine dair çalışmalar bulunmaktadır. Bu çalışma Karadeniz’de türün boy-ağırlık ilişkisi ve beslenme ekolojisi üzerine olan bilgi eksikliğine katkı sağlamayı hedelemektedir. Toplamda 470 birey toplanmış olup daha önce negatif (-) allometri gösterdiği rapor edilmiş olan kayabalığının bu çalışmada bahar döneminde negatif (-) ve diğer mevsimlerde positif (+) allometri gösterdiği tespit edilmiştir. Besinini krustaseler, teleost balıklar ve gastropodlar oluşturmaktadır. Göreceli önemlilik indeksi analizine göre tüm bireyler ve erkekler için teleost balıklar ve dişiler için krustaseler ana besin grubunu oluşturmaktadır. Tüm bireyler için trofik seviye 4.34 bulunmuş olup dişilerin erkeklerden daha yüksek trofik seviyeye sahip olduğu gözlemlenmiştir. Yazın her iki cinsiyette sadece teleost balıkları tercih etmelerine karşın diğer mevsimlerde dişiler erkeklerden daha çok krustaseleri tercih etmektedir. Niş genişliği indeks sonuçlarına göre mevsimler karşılaştırıldığında kışın en geniş ve yazın en dar olduğu, dişilerin sonbaharda ve erkeklerin kışın en geniş sonuçlara sahip olduğu bulunmuştur. Sonuç olarak, türün beslenme ekolojisi mevsimsel ve eşeyler arası değişiklik göstermekte ama genel besin grupları aynı kalmaktadır.

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