BIOLOGIYA MORYA, 2022, Vol. 48, No. 3, pp. 160-170

Trophic Relationships of Sympatric Fish Species of the Genera Opisthocentrus and Pholidapus (Perciformes: Opisthocentridae) in the Sea of Japan

© 2022 O. A. Rutenko^{1, 2}, V. N. Ivankov¹, S. I. Kiyashko², N. A. Nekrasova¹

¹Laboratory for Ecology and Evolutionary Biology of Aquatic Organisms, Institute of the World Ocean, Far Eastern Federal University, Vladivostok 690922, Russia;
²A.V. Zhirmunsky Institute of Marine Biology, National Scientific Center of Marine Biology, Far Eastern Branch, Russian Academy of Sciences, Vladivostok 690041, Russia

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Trophic relationships of four sympatric fish species of the family Opisthocentridae (Perciformes)- Opisthocentrus ocellatus, O. tenuis, O. zonope, and Pholidapus dybowskii - were studied by analyzing their stomach contents and signatures of stable nitrogen and carbon isotopes (δ¹⁵N and δ¹³C) in soft tissues. The mean carbon isotope signature values ranged from -20.04 ± 0.95 to -15.44 ± 0.98, which indicated a wide range of primary carbon sources. The highest mean nitrogen isotope signature values (10.71 ± 0.55) and the maximum isotopic niche width were recorded for Ph. dybowskii. Amphipods are the major food item of all the fish species under study, which was confirmed by a significant overlap of their isotopic niches. The partitioning of trophic niches is explained by the selective consumption of prey crustaceans that are specific to each of the fish species, and also by the use of aquatic invertebrates from different taxonomic groups as an additional food supply. The Schoner's similarity index, calculated on the basis of relative abundances of food items identified to species, showed no competitive relationships between all of the fish species under study. The values of the index between the most phylogenetically close species O. ocellatus and O. tenuis were minimum.

Key words: Opisthocentrus, Pholidapus, trophic relationships, diet range, food bolus structure, stable isotopes, carbon, nitrogen.