Quantitative Estimation and Comparison of the Trophic Niches of the Kamchatka Flounder Atheresthes evermanni, the Pacific Halibut Hippoglossus stenolepis, and the Greenland Halibut Reinhardtius matsuurae, by the Isotope Composition of Carbon and Nitrogen of the Food Components

Abstract

The width of trophic niches of the Kamchatka flounder Atheresthes evermanni, the Pacific halibut Hippoglossus stenolepis, and the Greenland halibut Reinhardtius matsuurae have been assessed quantitatively on the Western Kamchatka shelf of the Sea of ​​Okhotsk using the data of isotopic signatures of carbon (δ13C) and nitrogen (δ15N) of their prey. According to the corrected standard ellipse area, the trophic niche widths of the Kamchatka flounder, Pacific halibut, and Greenland halibut are 11.35, 9.41, and 12.36, respectively. The range of δ15N isotopic signatures (8.80–17.61) corresponds to the trophic level 2.63–5.22. According to the limits of variation of δ13C (–14.99… –22.9), the basic carbon sources for halibuts are the prey groups belonging to plankton, nekton, and nectobenthos. The maximum value of the niche overlap belongs to the Kamchatka flounder (93.25%) in the niche of the Greenland halibut; the minimum, on the contrary, belongs to the Greenland halibut (73.19%) in the niche of the Kamchatka flounder. The high degree in similarity of system-wide niche indicators calculated from the isotopic signatures of halibut/flounder prey is balanced by the differences of other parameters in specific habitats: depth, temperature, and food spectra variability in ontogenesis.