A Comparative Study of Feeding Ecology and Trophic Relationships of Bothrocara brunneum and B. zestum (Zoarcidae) from Northwest Pacific Deep-Sea Ecosystems

The results of analysis on the feeding patterns and assessment of the trophic levels and niches in two Zoarcidae species Bothrocara brunneum and B. zestum from the deep-water areas in the Sea of Okhotsk and the Pacific Ocean off the Lesser Kuril Ridge have been reported. Both species feed on various benthic and mesobenthic forage organisms including crustaceans, mesopelagic fishes, cephalopods, bivalved mollusks, polychaetes, and echinoderms. Despite the dominant food component variability across different water areas, crustaceans represent the major food group. In addition, both fish species have similar food sources and, therefore, trophic niches. It is proven by estimation with the standard ellipse area method via the Bayesian probability, showing rather similar widths of trophic niches: 17.7 for B. zestum and 16.6 for B. brunneum. The actual values for stable nitrogen isotope ratios (δ¹⁵N) in food components indicate a wide range of trophic levels in the analyzed species: from 2.08 to 4.36 in B. zestum and from 1.97 to 4.42 in B. brunneum, which can prove their plasticity in selecting the food items. The ranges of values for the stable carbon isotope ratios (δ¹³C) in food components indicating the basal food sources reached 15.04 to 23.43‰ for B. zestum and 15.07 to 23.43‰ for B. brunneum. The survey-based new information on two species feeding was obtained to determine their roles in the trophic structures of ecosystems in the studied water areas.