Quantification of the demersal marine ecosystem structure in the northern district of the Tohoku sea area, northeastern Japan based on Ecopath approach

Abstract

An Ecopath model for the demersal marine ecosystem (46 functional groups) was constructed based on fisheries resources survey data and commercial fisheries catch statistics in the northern district of northeastern Japan. This is the first Ecopath model for demersal marine ecosystems in the sea area around Japan. We used outputs of the Ecopath model and network analysis tools to quantitatively describe the food web structure and examine the fisheries impacts on the ecosystem. Macrobenthos, mesopelagic fishes, and Pacific krill Euphausia pacifica were identified as important prey species, but prey selectivity of these species differed by predators. Keystone functional groups were demersal sharks, Pacific cod Gadus macrocephalus (2+years), and giant grenadier Coryphaenoides pectoralis. In primary production required (PPR%), Danish seine-trawl fishery was lower than pair-trawl fishery, whereas in relative loss in production (L-index), Danish seine-trawl fishery was higher than pair-trawl fishery.