MEPS prepress abstract  -  DOI: https://doi.org/10.3354/meps12508

Ecosystem modeling in the western North Pacific using Ecopath, with a focus on small pelagic fishes

Shingo Watari*, Hiroto Murase, Shiroh Yonezaki, Makoto Okazaki, Hidetada Kiyofuji, Tsutomu Tamura, Takashi Hakamada, Yu Kanaji, Toshihide Kitakado

*Email: swatari@affrc.go.jp

ABSTRACT: Small pelagic fishes like sardine, anchovy and mackerel, play important commercial and ecological roles in the western North Pacific. We present a static, mass-balance “Ecopath” model for this region, focusing on small pelagic fish species, as an initial step to evaluate the role of these fishes in this ecosystem. Our quasi sub-model structure has three blocks, the coastal Oyashio, coastal Kuroshio and offshore, that are established to take sub-regional differences of bottom topography and oceanography into consideration. This model consists of 41 functional groups and assumes that some species are endemic to a block, while some migrating species occur in two or three blocks. We evaluate the quality of our model using pedigree and pre-balance diagnostics. The impact of fisheries on the marine ecosystem assessed by both the L-index, index of loss in secondary production due to fisheries exploitation, and the impact of fisheries targeting small pelagic fishes on the total production of small pelagic fishes, are compared with other ecosystems. Both ecological indices indicate that the western North Pacific ecosystem was not overexploited.