Abstract
Western boundary currents in the subtropics play a pivotal role in transporting warm water from the tropics that contribute to development of highly diverse marine ecosystem in the coastal regions. As one of the western boundary currents in the North Pacific, the Kuroshio Current (hereafter the Kuroshio) exerts great influences on biological resource variability off southwest Japan, but few studies have examined physical processes that attribute the coastal fish resource variability to the basin-scale Kuroshio variability. Using the high-quality fish catch data and high-resolution ocean reanalysis results, this study identifies statistical links of interannual fish resource variability off Sukumo Bay, Shikoku island of Japan, to subsurface ocean temperature variability in the Kuroshio. The subsurface ocean temperature variability off the south of Sukumo Bay exhibits vertically coherent structure with sea-surface height variability, which originates from the westward-propagating oceanic Rossby waves generated through surface wind anomalies in the Northwest Pacific. Although potential sources of the atmospheric variability remain unclarified, the remotely-induced oceanic Rossby waves contribute to fish resource variability off Sukumo Bay. These findings have potential applications to other coastal regions along the western boundary currents in the subtropics where the westward-propagating oceanic Rossby waves may contribute to coastal ocean temperature variability.
Highlights
Western boundary currents in the subtropics contribute to the establishment of rich marine ecosystem along the coastal regions through poleward transport of warm water from the tropics[1]
There are several physical processes proposed to explain the meridional fluctuations of the Kuroshio[11,17,18,19,20,21,22], westward-propagating oceanic Rossby waves from the Northwest Pacific associated with ocean density variations are considered to play an important role in triggering small meanderings off Kyushu island in southwest Japan[19,21,22,23]
Physical processes and predictability of warm water intrusion in Sukumo Bay are well-examined in the previous studies[25,26,27,28,29], but the potential influence on the fish resource variability has yet to be investigated in the context of the links with basin-scale Kuroshio variability
Summary
Western boundary currents in the subtropics contribute to the establishment of rich marine ecosystem along the coastal regions through poleward transport of warm water from the tropics[1]. One of the western boundary currents in the subtropical North Pacific, called the Kuroshio Current (hereafter the Kuroshio), provides favorable environment for highly diverse marine ecosystems off Philippines, Taiwan, and the south of Japan[4,5,6] Since these countries are traditionally dependent on fish resources from the Kuroshio as sources of protein foods, understanding physical processes in the Kuroshio and its potential link with fish resource variability is greatly important. To bridge a gap in our current understanding of the relationship between coastal fish resources and basin-scale ocean current variability, this study aims to (i) establish statistical links of the Kuroshio variability to the fish resources off Sukumo Bay and (ii) identify potential sources of the Kuroshio variability For these purposes, we utilize high-resolution ocean reanalysis results in the Northwest Pacific with the ability to resolve the Kuroshio variability involving mesoscale eddies. The identified relationship would be beneficial for establishing fish resource prediction and management off Sukumo Bay, and have potential applications to other coastal regions along the western boundary currents in the subtropics
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