Abstract
Climate-change associated changes in oceanographic conditions, particularly sea surface temperatures (SSTs), have systematically affected many marine fisheries resources around Japan. The Pacific Decadal Oscillation (PDO) index is considered one of the most important climate indices for describing basin-scale SST variations in the North Pacific, which are closely related to decadal variations in fisheries resources. Time series of the PDO index has been used to conventionally classify decadal conditions of ocean and fisheries resources around Japan as either warming or cooling regimes. It is now clear that for the 2000s to the mid-2010s, mostly during the “global surface warming slowdown,” the SST regime around Japan was unconventional; despite the PDO index being in a negative phase, which normally corresponds to a warming regime around Japan, SSTs exhibited decadal cooling in some waters and seasons. SSTs in the western part of the North Pacific subtropical gyre gradually decreased, particularly in autumn–spring, whereas SSTs in the western subarctic gyre and the Sea of Okhotsk increased. Moreover, SSTs between the subtropical and subarctic waters around northern Japan exhibited seasonal contrasts that were decadally intensified through the combined effects of cooling in winter–spring and warming in summer–autumn. Some major marine fisheries resources around Japan showed decadal increases or decreases beginning in the mid-2000s, and appeared to respond to the unconventional SST changes in their early life stages. In this paper, we review atmosphere and ocean conditions around Japan in the 2000s–2010s in terms of global climate, present an overview of potential impacts of decadal SST trends on five major commercial fisheries resources (walleye pollock, chum salmon, Japanese sardine, Japanese anchovy, and Japanese flying squid), and raise awareness that an unconventional regime can appear transiently during a state of global warming.
Highlights
The Japanese archipelago is located along the Kuroshio–Oyashio western boundary current region in the North Pacific Ocean and surrounded by the eighth largest exclusive economic zone (EEZ) in the world, including parts of the North Pacific, East China Sea, Sea of Japan, and Sea of Okhotsk (Figure 1A)
The data for commercial fisheries resources considered in this study, except for chum salmon Oncorhynchus keta, were derived from the latest stock assessment reports for the Japanese Pacific stock (JPS) of walleye pollock Gadus chalcogrammus (Sakai et al, 2020), the Pacific stocks of Japanese sardine Sardinops melanostictus (Furuichi et al, 2020) and Japanese anchovy Engraulis japonicus (Kamimura et al, 2020), and the winter spawning stock of Japanese flying squid Todarodes pacificus (Kaga et al, 2020)
sea surface temperature (SST) decreases were localized near the polar front along 40◦N in the Sea of Japan and the Oyashio/subarctic front in the North Pacific
Summary
The Japanese archipelago is located along the Kuroshio–Oyashio western boundary current region in the North Pacific Ocean and surrounded by the eighth largest exclusive economic zone (EEZ) in the world, including parts of the North Pacific, East China Sea, Sea of Japan, and Sea of Okhotsk (Figure 1A). These oceanographic features have allowed the development of many kinds of marine fisheries, and fisheries have traditionally played an important role in food security in Japan (Makino, 2011; Kamoey, 2015). A clockwise mesoscale eddy with Kuroshio water, known as a “Kuroshio Warm Core Ring,” detaches from the Kuroshio Extension, approaches the Pacific coast of Hokkaido, and becomes isolated in Oyashio water (e.g., Itoh and Yasuda, 2010; Figures 1B,C)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
