With many factors at play, the picture is complicated. At a physical level, the IPCC report points out that increasing sea-surface temperatures in the tropical and temperate regions of oceans are likely to drive the larger, cooler water, commercial fish towards the poles. “So we may see more warm-water fish,” notes Takayanagi. The flows of ocean currents may also change. Japan is affected by two major currents that are important to fish production: the warm Kuroshio Current flows up the eastern side of the country and the cold Oyashio Current to the north of Hokkaido.up the eastern side of the country and the cold Oyashio Current to the north of Hokkaido.