Kuroshio Current large marine ecosystem

Source: NOAA

Introduction

The Kuroshio Current Large Marine Ecosystem (LME) extends from the Philippines to the Japanese archipelago. The Kuroshio (Black Current) is a warm (average sea surface temperature, 24°C) current flowing in a northeasterly direction along Japan’s east coast. It is about 100 kilometers (km) wide, and it has an average speed of 3 to 4 knots. The Tsushima Current branches off towards the Sea of Japan. The LME’s huge latitudinal expanse provides it with a rich variety of marine habitats. The region has a generally mild, temperate climate. The underwater topography includes the Japan Trench, the Shatsky Rise, the Ryukyu Trench and the Okinawa Trough. Natural hazards in this region are active volcanoes, numerous seismic occurrences, tsunamis and typhoons. LME book chapter and articles pertaining to this LME include Terazaki, 1989.

Productivity

caption Location of the Kuroshio Current Sea Large Marine Ecosystem. (Source: NOAA)

For a map of currents in the seas around the Japanese archipelago, including in this LME, see Terazaki, 1989, p. 38. For more information on the physical and chemical characteristics of the Kuroshio Current ecosystem, see Terazaki, 1989. Eddy-like motions have been observed in the coastal regions of the Kuroshio Front, which separates the Kuroshio Current from the East China Sea LME. There are indications that these eddies contribute to the retention and subsequent survival of sardine larvae transported by the Kuroshio Current. The Kuroshio Current LME is considered a Class II, moderately high (150-300 gC/m2-yr) productivity ecosystem based on SeaWiFS global primary productivity estimates. Coastal areas are highly productive. The maximum value of chlorophyll is found at a depth of around 100 meters (see Ichimura, 1965). The annual biomass of plankton fluctuates from year to year. It is usually most abundant in the eddy area of the Kuroshio’s edge. In the outer area, plankton distribution is low. For more information on bacteria biomass, phytoplankton biomass, and zooplankton biomass, see Terazaki, 1989. The spring zooplankton biomass is much greater than in winter (see Kozasa, 1985). The LME is an important spawning and nursery ground for many important pelagic fishes such as clupeoids, horse mackerel, scomber and saury. GLOBEC and JGOFS are involved in studies of the ocean environment in relation to biological production in the Kuroshio/Oyashio transitional region. Seasonal variations in temperature and nutrients were measured in Sagami Bay in the northern section of this LME (see Terazaki, 1989). In the southern part of this LME, the Ryukyu Archipelago has a tropical environment characterized by coral reefs, mangrove swamps and many diverse marine organisms.

Fish and Fisheries

caption (Source: NOAA)

Species harvested in this LME include the Japanese sardine, Pacific saury, anchovy, jack mackerel, horse mackerel, frigate mackerel, yellowtail, filefish, herring, sea robin, and parrot bass. For information on the fluctuation of pelagic fish, and particularly the sardine catch, see Terazaki, 1989. The sardine population reached an all time maximum in the 1930’s, then decreased, from 1964 to 1971. It has since increased. These fluctuations have been accompanied by geographic shifts in spawning and nursery grounds. For more information on the decline of the Pacific sardine, see the article on the web by Oozeki. For a map of distribution of Pacific saury larvae, see Terazai, 1989, p. 59. Between 1955 and 1975, there were observed fluctuations in catch for yellowtail, horse mackerel, filefish, parrot bass and sea robin, in Sagami Bay. Japan is a major fishing nation with a focus on the conservation and management of its marine living resources. Ishigaki Island Station in the Ryukyu Islands at the southern end of the Japanese archipelago is developing methods to monitor the marine environment and to conserve fishing grounds. The University of British Columbia Fisheries Center has detailed fish catch statistics for this LME. Click on the graph below for more information.

Pollution and Ecosystem Health

Japan's rapid economic development after World War II impacted its marine environment. Rivers have been polluted. On the Pacific side there is air pollution from power plant emissions, resulting in acid rain. Lakes and reservoirs are under acidification, resulting in a decrease in water quality and a threat to aquatic life. Japan is one of the world’s largest consumers of fish and contributes to the depletion of fisheries in Asia and elsewhere. In this LME however, overfishing is not considered the top area of concern. Nor do aquaculture and the harvesting of marine pharmaceutical plants and animals rank among the most serious pollution problems in this LME. In the 1960s, heavy industries concentrating along the Japanese coast caused severe water pollution. There were resulting red tides. Strict laws and standards established in the 1970s have improved the quality of coastal waters, although eutrophication in areas such as Tokyo Bay is still serious despite the development of sewage systems. In the Tokyo/Yokosuka area, sewage pollution, habitat destruction and non-biodegradable pollution are considered the most serious problems. Further north, in the Hakodate/Otsuchi area, non-biodegradable pollution is seen as the most serious problem followed by sewage pollution and oil pollution. The numbers of reported marine pollution incidents for the coastal areas of Japan appear high. There have been oil spills and incidents caused by land-based sources. Striped dolphins are heavily and indiscriminately harvested in Japanese coastal waters. A marine environmental monitoring plan for coastal Japan is under discussion.

Socio-economic Conditions

caption (Source: NOAA)

The latitudinal extension of this LME accounts for the regional variations in culture and economic development. The Japanese archipelago comprises 4 main islands and 200 smaller islands, including those of the Amami, Okinawa, and Sakishima chains of the Ryukyu Islands. The fisheries sector is a major economic activity in Japan. Japan relies on the sea for its supply of fish, seaweed and other marine resources. Japan maintains one of the world's largest fishing fleets and accounts for nearly 15% of the global catch. Gray whales were traditionally hunted by Japanese fishermen off the eastern shore of Honshu. Modern commercial whaling continued until the 1960s. Information is available on Japanese whaling. An efficient transport system links the islands. Because of a lack of natural resources, food, fuel, and raw materials for industry have to be imported in large quantities. Japan is very dependent on trade and international shipping. The main Pacific ports are Hachinohe, Shimizu, Tokyo, and Tomakomai.

Governance

Japan and Taiwan are involved in the governance of this LME. As a country with major interests in fishery, Japan has formulated and implemented conservation and management measures. In 1971, it established an Environment Agency. In 1988, it passed a law regulating the manufacture and use of chlorofluorocarbons (CFCs) which damage the ozone layer. Since 1975, Japan’s Environment Agency has been conducting an annual survey of marine pollution in seas adjacent to Japan including this LME. Another marine research program, initiated in 1995, evaluates the effects of pollution on marine organisms and of air pollution on the marine environment. Internationally, Japan plays a central role. The gray whale, which Japan has fished, is legally protected under the International Convention for the Regulation of Whaling. The International Whaling Commission (IWC) has urged Japan to stop harvesting striped dolphins. In 2001, Japan defied the IWC by hunting Dall’s porpoise in its seas. Japan is party to the following conventions: the Antarctic-Environmental Protocol, Antarctic-Marine Living Resources, Antarctic Seals, Antarctic Treaty, Biodiversity, Climate Change, Desertification, Endangered Species, Environmental Modification, Hazardous Wastes, Law of the Sea, Marine Dumping, Nuclear Test Ban, Ozone Layer Protection, Ship Pollution, Tropical Timber 83, Tropical Timber 94, Wetlands, and Whaling.

References

Articles and LME Volumes

  • Terazaki, Makoto, 1989. "Recent Large-Scale Changes in the Biomass of the Kuroshio Current Ecosystem" in Kenneth Sherman and Lewis M. Alexander (eds.), Biomass Yields and Geography of Large Marine Ecosystems (Boulder: Westview) AAAS Selected Symposium 111, pp.37-65. ISBN: 0813378443.

Other References

  • Asami, T. 1983. Estimation of standing stock and production of fish eggs and larvae in the East China Sea. Kuroshio Exploitation and Utilization Research Program Rep. 6:257-272.
  • Ichimura, S. 1965. A short review on primary production in the Kuroshio. Inform. Bull. Planktol. Jap. 12:1-6.
  • Kozasa, E. 1985. Distribution and composition of zooplankton. Kuroshio Exploitation and Utilization Research Program Rep. 8:240-247.
  • Kurogane, K., 1977. Statistical consideration on the composition of fish species of the set-net catch in Sagami Bay. Bull. Tokai Reg. Fish. Res. Lab. 89:1-16.
  • Odate, K. and Kotani, Y., 1985. Possible role of the Kuroshio Current in determining distribution of saury in the Northwestern Pacific. In The Kuroshio IV. Proceedings of the Fourth CSK Symposium. 1979. Ed. By A.Y. Takenouchi. Saikon Publishing Co., Tokyo.
  • Saiki, M. 1982. Relation between the geostrophic flux of the Kuroshio in the Eastern China Sea and its large meander in the south of Japan. Oceanogr. Mag. 32:11-18.
  • Oozeki, Y., “Mechanism causing the variability of the Japanese sardine population”.
  • Sawara, T., 1974. One the sea surface temperature in the East China Sea for the years, 1953-1972. Oceanogr. Mag. 26:17-36.
  • Sigurdson, J., 1995. Science and Technology in Japan. Britain: Cartermill International Limited. ISBN: 1860670121.



Disclaimer: This article is taken wholly from, or contains information that was originally published by, the National Oceanic and Atmospheric Administration (NOAA). Topic editors and authors for the Encyclopedia of Earth may have edited its content or added new information. The use of information from the National Oceanic and Atmospheric Administration (NOAA) should not be construed as support for or endorsement by that organization for any new information added by EoE personnel, or for any editing of the original content.

Glossary

Citation

(2008). Kuroshio Current large marine ecosystem. Retrieved from http://www.eoearth.org/view/article/51cbee4b7896bb431f696c1c

0 Comments

To add a comment, please Log In.