Key Facts

The Japanese fishing industry provides a critical local food source: per capita consumption of fish and seafood in Japan is nearly three times the world average.³ The Japanese industry also accounted for nearly 5 percent of fish catches globally in 2009.² As the Sea of Japan warms, however, the ecosystems supporting its productive fisheries are changing.^5,18,24,25

• Before 2002, massive outbreaks of the giant jellyfish Nemopilema nomurai occurred about every 40 years.^6,7,8 Since 2002, outbreaks have occurred nearly every year, crippling commercial fisheries.^4,5
• Reef–building corals in the region have rapidly expanded their range northward in response to warming temperatures.¹⁸ At the same time, the coral–eating crown-of-thorns starfish has invaded the region.^24,25
• Given a mid–level scenario for future heat–trapping emissions, temperatures in the Sea of Japan are projected to rise by 5–7° F ( 3–4° C) by the end of the century.^28,29 This warming will likely create more favorable conditions for invasive species.^12,14

Details

The Sea of Japan is home to one of the world's most productive fisheries, accounting for nearly 5 percent of the global fish catch in 2009.² Japan maintains one of the world's largest fishing fleets, and annual per capita fish and seafood consumption in the country is 134 pounds (60.8 kilograms)—more than three times the world average.³

In the past decade, however, Japanese fisheries have suffered from nearly annual blooms of the giant jellyfish Nemopilema nomurai.^4,5 Before 2002, massive outbreaks occurred about every 40 years.^8,6,7 These jellyfish—which can reach two meters in diameter and nearly 441 pounds (200 kilograms)^8,9—cause numerous problems, including clogging and bursting of fishing nets, high mortality of commercial fish species, and a higher risk that fishing boats will capsize.⁴

One of the largest outbreaks of N. nomurai in history occurred in 2005, when 300–500 million jellyfish were transported from the East China Sea through the Tsushima Strait.^4,5,10 During another outbreak in 2009, a 10–ton trawler sank as its crew tried to haul in a net containing dozens of the jellies.¹¹

While the precise cause of the outbreaks is not yet certain, warmer conditions are linked to increases in the size of jellyfish populations.^12,13,14,15 From 1976 to 2000, temperatures in the Yellow Sea— likely spawning ground for N. nomurai jellyfish—rose by 3.1° F (1.7° C).¹⁶ In the Sea of Japan itself, winter sea surface temperatures have increased by 2.9–4.3° F (1.6–2.4° C) over the last century.^17,18 Warming seas may also be exacerbating jellyfish outbreaks already linked to nutrient loading, coastal development, and overfishing.^5,32 For instance, overfishing species that prey on jellyfish removes a critical check on the jellyfish population, creating an opportunity for these strong survivors to multiply.³²

Part of a Larger Pattern

The recent jellyfish outbreaks are part of a larger pattern of changes in marine ecosystems in the Sea of Japan. The region is home to some of the world's highest–latitude coral reefs,¹⁹ and five coral species that are found nowhere else in the world.¹⁸ As ocean temperatures in temperate latitudes rise, corals have the potential to expand their range.^18,20

Since the 1930s, four major categories of tropical coral species have been rapidly expanding northward into more temperate waters.¹⁸ The pace of expansion has been up to 8.7 miles (14 kilometers) per year, which greatly outpaces the average expansion rate for terrestrial species of 2,001 feet (610 meters) per year.^18,21

The northward expansion of these coral species presents several potential problems for native reef ecosystems. Competition between faster–growing tropical species and species native to more temperate waters may cause the latter to decline. And organisms associated with the tropical reefs may also expand their range. For example, reef fish in Australia have been expanding their range poleward in response to rising temperatures,²² as have corals along the Florida peninsula.²³

The coral–eating crown–of–thorns starfish (Acanthaster planci) has already expanded its range into the Sea of Japan,^24,25 causing declines in reef fish²⁵ and affecting tourism throughout the region. The larval stage of this starfish species requires warm (at least 82° F, or 28° C) temperatures, and can survive only within a fairly narrow temperature window.²⁶ These warm conditions are increasingly likely to occur at higher latitudes.

What the Future Holds

The rise in water temperature in the Sea of Japan and associated ecosystem migrations are occurring in the context of a global rise in sea surface temperature of 0.18° F (0.1° C) per decade since 1901.²⁷ Continued burning of oil, gas, and trees—and a mid–level scenario for future heat–trapping emissions—are projected to cause temperatures in the Sea of Japan to rise by another 5–7°F (3–4°C) by the end of this century.^28,29

In response to human-induced warming, the speed of the Kuroshio Current is expected to increase,³⁰ delivering even more heat from the tropics to the region. Warming temperatures are likely to expand the range of tropical jellyfish species, and lead to more jellyfish outbreaks.^12,14

As the world's oceans absorb excess carbon dioxide from the atmosphere and become more acidic, coral growth is inhibited while jellyfish populations expand.³¹ Developing more sustainable coastal development and fishing practices—which are also likely factors in the invasion of jellyfish^5,32 and starfish^33,34 species—can help mitigate these problems.

Credits

Endnotes

1. Photograph: Nomura Jellyfish damage Japanese fishing industry, September 2007. Courtesy of Ryan Formanek. Available online at http://www.flickr.com/photos/13771169@N05/1404414172/in/ gallery-49535267@N06-72157626122815956/. Accessed March 22, 2011. ↑
2. Food and Agriculture Organization of the United Nations. 2009. Online at http://www.fao.org/fishery/statistics/en. ↑
3. Food and Agriculture Organization of the United Nations. No date. FAOSTAT data for 2007. Rome, Italy. Online at http://faostat.fao.org/site/610/DesktopDefault.aspx?PageID=610#ancor. ↑
4. Kawahara, M., S. Uye, K. Ohtsu, and H. Iizumi. 2006. Unusual population explosion of the giant jellyfish Nemopilema nomurai (Scyphozoa: Rhizostomeae) in East Asian waters. Marine Ecology Progress Series 307:161–173. ↑
5. Uye, S. 2008. Blooms of the giant jellyfish Nemopilema nomurai: A threat to the fisheries sustainability of the East Asian Marginal Seas. Plankton & Benthos Research 3(Suppl.):125–131. ↑
6. Shimomura, T. 1959. On the unprecedented flourishing of 'Echizen Kurage' Stomolophus nomurai (Kishinoye), in the Tsushima current regions in autumn,1958. Bulletin of the Japan Sea Regional Fisheries Research Laboratory 7:85–107 (in Japanese with English abstract). ↑
7. Yasuda, T. 2004. On the unusual occurrence of the giant medusa Nemopilema nomurai in Japanese waters. Nippon Suisan Gakkaishi 70:380–386 (in Japanese). ↑
8. Kishinouye, K. 1922. Echizen kurage (Nemopilema nomurai). Dobutsugaku Zasshi 34:343–345 (in Japanese). ↑
9. Omori M., and M. Kitamura. 2004. Taxonomic review of three Japanese species of edible jellyfish (Schyphozoa: Rhizostomeae). Plankton Biology and Ecology 51:36–51. ↑
10. Toyokawa, M., A. Shimizu, K. Sugimoto, K. Nishiuchi, and T. Yasuda. 2010. Seasonal changes in oocyte size and maturity of the giant jellyfish, Nemopilema nomurai. Fisheries Science 76:55–62. ↑
11. Ryall, J. 2009. Japanese fishing trawler sunk by giant jellyfish. Telegraph, November 2. Online at http://www.telegraph.co.uk/earth/6483758/Japanese-fishing-trawler-sunk-by-giant-jellyfish.html. ↑
12. Cushing, D.H. 1989. A difference in structure between ecosystems in strongly stratified waters and in those that are only weakly stratified. Journal of Plankton Research 11:1�13. ↑
13. Purcell, J.E. 2005. Climate effects on formation of jellyfish and ctenophore blooms: A review. Journal of the Marine Biological Association of the United Kingdom 85:461–476. ↑
14. Purcell, J.E., S. Uye, and W–T. Lo. 2007. Anthropogenic causes of jellyfish blooms and their direct consequences for humans: A review. Marine Ecology Progress Series 350:153–174. ↑
15. Gibbons, M.J., and A.J. Richardson. 2008. Patterns of pelagic cnidarian abundance in the North Atlantic. Hydrobiologia 616:51–65. ↑
16. Lin C., J. Ning, J. Su, Y. Lin, and B. Xu. 2005. Environmental changes and the responses of the ecosystem of the Yellow Sea during 1976–2000. Journal of Marine Systems 55:223–234. ↑
17. Takatsuki, Y., et al. 2007. Long–term trends in sea surface temperature adjacent to Japan. Sokko-Jiho 74:S33–S87. ↑
18. Yamano, H., K. Sugihara, and K. Nomura. 2011. Rapid poleward range expansion of tropical reef corals in response to rising sea surface temperatures. Geophysical Research Letters 38:L04601. ↑
19. Yamano, H., K. Hori, M. Yamauchi, O. Yamagawa, and A. Ohmura. 2001. Highest–latitude coral reef at Iki Island, Japan. Coral Reefs 20:9–12. ↑
20. Hoegh-Guldberg O., P.J. Mumby, A.J. Hooten, R.S. Steneck, P. Greenfield, et al. 2007. Coral reefs under rapid climate change and ocean acidification. Science 318(5857):1737–1742. ↑
21. Parmesan, C., and G. Yohe. 2003. A globally coherent fingerprint of climate change impacts across natural systems. Nature 421:37–42. ↑
22. Figueira, W. F., and D. J. Booth. 2010. Increasing ocean temperatures allow tropical fishes to survive overwinter in temperate waters. Global Change Biology 16:506–516. ↑
23. Precht, W. F., and R. B. Aronson. 2004. Climate flickers and range shifts of reef corals. Frontiers in Ecology and the Environment 2:307–314. ↑
24. Yamaguchi, M. 1986. Acanthaster planci infestations of reefs and coral assemblages in Japan: A retrospective analysis of control efforts. Coral Reefs 5(1):23–30. ↑
25. Sano, M, M. Shimizu, and Y. Nose. 1987. Long-term effects of destruction of hermatypic corals by Acanthaster planci infestation on reef fish communities at Iriomote Island, Japan. Marine Ecology Progress Series 37:191–199. ↑
26. Yasuda, N., K. Ogasawara, K. Kajiwara, M. Ueno, K. Oki, H. Taniguchi, S. Kakuma, K. Okaji, and K. Nadaoka. 2010. Latitudinal differentiation in the reproduction patterns of the crown–of–thorns starfish Acanthaster planci through the Ryukyu Island Archipelago. Plankton & Benthos Research 5(4):156–164. ↑
27. Rayner, N.A., P. Brohan, D.E. Parker, C.K. Folland, J.J. Kennedy, M. Vanicek, T.J. Ansell, and S.F.B. Tett. 2006. Improved analyses of changes and uncertainties in sea surface temperature measured in situ since the mid-nineteenth century: The HadSST2 dataset. Journal of Climate 19:446–469. ↑
28. Kolstad, E.W., and T.J. Bracegirdle. 2008. Marine cold–air outbreaks in the future: An assessment of IPCC AR4 model results for the Northern Hemisphere. Climate Dynamics 30:871–885. ↑
29. The scenario referred to here is the mid–level emissions scenario known as A1B from the Intergovernmental Panel on Climate Change. ↑
30. Sakamoto, T.T., H. Hasumi, M. Ishii, S. Emori, T. Suzuki, T. Nishimura, and A. Sumi. 2005. Responses of the Kuroshio and the Kuroshio Extension to global warming in a high–resolution climate model. Geophysical Research Letters 32:L14617. ↑
31. Attrill M.J., J. Wright, and M. Edwards. 2007. Climate–related increases in jellyfish frequency suggest a more gelatinous future for the North Sea. Limnology and Oceanography 52:480–85. ↑
32. Richardson, A.J., A. Bakun, G.C. Hays, and M.J. Gibbons. 2009. The jellyfish joyride: Causes, consequences and management responses to a more gelatinous future. Trends in Ecology and Evolution 24(6):312–322. ↑
33. Birkeland C. 1982. Terrestrial run–off as a cause of outbreaks of Acanthaster planci (Echinodermata: Asteroidea). Marine Biology 69:175–185. ↑
34. Brodie J., K. Fabricius, G. De'ath, and K. Okaji. 2005. Are increased nutrient inputs responsible for more outbreaks of crown-of-thorns starfish? An appraisal of the evidence. Marine Pollution Bulletin 51:266–278. ↑