Arafura Sea

• Category: Marine and Oceanic Biomes.
• Geographic Location: Pacific Ocean.
• Summary: This shallow tropical sea, located in the southwestern Pacific Ocean between Australia and New Guinea, has been threatened by overfishing.

Situated between the Timor and Coral Seas in the southwestern Pacific Ocean, the Arafura Sea is a shallow tropical, semi-enclosed, continental-shelf basin spanning 251,000 square miles (650,087 square kilometers) in the East Indian archipelago. The name Arafura is derived from the inhabitants of the Maluku Islands of Indonesia, known as Alforas or Haraforas to 19th-century English anthropologists.

Straddling the Indian Ocean–Australian continental shelves, the Arafura overlays a section of the Sahul Shelf known as the Arafura Shelf, part of a prehistoric land bridge that once connected present-day Australia and New Guinea and was key to the intercontinental migration of humans from Asia into Australia.

The Arafura is bordered by the eastern islands of Indonesia, the Ceram and Banda Seas to the northwest, the southern coast of New Guinea to the north and northeast, the Torres Strait to the east, the Gulf of Carpentaria to the southeast, the northern coast of Australia to the south, and the Timor Sea to the west. It is approximately 800 miles (1,287 kilometers) long and 350 miles (563 kilometers) wide, with depths of 165 to 265 feet (50 to 81 meters) increasing to the west, with depths up to 2,000 feet (610 meters) along its western edge. For most of the year, the Arafura Sea experiences stable trade winds, with monsoons appearing during the summer months.

Marking the boundary between the Indian and Pacific Oceans, the Arafura Sea is an important part of the thermohaline circulation, the global heat conveyor belt that is critical to the regulation of the Earth's climate. During the southeast Asian summer monsoon system, a four-month period of extensive convective thunderstorms, the warm waters of the Arafura are pulled westward into the Indian Ocean by the South Equatorial Current. During the Indian winter, conversely, the Equatorial Counter Current reverses the flow, thus known as the Indonesian Throughflow.

Marine Biodiversity

Along with the neighboring Timor Sea, the Arafura Sea is considered to be one of the last remaining areas of tropical marine biodiversity in the Southeast Asia–Australia region, with an estimated 840 to 1,000 species, including corals, marine worms, crustaceans, echinoderms, mollusks, pelagic fish, demersal fish, and benthic fish. Biologically speaking. However, the Arafura remains relatively unknown, with the majority of the studies being done concerning its commercial fisheries.

The first biological survey of the Arafura's benthic fauna—the animals that live on or near the seabed—was conducted by the Australian Museum in 2005 and revealed several taxa new to science, including the polychaete families Hartmaniellidae and Longosomatidae.

Threats from Overfishing

The rich marine life of the Arafura has been threatened by overfishing and unreported and illegal fishing. Between 1992 and 2000, the number of shrimp trawlers operating in the Arafura doubled, while the number of fish trawlers more than tripled. The sustainable shrimp catch limit for the Arafura has been estimated at 21,700 tons (19,686 metric tons) per year. By 2000, however, that limit had already been exceeded, even without taking into account illegal fishing. Overfishing pearls, which are harvested in the clear, protected waters surrounding the Aru Islands in the north, has also been reported. A study conducted between 1999 and 2003 found that the Arafura Sea red snapper stock was undergoing a collapse. Additionally, increased pressure on shark fisheries has created unsustainable practices. The Ministry of Marine Affairs and Fisheries of Indonesia found that the production of aggregated sharks in the Arafura Sea in 2020 and 2021 was above 4,000 tons for both years. Studies have shown that sharks recover from population declines slowly due to long reproductive periods and low fecundity. As such, uncontrolled fishing can easily lead to a rapid decline in populations.  

In recent years, conservationists have called for tighter fishing regulations and even a fishing moratorium in the Arafura Sea's Exclusive Economic Zones to allow the depleted fish stocks to recuperate. The Arafura Sea and Timor Sea Expert Forum was established to promote the sustainable development of this region and protect not only the area's rich biodiversity but also the livelihoods of the local communities that depend on a healthy ecosystem. One of these communities is the Asmat, a group of some 70,000 indigenous people known for head-hunting and wood carving who live along the narrow, muddy rivers that flow into the Arafura Sea on the southern coast of New Guinea. The Asmat use dugout canoes and large hoop nets to catch fish and shrimp. Since 2020, Yayasan Konservasi Alam Nusantara (YKAN) has partnered with the United Nations Development Program (UNDP) for the Arafura to work with the Timor Sea Expert Forum to manage fisheries in the Arafura Sea and implement action plans that support available fish stocks without overfishing.

Hydrocarbon Deposits and Oil Production

Geologically, the Arafura Sea is bordered by the Australian craton to the south, the Tertiary collision zone to the south, the Banda arc collision zone to the west and northwest, and the western limit of late Paleozoic granites to the east. The sediment of the Arafura is rich in calcium carbonate and ranges from 540 million to 65 million years, covering the late Paleozoic, Mesozoic, and Cenozoic eras. The seabed of the Arafura has been the focus of energy exploration in the form of hydrocarbons such as oil and natural gas.

Crude oil and natural gas were first discovered here in 2000 by the Abadi-1 exploratory well, operated by the Tokyo-based oil company INPEX. In 2010, the Indonesian government approved a development plan to produce 2.5 million tons a year in the Abadi gas field. In 2011, the Indonesian government awarded the British energy company BP two energy-production-sharing contracts covering more than 6,000 square miles (15,540 square kilometers) of the Arafura Sea.

Bibliography

Earl, George Windsor, et al. Sailing Directions for the Arafura Sea. Hydrographic Office, 1837.

Institute of Southeast Asian Studies. Working With Nature Against Poverty: Development, Resources and the Environment in Eastern Indonesia. Australian National University, 2009.

International Hydrographic Organization. Limits of Oceans and Seas. 3rd ed., International Hydrographic Organization, 1953.

Kasim, Kamaluddin, et al. "Toward Sustainable Fishing Practices in Indonesia: Defining a Catch Quota Allocation for Saddletail Snapper (Lutjanus Malabaricus) in the Arafura Sea." Coastal Management, vol. 52, no. 3, May 2024, pp. 97-111. EBSCOhost, doi.org/10.1080/08920753.2024.2370061. Accessed 28 Oct. 2024.

Katili, John A. Future Petroleum Provinces of the World: Geology and Hydrocarbon Potential of the Arafura Sea. American Association of Petroleum Geologists, 1986.

Nurdin, Erfind, et al. "Stock Assessment and Management Strategies for Shark Fisheries in the Arafura Sea: A Length-Based Analysis of Carcharhinus Sealei." Egyptian Journal of Aquatic Research, vol. 49, no. 2, 2023, doi.org/10.1016/j.ejar.2023.02.001. Accessed 28 Oct. 2024.

Rockefeller, Michael. The Asmat of New Guinea. New York Graphic Society, 1967.

Wilson, George D. F. Arafura Sea Biological Survey: Draft Report on Benthic Fauna Collected During RV Southern Surveyor Voyage 05-2005. Australian Museum, 2010.