Оңтүстік-Шығыс Азиядағы Омбай бұғазы

Strait in Southeast Asia

Ombai Strait (, Estreito de Ombai, ) is an international strait in Southeast Asia. It separates the Alor Archipelago from the islands of Wetar, Atauro, and Timor in the Lesser Sunda Islands. The strait is also the western portion of a pair of international straits, the other one being Wetar Strait; the two straits combine to link the Pacific Ocean with the Indian Ocean.

Ombai is an alternative name for the island of Alor, in the Alor Archipelago on the other side of the strait's north, north western and western coastline. In Tetum, the expression tasi feto is often used to refer to the 'Ombai Wetar Strait', which extends along most of Timor's northern shores. The counterpart of that body of water, the Timor Sea, which has larger waves, is more turbid, and washes the whole of Timor's southern coastline, is commonly referred to in Tetum as tasi mane .

Ombai Strait is relatively narrow and deep It has complex and extreme bathymetry, ranging from narrow reef flats (often less than wide) partly covered with seagrass and coral, to depths within of the coast. The Alor Archipelago, and the western part of Timor except the coastal exclave of Oecusse, which is on the north coast of western Timor, are part of the province of East Nusa Tenggara, Indonesia. Wetar is part of the Maluku Province of Indonesia. Atauro, Oecusse, and the eastern part of Timor comprise the nation of East Timor. Beyond the end of the channel at the strait's north eastern extremity, between the islands of Alor and Atauro, is the Flores Sea to the north west and north, and the Banda Sea to the north east. That channel is wide at its narrowest point, where the navigable waters are across. As such, Ombai Strait is one of two deep water passages in the Indonesian archipelago that link the waters of the Pacific and Indian Oceans, the other one being Wetar Strait. The archipelago is the only interocean connection on earth at low latitudes, and the exchange of water between the two oceans is known as the Indonesian Throughflow (ITF). By this and other ITF pathways, nutrient rich water from the Pacific Ocean runs into the Indian Ocean, at a rate 50 times faster than the discharge of the Amazon River. The ITF currents are at their weakest during the north east monsoon rainy season (December–February), when there are also strong westerly (onshore) winds and waves. Seagrass beds protect coral reefs from sedimentation and are feeding grounds for dugong (Dugong dugon), an endangered species. Seven genera of seagrass are known to exist off East Timor's coastline as a whole. A survey of Tibar Bay carried out in 2016 found three mangrove species, namely Sonneratia alba, which was the dominant species, Avicennia marina and Rhizophora stylosa. The report of another survey, carried out in 2017, stated that the dominant species in the area was Sonneratia albia, and that there were some clusters of Rhizophora apiculata, Ceriops tagal, and Lumnitzera. East Timor, on the south side of the two straits, is a recognized global hotspot for whales and dolphins. Ombai Strait in particular has been identified as a critical habitat for sperm whales (Physeter macrocephalus), blue whales (Balaenoptera musculus), giant oceanic manta rays (Manta birostris) and sea turtles (Cheloniidae), amongst other endangered, threatened and protected species. Other species that have been observed consistently in the strait include false killer whales (Pseudorca crassidens), and spinner dolphins (Stenella longirostris), both of them in huge pods made up of large numbers of individuals. The report of a 2013 survey of Tibar Bay, on Ombai Strait's southern shore not far west of Dili, East Timor, noted that a local dive tourism operator had made frequent sightings of dugong along the coast immediately east of the bay, and that there were also anecdotal reports of saltwater crocodiles in the bay. Ombai Strait is also part of the Coral Triangle, which is recognised as a global centre of marine biodiversity. The coastal zones of East Timor have important areas of coral reef ecosystems, such as the ones at Tasitolu and in the Bay of Dili. At Tasitolu, the reefs west of Dili Rock are live, healthy and diverse, but those to the east of the rock have lower coverage and more reef rubble. At the Port of Dili inside the Bay of Dili, there are at least four different species of coral. and Atauro (East Timor). The southern edge of the strait is also the northern shore of four East Timorese IBAs. From west to east, they are Be Malae (just to the west of the Loes River), Maubara (a short distance east of the village of Maubara), Tasitolu (just to the west of Dili), and Areia Branca no Dolok Oan (on the eastern side of the Bay of Dili).

The village of Lamalera (pop. 2,500) on the south coast of Lembata, facing the south western entrance to the strait, is known for its hunting of sperm whale and other deep sea species. The hunting has been taking place for at least six centuries, and is allowed under International Whaling Commission regulations concerning aboriginal whaling. However, conservationists worry that commercial whaling also takes place, and that hunters use their engine powered boats all year round to catch other protected species such as manta rays, orcas (Orcinus orca), dolphins and oceanic sharks.

On World Oceans Day 2020, the Ombai Wetar Strait was designated as a Mission Blue Hope Spot. The designation recognises the importance of conserving the open waters on the north side of East Timor, with their globally significant coral reefs and marine biodiversity. It also emphasises the potential of the two straits for sustainable marine ecotourism development.

Under the United Nations Convention on the Law of the Sea, a commercial vessel or aircraft has freedom of navigation or overflight solely for the purpose of continuous and expeditious transit of a strait between one part of the high seas or exclusive economic zone and another. That transit passage principle applies to Ombai Strait and Wetar Strait, as they combine to link two oceans. The Ombai Wetar route is longer in distance than its Strait of Malacca Singapore Strait counterpart. The former route is therefore not really a preferred alternative path for west to east commercial traffic. If there were any disruption in the flow of commercial shipping on the Malacca Singapore route, the Ombai Wetar route would also have a crucial role to play in global trade, especially for the Asia Pacific region. The channels of the Ombai Wetar route are extremely deep. In 1977, a paper published by the International Institute for Strategic Studies, based in London, ranked the Ombai Wetar route as the second most important strait in the world to U. S. defense interests, after the Strait of Gibraltar. The two straits are now also considered by China to be strategically significant. A 2021 study concluded that a number of species of sardines (and also other small pelagic fish) were caught on the north coast of East Timor, with flat bodied sardinellas (S. gibbosa etc.) being the dominant species group landed at Loes, and relatively abundant at Comoro. At most sites, catches of these pelagic species varied moderately between years, and were larger during the rainy season and when medium sized turbid plumes were extending from river mouths. Fishers at various sites generally perceived a decline in landings over the previous 20 years. They attributed the decline to several human factors, including higher fishing effort, plastic pollution, motorisation of canoes and larger scale, less selective fishing gear. Some sardine species were sold readily to traders; others were commonly kept for immediate home consumption. According to another 2021 study, the exploitation rate of flying fish in Ombai Strait is relatively low, and at a rational and sustainable utilisation range. The cetaceans migrating along the route are often very close to shore; Atauro's west coast dive sites, located within the strait, are said to be the best way to experience the island's diving. There are other dive sites in the strait, near Dili including Tasitolu, but Alor's main diving areas are not within the strait.