DistributionRead full entry
Anguilla bicolor has diverged between the Indian and Pacific Oceans giving rise to two subpopulations (Ege 1939). The population found in the Indian Ocean (sometimes referred to as A. bicolor bicolor in the literature) is genetically homogeneous in this ocean, but significantly different from the Pacific Ocean clade (referred to as A. bicolor pacifica) (Minegishi et al. 2012). There is also continued debate about whether the Indian Ocean subpopulation might also be considered as two separate management units (K. Tsukamoto, 2014 pers. comm.).
The Pacific population is native to the coasts of China, Taiwan, Vietnam (Hue province, Quang Ngai city, Phu My (Binh Dinh province), Ba river (Gia Lai, Dac Lac, Phu Yen provinces)), Philippines and the islands of Borneo, Sulawesi Island, New Guinea, and the Marianas. In a study by Sugeha and Suharti (2008), conducted around the Indonesian Archipelago, it was found from the western Sulawesi Island to the western Papua Island whilst the Indian Ocean population was found from the western Sumatera Island to the southern Jawa Island (Sugeha and Suharti 2008).
The Indian Ocean subpopulation is distributed from the east coast of Africa, the Arabian Peninsula (Oman and Yemen, including Socotra, in coastal drainages of the Gulf of Oman, Arabian Sea, and Gulf of Aden (EPAA 2002)), it is widespread in the tropical Indian Ocean (Seychelles, Madagascar and Mascarenes), east to India, Sri Lanka, Bangladesh, Myanmar. It is found across to northwestern Australia (known only from streams in the Kimberley regions of northwestern Western Australia and Kakadu National Park in the Northern Territory (Allen et al. 2002, Larson and Williams, in prep.)), and greater Sundaland. Recent studies suggest that it is even more widespread also occupying the western and northern parts of the Malaysian Peninsula (Arai et al. 2012). In Africa, it is widespread but relatively uncommon along the east and southeast African coast from South Africa to Tanzania and Madagascar, including the Lower Shire River System of the Lower Zambezi in Malawi (Tweddle and Willoughby 1979) and Tana River (Copley 1958). In southern Africa it occurs in the eastern part of the region, only present in lower coastal plain sections. In Zimbabwe it is only known from the Save-Runde confluence. It may be present in eastward flowing rivers of east Africa, although it has not been recorded from Kenyan rivers (Seegers et al. 2003). There is a known locality in Somalia, which also suggests the subspecies is present the entire length of the African east coast.
Anguilla bicolor is thought to have potentially three spawning grounds, two of which are in the Indian Ocean (North-East of Madagascar and South-West Sumatra) with speculation of another somewhere in the Pacific (Robinet and Feunteun 2002, Robinet et al. 2003). As a result of the two Indian Ocean spawning sites, it has further been proposed that this subpopulation, may itself be further divided into Eastern and Western units due to oceanographic processes (the South Equatorial Current of this ocean bifurcate into to two gyres, which easily separates the population into two), and while research is required to establish this, it could be potentially be important with regard to conservation and management (K. Tsukamoto, pers. comm.).