Anguilla bengalensis

Common name. Mottled Eel

Diagnosis. Distinguished from A. bicolor by: ● dorsal origin at about midway between pectoral base and anus, clearly in front of anus / ● mottled colour pattern in individuals longer than 300 mm in TL. Size usually about 800 mm, rarely up to 2000 mm total length.

Distribution. In Arabian Peninsula in Wadi Haj and Wadi Masila in Yemen. Also, in rivers on east coast of Africa, from Pongola in South Africa to Genale in south-west Ethiopia. In Asia and Indian Ocean from Pakistan east to Aceh in Indonesia and peninsular Malaysia. Known to occur on oceanic islands, including Madagascar, Mauritius, Reunion, and others. Unknown if there is one or more spawning grounds in Indian Ocean.

Habitat. Mostly found in lowland and coastal areas, but many individuals migrate far upstream. Most abundant inland eel in India. Juveniles found in habitats with coarse gravel and rocks, often in fast-flowing waters.

Biology. Catadromous. Adults reach maturity at 5.5–10.5 years and die after spawning. A seaward spawning migration in April and September (Malaysia) suggests a very long spawning season of at least 6 months. Very few leptocephali of this species have been found. Juveniles feed on insects and other aquatic invertebrates, while adults feed on fish and crabs. Considered to be an “unspoiled rare ornamental species of Himalayan drainage,” often kept in temple ponds for religious purposes in India.

Conservation status. NT; although there is little information on population trends, it is believed that range and abundance are declining worldwide due to dam construction. It is also used as a food source, but despite its wide distribution, there is very little species-specific information on its use and trade, as it is usually lumped together with other eels in catch statistics. Overfishing is a major concern. In some parts of India, it contains levels of contaminants that prove toxic to humans.

Remarks. Often, two subspecies are distinguished: Anguilla b. bengalensis in Indian Ocean and Anguilla b. labiata in Eastern Africa and the Arabian Peninsula. Both subspecies are treated here as conspecific, but further research is needed.

Further reading. Talwar & Jhingran 1992 (biology, identification); Attaala & Rubaia 2005 (Record from Yemen); Crook & Nakamura 2013 (trade); Jacoby et al. 2015 (threats, conservation); Shiraishi & Crook 2015 (trade); Arai & Abdul Kadir 2017a (distribution, habitats); Arai & Arai Kadir 2017b (spawning); Chai & Arai 2018 (age at maturation); Pike et al. 2020b (biology, distribution, conservation status).