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Text and photos by Nick Baker, unless credited to others.
Copyright ゥ Ecology Asia 2024



Asian Swamp Eel

Fig 1

Fig 2

Fig 3

Fig 4










Order : Synbranchiformes
Species : Monopterus javanensis
Maximum Length : 100 cm

Monopterus javanensis (Asian Swamp Eel) occurs in a range of aquatic habitats including rivers, lakes, ponds, rice paddies, marshes, swamps and urban drains. It is tolerant of  polluted water or low oxygen levels, and can breathe air efficiently enough to allow migration across short distances of dry land. They are mainly nocturnal, emerging to feed on fishes, crustaceans and other invertebrates.

Though swamp eels appear similar in shape to true eels they are in fact unrelated: swamp eels lack scales, have greatly reduced fins, and have a single v-shaped gill-opening beneath the throat rather than twin lateral gill-openings as in other fishes.  

The Asian Swamp Eel is rounded in cross-section, has  a distinctive blunt snout and a tapered tail. Its colour is variable, but is generally greenish-grey or brown speckled with pale-coloured spots or flecks.

Their eggs are laid in bubble-nests in shallow water. Fry and juveniles are all female, but with the onset of adulthood some females will develop into males.

This edible species occurs in India, China and Japan and throughout Southeast Asia.  

Fig 1 : 30 cm example in an urban drain in Ipoh, Perak, Peninsular Malaysia. 

Fig 2 : 50 cm example in a boggy stream at Clementi Woodlands, Singapore.

Fig 3 : This low-lying, swampy area harbours many Asian Swamp Eel, Singapore.

Fig 4 : Close-up of a 70 cm example in an open-country, concretised drain, Singapore.

References : F1