Heteropneustes microps (Günther 1864)

The little-known airsac catfish is an omnivore that feeds during the night. It forms loose schools of about ten individuals (2).

There are no known conservation measures currently in place for the Vulnerable airsac catfish. It has been stated that overall, the native fish of Sri Lanka receive no protection whatsoever, and that there is so little monitoring, drastic declines in fish populations could go unnoticed. It has been recommended that the conservation strategy most likely to succeed for the freshwater fish of Sri Lanka is the maintenance of captive populations. These could then be reintroduced once the threats to the wild populations had been controlled (3). It has yet to be seen whether such actions will be taken.

The peculiar looking airsac catfish, known from only a few specimens (3), is an air-breathing, freshwater fish. A long air sac that extends back from the gill chamber acts like a lung and enables the catfish to breathe air (4). It has a long body that narrows to a pointed head, and four pairs of barbels (fleshy projections) protrude from around the mouth. The airsac catfish has a short fin on its back, a long fin on the rear underside of the body, and a rounded tail fin. Despite their tiny size, airsac catfish are dreaded by local fisherman due to the sharp poisonous spine in each pectoral fin that can inflict a painful sting on any person wading in its territory (4) (5).

The airsac catfish has been found in an area heavily modified by man (3), where it inhabits swamps and similar still, often turbid waters, such as irrigation ditches (2). It inhabits both fresh and brackish waters (2). South-western Sri Lanka, where the airsac catfish has been found, is known as the 'wet zone' because it has an additional monsoon to the rest of the country (3).

Thought to be endemic to Sri Lanka (2), the airsac catfish is known from only a few specimens collected in the south-west of the country (3).

Classified as Vulnerable (VU) on the IUCN Red List 2007 (1).

Agriculture in Sri Lanka, such as tea, vegetable and tobacco cultivation, is often heavily dependent on fertilisers. The chemicals used in agriculture are washed by rains into the surrounding waterways and are impacting the habitat of the airsac catfish (3). The restricted distribution of the airsac catfish makes it particularly vulnerable to the effects of any threats such as pollution, as every individual in the population may be rapidly affected.

Eggs of about 2 mm diameter are laid in lumps in a gravel nest. The parents guard the eggs and the youngs.

Occurs mainly in swamps and similar still, often turbid waters (e.g. irrigation ditches). Forms loose schools of about ten individuals of approximately the same size. Enters brackish water. Can survive temperatures up to 39.8°C (Ref. 7256). An omnivore with nocturnal feeding habits. Very easily maintained in captivity. Sympatric with H. fossilis which is more abundant in the type locality. Best method of catch is dewatering of small water holes during drought period.

Adults occur mainly in swamps and similar still, often turbid waters (e.g. irrigation ditches). Form loose schools of about ten individuals of approximately the same size. Enter brackish water. Can survive temperatures up to 39.8°C (Ref. 7256). An omnivore with nocturnal feeding habits. Oviparous, distinct pairing possibly like other members of the same family (Ref. 205). Very easily maintained in captivity. Sympatric with H. fossilis which is more abundant in the type locality. Best method of catch is dewatering of small water holes during drought period.

fisheries: commercial; aquarium: commercial

Heteropneustes microps is a species of airsac catfish possibly endemic to Sri Lanka, though records from India have been made. This species grows to a total length of 15.0 cm (5.9 in). This fish is a component of local commercial fisheries, and is found in the aquarium trade.