Airsac catfish (Heteropneustes microps)
|Size||Length: 15 cm (2)|
The airsac catfish is classified as Vulnerable (VU) on the IUCN Red List (1).
The peculiar looking airsac catfish (Heteropneustes microps), 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).
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).
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).
The little-known airsac catfish is an omnivore that feeds during the night. It forms loose schools of about ten individuals (2).
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.
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.
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- Brackish: slightly salty water.
- Endemic: a species or taxonomic group that is only found in one particular country or geographic area.
- Omnivore: an organism that feeds on both plants and animals.
- Pectoral fin: in fish, a pectoral fin is found on each side of the body just behind the gills. They are generally used for balancing and braking.
IUCN Red List (June, 2007)
- Pethiyagoda, R. (1991) Freshwater Fishes of Sri Lanka. The Wildlife Trust of Sri Lanka, Colombo.
- Pethiyagoda, R. (1994) Threats to the indigenous freshwater fishes of Sri Lanka and remarks on their conservation. Hydrobiologia, 285: 189 - 201.
- Nelson, J.S. (1994) Fishes of the World. Third edition. John Wiley and Sons, Inc., New York.
- Allaby, M. (1991) The Concise Oxford Dictionary of Zoology. Oxford University Press, Oxford.