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ISSN 0859-290X, Vol. 4, No. 4 – June 1999 [Supplement No.5] T he Featherback family, Notopteridae, is one of the most conspicuous groups of fish in the Mekong. The peculiar knife-shaped body with a long anal fin, which is continuous with the caudal fin, readily identifies a featherback. The fish in this family are dusk- and night-active predators, with well-developed teeth on their jaws and tongues. Featherbacks do not have barbels, but they possess a small appendage on each nostril. Other characteristics include a small tuft-like dorsal fin, and very small body scales. Unlike most other fish a featherback does not flex its body when swimming. It swims by means of waving its anal fin, by which it can move both backwards and forwards. The featherbacks are capable of breathing atmospheric air by inflating the swimbladder, and they come to the surface from time to time. The four species of featherbacks in the Mekong basin belong to two genera, Notopterus and Chitala. The only specie belonging to the genus Notopterus is the bronze featherback (Notopterus notopterus). It is relatively small and rarely reaches its maximum size of about 40 cm. In adults the body colour is uniformly silvery grey or bronze, without any markings. One of the main characteristics distinguishing the bronze featherback from the Chitala featherbacks is the slightly curved, regular outline between the head and back. The Chitala species are all "hunchbacked". Another unique trait is that the headscales in the bronze featherback are larger than the body scales; in the Chitala species scales have the same size all over the fish. The bronze featherback can be encountered just about everywhere in the Mekong basin, but it prefers standing or sluggish water. It migrates from the dry season refuges to spawn in rice fields or The Clown featherback (Chitala ornata), a typical representative of the featherback family other floodplain areas during the rainy season. When the floodwaters recede, the fish migrates back to permanent streams and canals. Its favourite food consists of shrimps and aquatic insects. The bronze featherback is caught in traps or with hook and line in rice fields and other small water bodies. Although these fish, like other featherbacks, have more spines in their flesh than any other Mekong fish species, they are popular food fish. Women in markets can be seen skillfully separating the soft meat from skin and bones. Most often the meat is used to make very tasty fish cakes. Soup made from these fish is said to cure measles in children. The second most common specie is the clown featherback (Chifala orna- fa). The adult fish is very easy to recognise. It has a hunchback, the body colouration is greyish with a series of 5-10 large, round, black spots on each side of the flanks (not necessarily the same number on both sides). Each spot is encircled by a well-defined white ring. Juvenile clown featherbacks, however, sometimes have stripes on the tail, and can often be difficult to differentiate from juveniles of the royal featherback (C. blanc/). The clown featherback is a large predatory fish up to 100 cm long. It is found in the Mekong mainstream and in medium to large sized tributaries, where it is often seen, and heard with a big "splash", when it attacks small fish swimming at the surface. It is common also in flood- plain areas where it spawns at the onset of the floods. The eggs are laid on tree stumps or similar solid objects on which they attach. The eggs (and the young fish) are aggressively defended by the male, which will attack any intruder (even humans). The male also ventilates the eggs with its pectoral fins, thereby Mekong Fisheries Network Newsletter preventing suffocation by being covered by sediment. The male is obviously very vulnerable during this period. If a fisher locates a batch of eggs, he will often take advantage of this protecting behaviour and get an easy catch. The female is not known to participate in guarding the eggs. The clown featherback, and the other Chitala are caught with gillnets, cast- nets or hooks baited with shrimps. Gillnets targetting these species are set horizontally, just below the surface, thus taking advantage of the fish's habit of coming to the surface to breathe air. Featherbacks do not constitute an important part of the fish cultured in the Mekong countries, and breeding of clown featherbacks is at the experimental stage. The royal featherback ( Chitala blancl) is endemic to the Mekong basin, but it is less common than the clown featherback. It is only found from northern Cambodia to Thailand and the Lao PDR. The specie lives mainly in rocky areas in the Mekong mainstream and in the largest tributaries. The royal featherback can measure up to about 90 cm in length. The body colours are similar to those of the clown featherback, but the royal featherback has a series of small black spots on the middle of the body, which gradually change into oblique stripes towards the tail. Very little is known about the habits of this specie, but like the previous ones it feeds on fish, crustaceans and aquatic insects. With a length of up to 150 cm the giant featherback is the largest of the four Mekong featherback species, and it is also the rarest -it possibly occurs only in Cambodia. Similar to the bronze featherback, this specie has no markings (the characteristic that is used to separate it from the other Chitala), but the larger size, and the arched humphback profile will normally exclude misidentification. Bronze featherback (Notopterus notopterus), the most common of the featherbacks Royal featherback ( Chitala blanc/), endemic to the Mekong basin Mekong Fisheries Network Newsletter .

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