Brunei Bay - Fauna

Fauna

Howes and Sahat (in prep) collected 79 species of fishes belonging to at least 34 families in mangrove areas within Brunei Estuary. About half of these species were of some importance in the Brunei markets. The most commonly encountered species, using a variety of sampling techniques, were catfish (Aniidae), Caranx spp., Sardinella spp., Drepane punctata, Coilia dussumieri, Liza vaigiensis, Mugil sp, Plotosus anguillaris, Scatophagus argus. Scomberomorus guttatus and Siganus spp. The intertidal mudflats and sandflats provide foraging areas for a number of migratory shorebirds. Censuses at seven sites in October and November 1986 produced a total of 633 shorebirds of 17 species (Howes & Sahat, in prep). The commonest species were Pluvialis dominica, Charadrius mongolus, Numenius phaeopus, Tringa lotanus, Xenus cinereus, Actitis hypoleucos and Heteroscelus brevipes. Species typical of muddy substrates, such as Limnodromus semipalmatus, Calidris tenuirostris and C. ruficollis, were very scarce. Other waterfowl recorded during the survey included 39 Egretta sacra, small numbers of Butorides striatus, Egretta garzetta, E. alba, Ardea sumatrana and Leptoptilos javanicus, and over 360 terns of seven species, mainly Chlidonias hybrida, C. leucoptera, Sterna dougallii and S. albifrons. The rare and possibly endangered Chinese Egret (Egretta eulophotes) appears to be a regular winter visitor to Brunei Bay in small numbers. Howes and Sahat observed 12 during their survey of the Brunei Estuary in October/November 1986, and reported a maximum of 13 in the nearby Sarawak portion of the bay in May 1986.

The mangrove forests support significant populations of the Proboscis Monkey (Nasalis larvatus) and leaf monkeys (Presbytis sp), as well as large colonies of flying foxes (Pieropus vampyrus). Eleven species of prawns have been recorded in the bay. Three of these, Penaeus merguiensis, P. indicus and Metapenaeus brevicornis, are of high commercial importance, and two others are of minor commercial importance.

Preliminary studies suggest that the intertidal flats support a rather poor zoo-benthos compared with that at many other sites in Southeast Asia. In a recent study, five major taxonomic groups were found from eight sampling sites. Crustacea (Natantia) were the most abundant group, followed by Polychaeta, Bivalvia, Pisces and Gastropoda. Natantia (prawns) were more abundant in the outer estuary, whilst Polychaeta dominated in the mangrove channels near Bandar Seri Begawan sewage outflow (Sahat, 1987; Howes & Sahat, in prep). The poor zoo-benthos may be attributable to the high acidity of the water draining into the bay from the peat swamp forests behind the mangroves.