The demersal fish resource survey carried out from 1st July - 24th September 1998, off the coast of Sarawak discovered a new abundance fish group the Monacanthidae (Leatherjacket or filefish).  The survey, using the 150 GRT Research Vessel, KK Manchong, used the bottom trawl net with cod-end mesh size of 38 mm and a mean head rope opening of 19.0 metres.
Monacanthidae was the most abundant group in the survey area where the overall mean catch rate was 21.75 kg/hr or 16.0 %.  However, the fish was distributed mainly in water depth of more than 90 metres. This area is close to the edge of the continental shelf where water depth ranges from 90 to 200 metres.  In Substrata 2.3 and 3.3 of the survey, Monacanthidae was found in extreme abundance.  The mean catch rate ranged from 243.73 kg/hr to 437.30 kg/hr. The percentage composition of this group  ranged from 66% to 82%.  There were 8 stations, where the catch rate ranged from 800 kg/hr to 2,975 kg/hr and the density was ranged from 13.63 to 21.01 tonnes/sq nm. This was three times more than the overall mean density of 4.93 tonnes/sq.nm recorded for the whole survey area.
Monacanthidae is called locally as barat-barat.  The fish is normally small, with a strongly compressed body.  The mouth is small with outer row of 6 strong teeth and usually an inner row of 4 teeth in upper jaw.  The gill opening is represented by a small slit above or before the pectoral fin base.  The head and body are covered with minute connected scales with one or more fine spinules which make the skin feel rough and leathery.  The skin is thick.  There are two well separated dorsal fins: the first has two spines with the first spine very well developed. The second soft dorsal fin and anal fin are about equal and opposite.  There is no ventral fin.  The pelvic fin is united and rudimentary. The caudal fin is usually rounded, whereas the pectoral fin is short. 
The fish is omnivorous feeding mainly on variety of benthic organisms such as sponges, corals, hydroids, algae, small worms, crustacean and mollusc. Although edible, some species are said to be bitter and poisonous.  Regionally, the species is distributed from Japan to South China Sea.
There were 8 genera and 12 species recorded in the present survey.  The species were Thamnaconus hypargyreus, Thamnaconus tessellatus, Thamnaconus sp.1, Aluterus monoceros, Aluterus scriptus, Anacanthus barbatus, Cantherhines sp., Monacnathus chinensis, Monacanthus sp., Paramonacanthus sp., Pseudomonacanthus peronii and Pseudolutarius nasicornis.
The most abundant species was Thamnaconus hypargyreus  which dominated the catch in Substrata 2.3 and 3.3. The fish was small with a mean size of 10.3 cm and ranging from 5.5 to 13.5 cm.  Body weight ranged from 10 to 20 gm.
The other species were not found in abundance but distributed throughout the survey area. There were several large species such as Alutera monoceros, Aluterus scriptus, Thamnaconus tesselatus and Cantherhines sp.  Their recorded total length ranged from 23 cm to 50 cm.  The largest specimen belonged to Aluterus scriptus (TL=50cm) and Alutera monoceras (TL=48 cm).
One of the main problems in the exploitation of this fish resource is the economic value.  The fish is small and considered as trash fish with no commercial value locally.  However, because of the huge biomass, there is great potential for commercial exploitation for fishmeal and even for food fish.