The Angalarri, Scortum neili Allen, Larson, and Midgley (Teleostei: Terapontidae): description of adults and their habitat

Abstract

Fourteen mature specimens of the Angalarri grunter (Scortum neili Allen, Larson and Midgley) were collected from the main headwater tributary of the Angalarri River in the Victoria River system, Northern Territory, seventeen years after its original discovery at this site in 1981. The distinctive habitat features of this stretch of river include deep (5-6 m), wide (> I 0 m) pools with closed dense canopy, submerged and exposed fringing tree roots, and an algal-covered substrate mostly comprising pebbles to very large rocks and rock ledges with crevices. Scorttllll neili were common and appear to be confined to this panicular river stretch where they were seen in schools of up to twenty-five individuals, often in association with other fishes including Jenkins' grunter (Hephaestus jenkinsi). Remains of algae and other vegetation in stomachs together with the size and shape of the gut suggests that this species is primarily a herbivore/ detritivore. Counts of fin rays, scales and gill rakers were consistent with the type material except that up to 24 transverse scales below the lateral line were counted on the specimens collected from this survey, compared with a maximum count of 21 in the holotype and paratype specimens. Differences in several proportional measurements between the specimens collected in this survey and the relatively smaller paratypes could be accounted for by ontogenetic growth.