Hemibagrus sabanus

Ng, Heok Hee & Kottelat, Maurice, 2013, Revision Of The Asian Catfish Genus Hemibagrus Bleeker, 1862 (Teleostei: Siluriformes: Bagridae), Raffles Bulletin of Zoology 61 (1), pp. 205-291 : 214

Hemibagrus sabanus (Inger & Chin, 1959)

( Fig. 4 )

Mystus sabanus Inger & Chin, 1959: 294 (type locality: Borneo: Sabah, Kinabatangan River at Deramakot); 1962: 137; Jayaram & Sanyal, 2003: 104, Fig. 24 .

Mystus (Mystus) sabanus – Jayaram, 1966: 446.

Hemibagrus sabanus – Mo, 1991: 132; Lim & Wong, 1994: 53; Martin-Smith & Tan, 1998: 589; Ferraris, 2007: 91.

Material examined. — BORNEO: Sabah: FMNH 68088 , holotype, 118.5 mm SL ; FMNH 68061 , 1 paratype, 97.5 mm SL ; FMNH 68062 , 5 paratypes, 47.7–93.3 mm SL ; FMNH 68085 , 1 paratype, 151.6 mm SL ; FMNH 68086 , 1 paratype, 130.7 mm SL ; FMNH 68087 , 1 paratype, 94.8 mm SL ; BMNH 1958.4 .28.5, 1 paratype, 122.2 mm SL, Kinabatangan District , Kinabatangan River at Deramakot camp ; ZRC 41190, 1 ex., 93.2 mm SL, Sungai Kinabatangan at Sukau ; ZRC 42743, 6 ex., 105.0– 142.6 mm SL, Sandakan , Sungai Kinabatangan at Pekan Bukit Garam ; ZRC 40493, 1 ex., 104.9 mm SL, lower Segama river at Bukit Belacong ; ZRC 42741, 6 ex., 93.2–110.5 mm SL, Sungai Segama , small village on road to Sungai Kinabatangan .

species group), with the fin having a lunate appearance, whereas in all other members of this species group, they are much broader, allowing the fin to be spread wider and imparting a more rounded appearance to the fin.

Description. — Biometric and meristic data as in Table 2. General description as for genus. Head depressed and broad, body moderately compressed. Dorsal profile rising evenly but not steeply from tip of snout to origin of dorsal fin, then sloping gently ventrally from there to end of caudal peduncle. Ventral profile horizontal to origin of anal fin, then sloping dorsally to end of caudal peduncle. Caudal-peduncle depth 7.4–9.0% SL. Adipose-fin base moderately long, about 2.0–2.5 times anal-fin base (8.9–34.3% SL); distance from origin to base of last dorsal-fin ray 1.2–4.4% SL. Dorsal spine stout, with 6–9 serrations on posterior edge.Adpressed dorsal fin reaching adipose fin; membranes between rays narrow; second ray extended, imparting lunate appearance to fin. Pectoral spine stout, with 15–19 large serrations on posterior edge. Anal-fin origin slightly posterior to adipose origin; distal margin straight. Caudal fin forked; upper lobe tapering with uppermost principal ray produced into filament, lower lobe rounded posteriorly. Outer mandibular-barbel length 127.5–162.1% HL. Maximum recorded size 153 mm SL.

Colour. — Dorsal surface of head and body uniform light grey to grey (live or freshly-dead specimens with yellowish hue, fading in preserved specimens), lateral line cream to yellow; ventral surface of head and body dirty white; adipose fin and fin rays of all fins grey; inter-radial membranes of all fins dirty yellow.

Distribution. — Hemibagrus sabanus is known from the Kalabakan, Kinabatangan and Segama river drainages in northern Borneo ( Fig. 5 ).

Diagnosis. — Hemibagrus sabanus differs from all other members of the H. baramensis species group in having a larger adipose fin located nearer the dorsal fin (length of adipose-fin base 8.9–34.3% SL vs. 19.3–26.3; dorsal to adipose distance 1.2–4.4% SL vs. 4.7–10.6), a more slender caudal peduncle (depth 7.2–9.4% SL vs. 8.7–11.4), and (except for H. semotus ) the upper lobe of the caudal fin regularly tapering (vs. rounded posteriorly). The dorsal fin of H. sabanus also has a narrower appearance. The membranes between the rays in H. sabanus are narrower with an extended second dorsal-fin ray (absent in all other members of this Habitat and biology. — Unlike other members of the species group, H. sabanus is restricted to large rivers (at lower elevation). The diet consists largely of arthropods, both aquatic and terrestrial (Inger & Chin, 1962).

Figures

Fig. 4. Hemibagrus sabanus, ZRC 40493, 104.9 mm SL, Borneo: Sabah, Segama River.

Fig. 24. Hemibagrus filamentus, CMK 13393, 110.2 mm SL, Laos: Nam San.

Fig. 5. Map showing collection localities of Hemibagrus sabanus and H. semotus specimens examined in this study.