Hemibagrus nemurus (Valenciennes, 1840)

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 : 231-234

Hemibagrus nemurus (Valenciennes, 1840)

( Fig. 21 )

Bagrus nemurus Valenciennes , in Cuvier & Valenciennes, 1840: 423 (type locality: Java); Bleeker, 1846a: 155; 1846b: 285; 1847: 6; 1849: 10; 1851a: 260, 261; 1851d: 416, 420; 1855a: 469; 1855d: 393, 394; 1857b: 476, 477; 1858a: 418; 1858b: 48; 1858e: 150 (in part); 1859c: 357; 1859g: 134 (in part).

Bagrus Sieboldii Bleeker, 1846a: 27 (type locality: Batavia [= Jakarta], Java); 1846b: 285.

Hemibagrus nemurus - Bleeker, 1862: 55, Pl. 69 (in part); Ferraris, 2007: 90 (in part).

Macrones nemurus - Günther, 1864: 80 (in part); Weber, 1894: 420 (in part); Weber & de Beaufort, 1913: 341 (in part).

Mystus (Mystus) nemurus - Jayaram, 1966: 446 (in part).

Mystus nemurus - Roberts, 1993: 28, Fig. 63; Kottelat et al., 1993: 66 (in part; not pl. 31).

Hemibagrus cf. nemurus - Rachmatika, 2003: 57, Pl. 28.

Material examined. — JAVA: ZRC 40144, 1 ex., 53.2 mm SL , Jawa Barat: Kecamatan Cijeruk, Desa Pamoyanan, Cipinang Gading at Kampung Sawah , Bera ; ZRC 42564, 5 ex., 192.6–323.0 mm SL, ZRC 41504, 1 ex., 255.7 mm SL , Jawa Barat: Sungai Sokan at Cibalagung, a probable outlet of Cirata Reservoir at Citarum , 6°47'58"S 107°16'21"E; ZRC 43855, 1 ex., 88.5 mm SL , Jawa Barat: Cisadane near Leuwiliang , 6°35’7”S 106°37’57”E; ZRC 44087, 1 ex., 420 mm SL , Jawa Barat: market in Banjar , 7°22'S 108°32'E; ZRC 43911, 3 ex., 26.2–66.0 mm SL , Jawa Tengah: Kali Progo about 15 km W to Yogyakarta, next to Moyudan , 7°47'59"S 110°14'46"E; ZMA 121.818 , 2 ex., 85.2–89.0 mm SL , Jawa Tengah: Opak River at Kampung Kritek ; ZRC 40554, 6 ex., 339–390 mm SL , Jawa Timur.

Diagnosis. — Hemibagrus nemurus differs from H. capitulum in having a smaller eye in specimens larger than approx. 150 mm SL (9–11% HL vs. 11–19), the adpressed dorsal fin (excluding the filamentous extensions of the fin rays if present) not reaching to (vs. reaching to or beyond) the origin of the adipose fin, and shorter maxillary barbels (reaching to origin of anal fin vs. beyond caudal-fin base but frequently to vertical through base of last anal-fin ray; 168–221% HL vs. 193–390), from H. filamentus in having a relatively shorter and wider head (head width 60–70% HL vs. 55–60) and longer dorsal to adipose distance (10.2–16.2% SL vs. 7.7–10.9). It is distinguished from H. fortis in having the anteriormost branch of each dorsal-fin ray longer than other branches (vs. branches of almost equal length) giving the dorsal fin a jagged (vs. rounded) distal margin ( Fig. 20 ), a shorter, deeper adipose fin (maximum height of adipose fin 1.9–3.2 times in the length of its base vs. 2.8–4.9) and a smaller eye (9–15% HL vs. 16–29), from H. hoevenii in having the premaxillary tooth band not (vs. partially) exposed when the mouth is closed, rounded (vs. tapering) caudal-fin lobes, absence (vs. presence) of a broad and conspicuous dark margin around the caudal fin, a rounded (vs. triangular) anal fin, broader membranes of the dorsal fin which give it a rounded (vs. triangular) appearance, and lacking filamentous extensions on the dorsal fin (vs. very long filamentous extensions of the first two dorsal-fin rays that reach beyond the posterior base of the adipose fin), and from H. spilopterus in having a flat (vs. gently convex) interorbital space, and smaller eye (9–11% HL vs. 12–18 in specimens larger than approx. 150 mm SL; 13–15% HL vs. 15–18 in specimens smaller than approx. 150 mm SL).

Description. — Biometric and meristic data as in Table 11. General description as for genus. Head depressed and broad, body moderately compressed; head width 60–70% HL. Interorbital space flat. Eye diameter 9–15% HL. Premaxillary tooth band not exposed when mouth is closed. 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. Adipose-fin base short, approximately as long as anal-fin base; maximum height 4.9–7.4% SL (1.9–3.2 times in length of adipose-fin base). Adipose-fin origin separated from base of last dorsal-fin ray by distance of 10.2–16.2% SL. Dorsal spine stout, with 10–12 serrations on posterior edge. Anteriormost branch of each dorsal-fin ray longer than other branches, imparting jagged distal margin to fin; no conspicuous filamentous extensions present on fin rays; membranes broad, imparting rounded appearance. Adpressed dorsal fin not reaching adipose fin. Pectoral spine stout, with 20–28 large serrations on posterior edge. Anal fin rounded, origin slightly posterior to adipose origin. Caudal fin forked; upper and lower lobes rounded. Maxillary barbels reaching to origin of anal fin (168–221% HL). Maximum recorded size 380 mm SL.

Colour. — Dorsal surface of head and body uniform brownish-grey; ventral surface of head and body dirty white; adipose fin brownish-grey, without black spot; fin-rays and inter-radial membranes of all fins grey; dorsal surface of barbels brownish-grey, ventral surface dirty white.

Distribution. — Hemibagrus nemurus is known only from Java ( Fig. 22 ).

Habitat and biology. — Hemibagrus nemurus is primarily an inhabitant of large rivers, and has been described as an opportunistic predator that feeds on fish and aquatic and terrestrial invertebrates ( Rachmatika, 2003).

Remarks. — Hemibagrus nemurus was thought to be widely distributed throughout Sundaic and mainland Southeast Asia. Our examination of a large series of material from throughout Southeast Asia revealed consistent differences in morphology and morphometrics in material initially thought to be conspecific. These led to the recognition of five other species: H. capitulum from Borneo, Sumatra and the Malay Peninsula (this is the species identified as H. nemurus in most works on Sundaic Asian fishes and distinguished from it by its larger eye in specimens greater than approx. 150 mm SL and the adpressed dorsal fin reaching to or beyond the origin of the adipose fin when depressed), H. filamentus from the middle and lower Mekong River drainage in Indochina (distinguished from H. nemurus by its longer, narrower head), H. fortis from central Borneo (distinguished from H. nemurus by its rounded dorsal fin, lower adipose fin and smaller eye), and H. spilopterus from the drainages throughout Indochina (distinguished from H. nemurus in having a flat interorbital space and larger eye in specimens greater than approx. 150 mm SL). In a previous study, Tan & Ng (2000) had identified Sumatran populations of H. nemurus as distinct from the Javanese population, and had tentatively considered them conspecific with the Bornean H. fortis . Further investigations here have revealed that the Sumatran populations are referable to H. capitulum , and are not conspecific with H. fortis .

Valenciennes (in Cuvier & Valenciennes, 1840) described Bagrus nemurus from a single specimen of 15 Parisian inches (= 406 mm) TL collected by Kuhl and van Hasselt in Java. The holotype is believed to be deposited in the RMNH in Leiden ( Roberts, 1993a), but some of the Javanese material collected by Kuhl and van Hasselt is also deposited in the MNHN in Paris. A search of these two collections by the first author failed to find any Javanese material of H. nemurus collected by Kuhl & van Hasselt, save for a skeleton in the RMNH (RMNH 269) bearing the unpublished name “ Bagrus tetragonocephalus van Hasselt ”. This skeleton is too small to be the holotype (being only 175 mm SL). Although the holotype of Bagrus nemurus could not be located, there is little ambiguity about the identity of this species (since only one species of Hemibagrus with 43–46 vertebrae is known from Java), and a neotype designation would not fulfill the conditions of Article 75 of the International Code of Zoological Nomenclature. We also note that a previous attempt to stabilise the taxonomy of the species was rejected (Ng et al., 1999: Case 3061; International Commission for Zoological Nomenclature, 2002: Opinion 2011), and concur that there is no compelling argument for the designation of a neotype.

Hemibagrus nemurus differs from both H. capitulum and H. spilopterus in having a smaller eye in specimens larger than approx. 150 mm SL (9–11% HL vs. 11–19 and 12–18 respectively). In specimens smaller than approx. 150 mm SL, there is broad overlap in eye size between H. nemurus and H. capitulum (diameter 13–15% HL vs. 12–19 respectively), but the eye of H. nemurus is still smaller than that of H. spilopterus at this size (diameter 13–15% HL vs. 15–18 respectively).

The synonymy of Bagrus sieboldii with H. nemurus follows that of Bleeker (1858e) and Roberts (1989). There is no indication from available data that indicates otherwise (Ng et al., 1999), and we retain the synonymy of the two nominal species here.

Figures

Fig. 21. Hemibagrus nemurus, ZRC 42564, 238.6 mm SL, Java: Sungai Sokan.

Fig. 20. Schematic illustrations of fully extended dorsal fins of members of the H. nemurus species group: a, H. fortis, ZRC 40522, 126.9 mm SL; b, other members of the H. nemurus species group (H. nemurus, ZRC 39181, 132.4 mm SL, illustrated). Scale bar = 10 mm.

Fig.22. Map showing collection localities of Hemibagrus nemurus, H. capitulum and H. filamentus specimens examined in this study.