Hemibagrus spilopterus
Etymology
Hemibagrus: from the Greek hemi, meaning ‘half’ and the generic name Bagrus.
spilopterus: from the Greek spilos, meaning ‘spot’, and pteryx, meaning ‘fin’, in reference to the black spot on the adipose-fin.
Classification
Order: Siluriformes Family: Bagridae
Distribution
This species has been recorded from the middle-to-lower Mekong system in Laos, Vietnam, Cambodia and Thailand plus the Dong Nai (Vietnam), Ban Pakong, Chao Phraya and Mae Khlong (Thailand).
Type locality is ‘Bassac River at village of Prek Chey on Vietnamese border, 10°57’N, 105°06’E, Kandal, Cambodia’.
Habitat
Inhabits slowly-flowing or standing waters including main river channels and lakes, with riverine populations typically performing localised migration into flooded forest during the wet season, returning to the main river channels in November and December.
Maximum Standard Length
The largest officially-recorded specimen measured 500 mm.
Aquarium SizeTop ↑
Suitable only for public displays or the very largest home aquaria.
Maintenance
Likely to prefer dim lighting and access to refuges in the form of driftwood, large rocks or lengths of plastic piping.
An enormous filtration system and dedicated regime of water changes should also be considered mandatory.
Water Conditions
Temperature: 20 – 27 °C
pH: 6.0 – 8.0
Hardness: 36 – 357 ppm
Diet
This species is a predator feeding primarily on crustaceans and smaller fishes, although there should be no need to use such live foods in captivity.
Smaller specimens will readily accept live or frozen bloodworm, Tubifex and most dried foods whereas adults can be offered earthworms, prawns/shrimp, mussels, strips of white fish flesh and larger sinking pellets.
Juveniles require a relatively high-protein diet whereas adults should not require feeding on a daily basis with 1-2 meals per week sufficient.
This species should never be fed the meat of mammals such as beef heart or chicken since some of the lipids and other organic compounds contained in these meats cannot be properly metabolised by fishes, causing excess fat deposition and even organ degeneration over the long term.
Behaviour and CompatibilityTop ↑
Aggressively territorial and incompatible with other fishes in all but the largest public installations and even then may attack its tankmates.
It’s also one of few freshwater fishes that appear unafraid of humans meaning care must be exercised when performing maintenance.
Sexual Dimorphism
Males possess an elongate genital papilla.
Reproduction
Unrecorded.
NotesTop ↑
This species is relatively common in the ornamental trade but has been widely misidentified as the congener H. nemurus which is native to Java and may never have been exported for aquaria.
Given its eventual size, aggressive nature and the fact it can live for several decades it shouldn’t be considered a home aquarium subject in all but the most exceptional circumstances.
Hemibagrus has been divided into a number of putative species groups which may or may not represent monophyletic assemblages, and following a major review by Ng and Kottelat (2013) H. spilopterus is included in the H. nemurus group.
Members of this assemblage can be told apart from other congeners by possession of 43–46 vertebrae, a relatively short adipose-fin base measuring less than 20% SL, a uniform colour pattern with no black markings on the lateral line and usually a greyish caudal-fin in life.
Currently valid species are H. capitulum, H. filamentus, H. fortis, H. hoevenii, H. nemurus, and H. spilopterus.
H. spilopterus can be told apart from all other group members by possession of a gently-curved (vs. flat) interorbital space.
In addition it differs from H. capitulum in having a shorter dorsal-fin (adpressed fin excluding the filamentous extensions of the fin rays if present not reaching adipose-fin origin vs. reaching to or beyond), from H. filamentus in having a larger dorsal to adipose distance (10.8–17.6 % SL vs. 7.7–10.9) and from H. fortis in that the anterior branch of each dorsal-fin ray is longer than the other branches giving the fin an overall jagged appearance (vs. branches of the dorsal-fin rays of almost equal length giving a rounded appearance), plus the adipose-fin is shorter and deeper(maximum height 1.7–3.2 times in the length of its base vs. 2.8–4.9).
It can be further distinguished from H. hoevenii in that the premaxillary tooth band is not exposed when the mouth is closed (vs. partially exposed) plus possession of rounded (vs. tapering) caudal-fin lobes, absence (vs. presence) of a thick dark margin around the caudal-fin, a rounded (vs. triangular) anal-fin, broader dorsal-fin membranes giving the fin a rounded (vs. triangular) appearance and filamentous extensions on the dorsal-fin that do not reach beyond the middle of the adipose-fin base (vs. filamentous extensions of the first two dorsal-fin rays that reach beyond the posterior of the adipose-fin base).
It differs from H. nemurus in having a larger eye in specimens larger than around 150 mm SL (eye diameter 12–18 % HL vs. 9–11).
The genus Hemibagrus currently contains 40 nominal species which are distributed east of the Godavari River system in India and south of the Changjiang (Yangtze) drainage in China, with Southeast Asia a particular centre of diversity.
Many species are important food fishes and some are cultured for the purpose, or for sport angling.
Hemibagrus has previously been considered synonymous with Mystus but following Ng and Kottelat (2013) members can be diagnosed by their moderate to large adult size and strongly-depressed head shape with the interorbital region normally flat or slighly convex.
The grouping also shares a number of characters with the genera Sperata and Bagrus, and these three can be separated from other bagrids by the following: mesethmoid highly depressed (vs. not highly depressed), prominent (vs. reduced) dorsoposterior laminar extension of the mesethmoid, the first infraorbital with (vs. lacking) a posterolateral spine, enlarged (vs. moderate or small) premaxilla, and the metapterygoid with a long, free posterior margin (vs. contacting quadrate and hyomandibular).
Hemibagrus can be told apart from Sperata by possession of a a relatively short and slender (vs. enlarged and elongate) interneural and by absence (vs. presence) of a concave surface in the posterior portion of the posttemporal in which lies a portion of the swimbladder.
It’s distinguished from Bagrus by possession of 7, very rarely 8 (vs. 8-10) soft dorsal-fin rays.
References
- Ng, H. H. and W. J. Rainboth, 1999 - The Raffles Bulletin of Zoology 47(2): 555-576
The bagrid catfish genus Hemibagrus (Teleostei: Siluriformes) in central Indochina with a new species from the Mekong River. - Ferraris, C. J., Jr., 2007 - Zootaxa 1418: 1-628
Checklist of catfishes, recent and fossil (Osteichthyes: Siluriformes), and catalogue of siluriform primary types. - Ng, H. H. and M. Kottelat, 2005 - The Raffles Bulletin of Zoology 61(1): 205-291
Revision of the Asian catfish genus Hemibagrus Bleeker, 1862 (Teleostei: Siluriformes: Bagridae).
