Hemibagrus wyckii

Hemibagrus: from the Greek hemi, meaning 'half' and the generic name Bagrus.

This species has an enormous distribution and occurs throughout much of central Indochina and western Indonesia.

Records exist from the Mekong and Chao Phraya drainages in Laos, Vietnam, Cambodia and Thailand, the Pahang River drainage in Peninsular Malaysia, Batang Hari and Musi River drainages in Sumatra, the Citarum drainage in Java, and the Baram, Rejang, Kapuas and Barito systems in Borneo.

Type locality is given as 'Java in flumine Tjitarum, provinciae Preanger, prope vicum Parongkalong', which translates as Java, Tjitarum (Citarum) river, Preanger province, near Parongkalong village.

Most commonly collected in middle reaches of moderate to large-sized rivers where it sometimes occurs in rapids and other turbulent habitats.

It also performs localised migration into flooded forest during the wet season from July to October.

Suitable only for public displays or the very largest home aquaria.

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.

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.

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.

Unrecorded.

Juvenile specimens are sometimes available in the aquarium trade although their purchase is strongly discouraged, and given its eventual size, aggressive nature and the fact it can live for several decades this species shouldn't be considered a home aquarium subject in all but the most exceptional circumstances.

Despite the common name the blue-coloured eye is not given as a distinguishing character in any diagnosis we've seen.

H. wyckii can be told apart from most other congeners by the diagnostic characters given in Ng and Kottelat (2013) for the H. wyckii species group (see below) and from other group members by possessing a strongly-ossified dorsal spine which is at least as thick as the branched dorsal-fin rays (vs. poorly ossified spine thinner than the soft dorsal-fin rays) with 10–12 (vs. no) serrations on the posterior edge, a cream-coloured (vs. grey or olive green) cleithral region, cream-coloured (vs. orange, red or grey) principal rays in both the upper and lower caudal-fin lobes and a shorter maxillary barbel (reaching to the middle of the dorsal-fin base; 144–195% HL vs. reaching to at least the middle of the adipose-fin base; 230–301% HL).

It also has a grey caudal-fin which further distinguishes it from H. maydelli and H. wyckioides since both have reddish to orange caudal fins.

Desoutter (1975) noted Indochinese specimens possessed fewer pectoral fin-rays (10–11 vs. 11–12) and more vertebrae (45 vs. 41–44) than the Javanese type material but this was considered intraspecific variation by Ng and Rainboth (1999)[3].

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. wyckii is included in the H. wyckii group.

Members of this assemblage can be told apart from other congeners by possession of a broad, highly-depressed head, 50-54 vertebrae and light-coloured principal rays in both upper and lower caudal-fin lobes.

Currently valid members are H. maydelli, H. microphthalmus, H. wyckii, and H. wyckioides.

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.