Clarias sp.

Freyhof, JÖrg, Yoğurtçuoğlu, Baran, Jouladeh-Roudbar, Arash & Kaya, Cüneyt, 2025, Handbook of Freshwater Fishes of West Asia, De Gruyter : 594-595

Clarias sp.

Common name. Walking catfish.

Diagnosis. Distinguished from C. gariepinus by: ● body stout, its depth strongly increasing to vertical of pelvic origin, then decreasing / ● anterior margin of pectoral spine rugose and with irregular bumps / ● posterior dorsal tip reaching to or beyond caudal base / ● flank brown or grey, often with vertical series of yellowish spots. Size up to 450 mm SL and 1.2 kg, usually about 250 mm SL.

Distribution. Hot springs in upper Sakarya. Native to Philippines and introduced in tropical areas worldwide.

Habitat. Lowland habitats such as marshes, ponds, lakes, rice fields, and rivers, often in relatively small lowland and hill streams. Most commonly found in stagnant, muddy water, but also in clear springs and lakes.

Biology. In native range, matures at about 280 mm SL and spawns during rainy season when rivers rise. An accessory respiratory organ allows this species to breathe air. Dependent on atmospheric oxygen and will drown if cut off from surface. Usually makes lateral migrations into flooded forests and fields during wet season to feed and spawn. Can use its strong pectoral spines to leave water and move to new areas through very shallow channels. Mating position

Clarias sp. , Nha Trang, Vietnam, ~ 200 mm SL.

in a form of amplexus is maintained for several seconds. In amplexus, male lies in a U-shaped curve around female’s head. Sperm and eggs are released, followed by a vigorous flick of female’s tail to disperse eggs over a wide area. Pairs mate several times during a spawning night. Males excavate nests in submerged mud banks but do not guard eggs or larvae. Eggs adhere to vegetation. Nocturnal bottom feeders on invertebrates and fish, occasionally on plants. An important commercial species in Southeast Asia and for aquaculture in warm-water and tropical countries, introduced almost worldwide.

Conservation status. Non-native; released from aquaria or aquaculture.

Remarks. This species is usually identified as C. batrachus , which is known only from Java in Indonesia. Records of C. batrachus from mainland Southeast Asia, Sundaic Southeast Asia, and the large pantropical non-native range suggest two other species are involved in what is called C. batrachus . Non-native populations need to be better identified, and it cannot be excluded that they represent undescribed species or hybrids between different species.

Further reading. Ng & Kottelat 2008 (identification); Emiroğlu et al. 2020 (upper Sakarya).

Heteropneustes fossilis ; Greater Zab; Iraq; 87 mm SL.