Walking catfish

The walking catfish has an elongated body shape and reaches almost 0.5 m (1.6 ft) in length and 1.2 kg (2.6 lb) in weight.[3] Often covered laterally in small white spots, the body is mainly coloured a gray or grayish brown.[5] This catfish has long-based dorsal and anal fins,[5] as well as several pairs of sensory barbels. The skin is scaleless, but covered with mucus, which protects the fish when it is out of water.

This fish needs to be handled carefully when fishing it due to its embedded sting or thorn-like defensive mechanism hidden behind its fins (including the middle ones before the tail fin, similar to the majority of all catfishes).

These fish for sale in HAL market, Bangalore, India are not likely to be C. batrachus (see confused species in text)

The walking catfish is a tropical species native to Southeast Asia. The native range of true Clarias batrachus is confirmed from the Indonesian island of Java only, but three closely related and more widespread species frequently have been confused with this species. These are C. magur of northeast India and Bangladesh, a likely undescribed species from Indochina, and another likely undescribed species from the Thai-Malay Peninsula, Sumatra, and Borneo.[3][4] Both of these undescribed species have been referred to as, Clarias aff. batrachus.[3] At present, the taxonomic position of the Philippines population (called hito or simply "catfish" by the locals) is unclear, and it also is unclear whether South Indian populations are C. magur or another species.[4] As a consequence, much information (behavioral, ecological, related to introduced populations, etc.) listed for C. batrachus, may be for the closely related species that have been confused with true C. batrachus.[4] True C. batrachus, C. magur and the two likely undescribed species are all kept in aquaculture.[4]

Walking catfish thrive in stagnant, frequently hypoxic waters,[5] and often are found in muddy ponds, canals, ditches, and similar habitats. The species spends most of its time on, or right above, the bottom, with occasional trips to the surface to gulp air.[5]

In the wild, this creature is omnivorous; it feeds on smaller fish, molluscs, and other invertebrates, as well as detritus and aquatic weeds. It is a voracious eater that consumes food supplies rapidly, so it is considered harmful when invasive.[6]

Within Asia, this species has been introduced widely.[3] It has also been introduced outside its native range where it is considered an invasive species. It consumes the food supplies of native fish and preys on their young. It also is regarded as an invasive species because they can destroy fish farms.

Clarias batrachus, captured by a juvenile Double-crested Cormorant, Phalacrocorax auritus, at the Anhinga Trail in Everglades National Park, Florida, United States

In the United States, it is established in Florida.[7] It is reported in California, Connecticut, Georgia, Massachusetts, and Nevada. The walking catfish was imported to Florida, reportedly from Thailand, in the early 1960s for the aquaculture trade.[5] The first introductions apparently occurred in the mid-1960s when adult fish imported as brood stock escaped, either from a fish farm in northeastern Broward County or from a truck transporting brood fish between Dade and Broward Counties. Additional introductions in Florida, supposedly purposeful releases, were made by fish farmers in the Tampa Bay area, Hillsborough County in late 1967 or early 1968, after the state banned the importation and possession of walking catfish.

Aquarium releases likely are responsible for introductions in other states. Dill and Cordone (1997) reported this species has been sold by tropical fish dealers in California for some time. They also have been spotted occasionally in the Midwest.

In Florida, walking catfish are known to have invaded aquaculture farms, entering ponds where they prey on agricultural fish stocks. In response, fish farmers have had to erect fences to protect ponds. Authorities have also created laws that ban possession of walking catfish.

In 2017, Clarias were recovered from the River Tonge, near Bolton, Northern England.[8]

In Thailand, this fish is known as, pla duk dan (Thai: ปลาดุกด้าน). It is a common, inexpensive food item, prepared in a variety of ways. It often is offered by street vendors, especially grilled or fried.[9]

This fish is one of the most common freshwater catfish in the Philippines where it is known as hito in the local language.

In Indonesia, it is called lele, and it is the main ingredient in several native dishes, such as pecel lele.

It is a delicacy in the Indian state of Assam, where it is called magur mas (মাগুৰ মাছ).

It is eaten in West Bengal মাগুর মাছের ঝোল and is considered good during illness, particularly weakness in body. It is prepared in a light curry sauce with coriander powder and cinnamon powder. It reportedly is fed to children to develop body strength.

In Karnataka, it is called murgodu (ಮುರ‍್ಗೋಡು).[10] In coastal Karnataka, it is called mugudu (Tulu: ಮುಗುಡು) and is considered a delicacy.[11]

Neither the Thai nor the Indian population is likely to be the true C. batrachus, however.[4]

A white variation with black patterns is commonly seen in the aquarium fish trade. However, this color variation also is prohibited where walking catfish are banned. Very well-rooted plants and large structures that provide some shade should be included in an aquarium with these fish. Any small tankmates will be eaten by this fish.

• Eel catfish
• List of freshwater aquarium fish species
• List of invasive species in the Everglades

Wikimedia Commons has media related to Clarias batrachus.

• Ros, Wolfgang (2004): "Clarias batrachus - Erfolgreiche Froschwels-Nachzucht im Aquarium", Datz 57 (7): 12-15.
• Ros, Wolfgang (2006): "Clarias batrachus - Auslösen der Fortpflanzung bei Froschwelsen", Datz 59 (4): 33-37.