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Saturday, April 4, 2009

Walking catfish

The walking catfish, Clarias batrachus, is a species of freshwater airbreathing catfish found primarily in Southeast Asia, so named for its ability to "walk" across dry land, to find food or suitable environments. While it does not truly walk as most bipeds or quadrupeds do, it has the ability to use its pectoral fins to keep it upright as it makes a sort of wiggling motion with snakelike movements. It can survive using this form of locomotion as long as it stays moist. This fish normally lives in slow-moving and often stagnant waters in ponds, swamps, streams and rivers (Mekong and Chao Phraya basins), flooded rice paddies or temporary pools which may dry up. When this happens, its "walking" skill comes in handy for moving to other sources of water.

Characteristics and anatomy

Walking catfish are around 30 cm (a foot or so) in length and have an elongated body shape. Often covered laterally in small white spots, the body is mainly colored a gray or grayish brown. This catfish has long-based dorsal and anal fins 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.

One main distinction between the walking catfish and native North American Ictalurid catfish is the walking catfish's lack of an adipose fin.

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

A certain collective species of walking catfish found primarily in the vicinity of the Panama islands and southern America are large enough that they use their long whiskers as tentacle-like mechanisms. Some walking catfish use these “tentacles” to prey on smaller marine animals and even use them in their aid of walking”. Some rumors suggest that these catfish use their tentacle-like whiskers to pry open wires protecting private bodies of water to enter and prey on unsuspecting fish.
Magur - Clarias batrachus - sold in HAL market, Bangalore

Location and habitat

The walking catfish is a native of South East Asia including Malaysia, Thailand, eastern India, Sri Lanka, Bangladesh, Burma, Indonesia, Singapore, and Borneo. It was probably introduced into the Philippines but now it is common elsewhere in this country. During its season in the Philippines, it is widely distributed throughout the country and many consumers buy this product alive. The catfish is a tropical animal and prefers a water temperature in the range of 10 - 28°C.

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

Diet and eating habits

In the wild, the natural diet of this creature is omnivorous; it feeds on smaller fish, mollusks and other invertebrates as well as detritus and aquatic weeds. It is a voracious eater which consumes food rapidly and this habit makes it a particularly harmful invasive species.

As invasive species

In the United States it is a nonindigenous invasive species, which is now established in Florida and reported in California, Connecticut, Georgia, Massachusetts, and Nevada.

The walking catfish was imported to Florida, reportedly from Thailand, in the early 1960s for the aquarium trade. 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 that this species has been sold by tropical fish dealers in California for some time. They have also been spotted in the midwest a couple of times.

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

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