Walking Fish

Walking fish, sometimes called ambulatory fish, is a general term that refers to fish that are able to travel over land for extended periods of time. The term may also be used for some other cases of non-standard fish locomotion (for example, when describing fish 'walking' along the sea floor, such as the Frogfish or a Gurnard) but a few species, from areas with seasonal water, have evolved this unique ability on land. Most commonly this term is applied to amphibious fish that are able to spend longer times out of water. These fish may use a number of means of locomotion, including springing, snake-like lateral undulation, and tripod-like walking. The climbing perch (Anabas testudineus) has modified gill covers for moving on land. It is often specifically referred to as a 'walking fish', although it does not actually 'walk', but rather moves in a jerky way by supporting itself on the extended edges of these gill plates and pushing itself by its fins and tail. But do not underestimate their achievements as some reports indicate that it can also climb trees! However, as impressive as that sounds, this is undoubtably beaten by the Walking Catfish (Clarias batrachus) that can migrate over land with some ease. 

Despite being known for 'walking on land', the Walking Catfish does not truly 'walk' as most bipeds or quadrupeds do, but has the ability to use its pectoral fins to keep it upright as it makes a sort of wiggling motion with snakelike movements. The real advantage of the Walking Catfish, is that they posses a respiratory system that allows them to live out of water for up to several days to find food or a more suitable environment! In fact, as long as it stays moist, it can survive using this form of locomotion for as long as it needs to. 

The Walking Catfish is originally found primarily in the Democratic Republic of Congo and also Southeast Asia, thriving in stagnant, frequently hypoxic waters (low oxygen conditions) such as ponds and swamps, or slow-moving streams and rivers, or temporary pools. It spends most of its time on, or right above, the bottom surface, with occasional trips to the surface to gulp air. Many of these habitats often dry up and when this happens, its 'walking' skill comes into its own and allows the fish to travel over very impressive distances to discover new sources of water.

Walking catfish are around 30 cm in length and have an elongated body shape. Often covered laterally in small white spots, the body is mainly coloured a grey or greyish 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. This fish also has a hidden embedded sting or thorn-like defensive mechanism behind its fins so needs to be handled very carefully if out for a walk! In the wild, this creature is omnivorous; feeding on smaller fish, molluscs and other invertebrates as well as detritus and aquatic plant. It is a voracious eater which consumes food rapidly and in this habit has become a particularly harmful invasive species. For example, this fish has established alien populations in the southern US and can often surprise drivers by walking across roads at night. Sounds impressive but you wouldn’t want to wait for one on a zebra crossing!