When Fish Go Out for a Stroll

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The Walking Catfish

Believe it or not, there are places in the world where you can go fishing by walking down the street! Especially when it’s dark and rainy. You could saunter along the road and grab yourself a walking catfish.

As its name implies, the walking catfish (Clarias batrachus) is a nocturnal fish that is able to emerge from the water and move around on land. Usually it is grayish brown or gray with tiny white spots, though rare individuals with calico markings and albino coloring have been seen2. The fish lacks scales and has four pairs of whisker – like barbels around its mouth2.  Walking catfish can grow to 24 inches where they are native1. The walking catfish is a rather homely but incredibly tough fish that is able to withstand water conditions that other fish cannot. As an omnivore, the fish is also no picky eater1.

How and Why Walking Catfish “Walk” on Land

The “walk” of the walking catfish is actually more of a wiggling crawl. The fish use their pectoral fins, which have hard structures at their fronts, to pull themselves along land while they undulate their bodies. The movement may look laughably clumsy, but it works1! One crucial element of a walking catfish that gives it the ability to survive on land is called the suprabranchial arborescent organ – so named for its tree – like, branched, shape. The suprabranchial arborescent organ supports the fish’s breathing and works somewhat like a lung. While the gill filaments of a fish would normally collapse outside of water, rendering it unable to breathe, this organ holds up these gill filaments when the fish comes out of the water – hence allowing it to breathe on land.  This means that the fish can survive outside of water so long as it remains moist1.

The ability of the walking catfish to move over land is actually crucial to its survival in its native Southeast Asia, where pools of water frequently form and dry out. When the pool that a walking catfish inhabits dries up, the walking catfish can simply move over land to a new one4. The fish also will  move over land to get to another pool of water which it finds more favorable1.

This video shows walking catfish moving on land.

 

The Walking Catfish in the United States

Although the walking catfish is native to Southeast Asia, its hardiness and ability to move from one body of water to another have led it to thrive in distant places where it has been released accidentally1. This is what would happen when the fish found itself walking around in Florida in the middle of the 1960’s . The first walking catfish in Florida are believed to have either escaped from the Penagra Aquarium in Broward County or to have wiggled to freedom from a truck transporting them between Broward County and Dade Counties (these fish were originally from from Thailand and had been imported to be aquarium pets). It is even possible that both scenarios played out2.

A tiny piece of the vast web of South Florida canals along which the walking catfish could spread.

However the walking catfish arrived in Florida, within 10 years it was in 20 counties. All of the other traits that enabled the fish to do this aside, the catfish was able to take advantage of the interconnected network of canals in South Florida to surge throughout the area with epic speed. Walking catfish are now so abundant in South Florida that there are areas where there are up to 3 thousand pounds of them per acre4!

Walking catfish are known to spread enteric septicemia to other catfish species in Florida.

In areas where walking catfish are brought and become established, their presence can become a nightmare. This is the case in South Florida, where the fish has done harm ecologically and economically. The state’s native catfish and sunfish populations have been damaged. Eggs of various species native to Florida are consumed by the voracious appetites of the fish, harming these species as well. Walking catfish also tend to enter and quickly dominate facilities where fish are farmed commercially- even eating members of the species being farmed in them1!  Another way in which walking catfish wreak havoc in these fish farming facilities is by spreading ESC (enteric septicemia).  This is a disease that walking catfish are known to carry, and they transmit it to the fish that belong in the facility2.

Walking catfish can even jeopardize road travel in Florida! On nights where it rains, these fish tend to move from one body of water to another in large groups. The migrations can pass over busy streets, which is bad news both for the fish and the motorists. The fish are killed in great numbers by the traffic. Meanwhile, the road is blanketed with so many dead fish that it can get slippery & dangerous. This happens on parts of US 411.

Other Hosts to Walking Catfish

Florida is not the only place where walking catfish have landed, multiplied, and become invasive. Other places effected include Pakistan, the Philippines, and Eastern India1.

Isolated Walking Catfish Sightings

There are also other parts of the US where the walking catfish has been found. These locations include the All American Canal (Arizona), the Flint River (Georgia), and a spring in Nevada. Individuals have even been spotted here in New England – in a lake in Massachusetts and in some widely separated bodies of water in Connecticut! Florida, however, is the only US state with a wild population of the fish that has become established2.

rare calico walking catfish

All walking catfish found outside of Florida in the US are believed to be releases from aquariums2. It would seem unlikely that the fish would become a problem in the other places where they have been found in the US, since they are suited to warmer climates and their northward spread even in Florida has slowed1.

Other parts of the US where the walking catfish could potentially cause problems include southern Texas and Hawaii. This is likely why it is now illegal to own1 or transport a walking catfish without federal documentation3.

The Walking Catfish as Food

While walking catfish are generally not eaten in the Western Hemisphere, they are often consumed in their native Southeast Asia. The fact that they can be transported simply in moist bags makes them convenient3. Walking catfish are sought after by individual fishermen in Southeast Asia, and commercially farmed as well2.

Compared to other catfish species, the walking catfish has darker flesh but similar taste. Walking catfish is often used in stews and soups, since its flesh doesn’t fall apart but maintains its firmness when it is cooked. When walking catfish isn’t being cut into chunks for soups, it can be sliced into fillets5. Street vendors in Thailand,  where the fish is widely consumed, sell it fried or grilled. In the Indian state of Assam walking catfish is considered a delicacy, and it also serves as the base for many recipes in Indonesia6.

Fried catfish and shrimp.

Here in the United States, though we don’t consume walking catfish, we do enjoy a delectable variety of dishes made from ” … one of the tastiest fish around (Scripps Networks LLC 2018)”. Catfish can be fried, crusted, or baked in a multitude of recipes7. If you’re drawing a blank for dinner tonight, why not try this unique and delicious fish? You can find catfish frozen and fresh at Atlantic Seafood.

mango catfish tacos

 

 

Works Cited

1. Robins, Robert H. “Walking Catfish”.
Florida Museum, www.floridamuseum.ufl.edu/fish/discover/species-profiles/clarias-batrachus.
Accessed 6 Feb. 2018.

2. Brogan, Christine. “Walking Catfish (Clarius batrachus)
Introduced Species Summary Project (Columbia University), 30 Sept. 2003, www.columbia.edu/itc/cerc/danoff-burg/invasion_bio/inv_spp_summ/Clarius_batrachus.html.
Accessed 8 Feb. 2018.

3. “Walking Catfish: Clarius batrachus.
Florida Fish and Wildlife Conservation Commission, myfwc.com/wildlifehabitats/profiles/freshwater/nonnatives/walking-catfish/.
Accessed 9 Feb. 2018.

4. NYU Journalism. “Fish out of water”.
SCIENCELINE (project of nyu’s science, heatlh, and environmental reporting program),2015,scienceline.org/2014/08/fish-out-of-water/.
Accessesd 9 Feb. 2018.

5. Grygus, Andrew. “Walking Catfish”.
Clovegarden, www.clovegarden.com/ingred/seafishv.html.
Accessed 10 Feb. 2018.

6.”Walking Catfish”.
Wikipedia, 16 Feb. 2018, en.wikipedia.org/wiki/Walking_catfish#As_food.
Accessed 16 Feb. 2018.

7. Scripps Networks, LLC. “Catfish Recipes”.
food network, 2018, www.foodnetwork.com/topics/catfish/.
Accessed 15 Feb. 2018.

8.Valentine, Bob. “Walking Catfish”.
You Tube, uploaded by Bob Valentine, 31 August 2015, www.youtube.com/watch?v=JihqKKIzXR8&t=5s.

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