Rainy Season Reminds Us that Fish Can Walk
During the onslaught of heavy rains on Sanibel, some remarkable things can be seen. Everything from frogs, crayfish, and fish emerge to take advantage of the sudden abundance of fresh rainwater. Perhaps you have seen a walking catfish (Clarius batrachus)? This invasive fish from Southeast Asia is (unfortunately) very common on the island, where it is often seen “walking” from waterbody to waterbody in both residential and protected areas. Last week, SCCF Wildlife & Habitat Management Director Chris Lechowicz captured a video of one moving across a residential Sanibel driveway after a heavy rain event.
The walking catfish has been documented on the island since the 1970s, although it was first documented in Broward County in the 1960s in Florida. This was a common aquarium fish that escaped from fish farms and was released from aquarists who no longer wanted them—and they quickly spread around Florida. This is the only catfish, which reaches 20 inches in length, found in the freshwater bodies on Sanibel.
This species “walks” or wiggles across the landscape by using their pectoral fins to elevate their body above the ground and twist like a snake to move forward. They use a specialized gill to breathe air while not in the water. Walking catfish are distinctive from others: They have an elongated dorsal fin that runs almost the whole length of the body. These fish also produce a distinct sound while on land that sounds like “clicking.” Like other fish species in the taxonomic order Siluriformes (catish), this catfish has barbels (whiskers) around the mouth for feeling for food along the bottom of murky waterbodies. Walking catfish are mostly brown in color; however, white individuals (albino) are sometimes seen.
These invasives spread to new areas quickly and are considered an aquaculture nuisance because they infiltrate manmade ponds used to reproduce fish. They quickly dominate the ponds by eating all the fish and are nearly impossible to eradicate.