by Johnny Rader, Marine Science Educator, Sanibel Sea School
You might think catfish are just bottom dwelling pond and lake fish, but did you know there are also species that live in the sea? In fact, it’s not uncommon to find their remains washed up on Sanibel’s beaches. Found globally on every continent except Antarctica, they reside in coastal waters, lakes, rivers, and ponds. Although catfish are a diverse group of ray-finned fish, they all have similar characteristics and adaptations.
These fish are named based on the large, cat-like whiskers – called barbels – that most species have around their mouths. Barbels are essentially taste receptors, used to feel around in muddy and murky waters in search of food. Some catfish have extended barbels, while others are less pronounced. Barbels are not species specific and can also be found on carp, goatfish, hagfish, surgeonfish, zebrafish and sawsharks.
Most catfish are bottom dwellers, eating from the benthic region of the water column. While most other fish are able to control their buoyancy, catfish tend to sink to the bottom. This is due to two adaptive characteristics. First is that they have a reduced swim bladder, which aids many other fish in regulating buoyancy. Second is their heavy, thick skull, which helps pull them to the bottom.
In the Gulf of Mexico, we often find two species – the hardhead catfish and the gafftop sailfin catfish. Both species are common catches in our coastal region, although not usually a favorite of fisherpeople. Each has venomous spines on its pectoral and dorsal fins that can cause inflammation and pain. The pronounced dorsal spine is actually what gives the gafftop sailfin catfish its name. These spines can be easily seen on dried dead fish that have washed ashore, and can sting you even when the fish is no longer alive. When large fish kills occur, catfish stings are a common injury among beachgoers – so be cautious out there, and watch where you walk!