Armored Catfish: Plecos, Invasions and Why Not to Release

Armored catfish are the family Loricariidae, the largest catfish family, with over 90 genera and just over 680 species from Costa Rica, Panama and tropical South America (Wikipedia). In shops they are sold as plecos. Instead of scales they have bony plates, and the mouth is a sucker on the underside of the head, lined with small bumps called papillae, used to hold on in fast water and scrape algae, invertebrates and detritus. Some Panaque species even eat wood.

Sizes vary enormously, from 2.22 cm in Nannoplecostomus eleonorae to over 100 cm in the largest (Wikipedia). The ones that escape into US waters are mostly the big species: Texas State University's invasive species team names the common pleco, Hypostomus plecostomus, and the Parana sailfin catfish, Pterygoplichthys anisitsi, in Texas, with specimens from 3 inches to over 3 feet. Florida's Fish and Wildlife Conservation Commission (FWC) describes sailfin catfish over 20 inches and 3 pounds with a worm-like pattern of dark markings on the head.

Yes. It sounds invented because of viral photos of a spiny, plated fish, but armored catfish are an ordinary, well-studied family. The plates are bony armour that replaces scales (Wikipedia). If you have caught one in a river in the US, Asia or elsewhere outside the Americas, it is almost certainly an escaped or released aquarium fish.

Because released plecos set up breeding populations that damage rivers and native fish, which is the reason rules against dumping aquarium fish exist; check your state or national law for the exact rule where you live. The documented harm (Texas State University; Florida FWC; Wikipedia):

• Bank erosion: males dig spawning burrows into shorelines, sometimes undermining canal banks and lake shores
• Competition: they can outcompete native species, and Texas State University warns of a possible collapse of freshwater fisheries
• No real benefit: their effectiveness at controlling algae in natural waters is undocumented
• Fast breeding: over 300 eggs per spawning cycle with high survival

In Texas they are established in the San Antonio and San Marcos rivers, Comal Springs and Houston bayous, and the state has used aggressive removal fishing since 2016. The message from Texas State University is simply 'Never dump your tank.' If a pleco outgrows your tank, rehome it through a fish shop or aquarium club.

Not live, but survive for a surprisingly long time. Some loricariids can breathe air through a modified part of the digestive tract; Wikipedia says Pterygoplichthys can survive up to 30 hours out of water, and Texas State University gives more than 20 hours. Most species use air breathing only under stress. This is one reason they spread: they can survive stagnant, low-oxygen water and being moved between waters. Do not assume a pleco left on a bank is dead.

It is eaten, but it is awkward to prepare. Florida FWC rates sailfin catfish edibility as fair to good, says they are difficult to clean and best cooked whole 'in the shell', after which the white, flaky meat slides out, and sets no bag or size limits. Before eating any, check where it came from: plecos often live in urban canals and drainage water, so follow your local fish consumption advisory, and never eat an aquarium fish that has been medicated.