Catfish: the (gentle?) giant seen increasingly in Swiss waters

Catfish have around 1,500 tiny teeth – although none are sharp enough to pierce through human skin. RTS

The catfish is renowned for swallowing up everything it comes across – should humans be worried? Swiss public television, RTS, dived into the Rhône to find out.

With its big head, huge mouth, and 1,500 teeth, the catfish naturally inspires a certain trepidation. Its body – flaccid and without scales – looks almost as much snake as fish. But bathers shouldn’t fret: catfish don’t attack humans, or at least hardly ever…

“Suddenly I felt a large pressure around my stomach which was very, very painful. I said to myself: head for safety, get back to shore,” says Alexandra, who fell victim to a catfish-biting incident in Sion, southern Switzerland, in 2011.

Back on dry land, Alexandra realised things weren’t as bad as feared. “It managed to get off with a bit of my bikini,” she says. “But I wasn’t really bleeding, it was mainly just chafing and painful.”

Protect the nest

Other – very rare – incidents which have been reported elsewhere in Europe all have one thing in common: they happened between May and July, i.e. the period during which catfish reproduce, and when adults protect their nests from invaders.

While catfish don’t eat humans, they do eat (almost) everything else: crayfish, fish, zebra mussels, plants, ducks, snakes, rats, and… pigeons. It even eats itself, or rather, smaller catfish.

“This contributes to a sort of self-regulation of the species, since it has no predators once it reaches adulthood,” says Chloé Vagnon, a biologist who wrote a dissertation about catfish. Many studies have shown that the catfish has no long-term impact on other species, she adds.

Human re-introduction

More and more catfishes are expected to be found in Switzerland in the future, especially in Lake Geneva, where they are spreading fast. Catfish were already present in Switzerland before the most recent ice age, which led to their disappearance. Since then, the species has been gradually reintroduced by humans: firstly at the end of the 19th century in Lake Constance and in the three lakes around Neuchâtel, Biel/Bienne, and Murten. And then 20 years ago in the Rhône river and Lake Geneva.

There are several reasons why it has since thrived in Swiss waters: the absence of predators, climate change, and clandestine releases by certain anglers keen on sporting challenges or big trophies.

World record

The catfish is the third largest fish in the world and the largest in Europe. In 2023, in the Italian river Po, a fisherman snagged a catfish 2.85 metresExternal link in length – a world record.

Thousand-toothed

Unlike pike, catfish don’t have teeth sharp enough to pierce human skin. Its mouth is made up of 1,500 tiny teeth which form a sort of rasp that it uses to grab and hold its prey.

Translated from French by Domhnall O’Sullivan