Large catfish are increasingly frequent in Switzerland due to warming water – some measure up to two meters long. In Bavaria, two catfish recently attacked bathers. But according to the researchers, we must not panic, because this predatory fish is normally fearful.
While shadows and trout often suffer or even die during scorching summers, the catfish begins to activate. “He feels very comfortable when the water temperature reaches 25 degrees,” said Jakob Broodersen of the Eawag Water Research Institute. Due to the consequences of climate change, it could reproduce more quickly in Switzerland and in our neighboring countries. This spring, the biologist equipped for the first time with an 80 -cathed transmitter in Swiss waters in order to study more precisely the behavior of these predatory fish.
Big mouth and a great appetite
These giants devour almost everything that can enter their mouths – whether fish, a rat or a small duck. “In France, I have even found a turtle and a snake in the stomach of a catfish,” said the EAWAG researcher. In Switzerland, the catfish has mainly been established in the Rhine and the AAR, as well as in their greatest tributaries such as limmat. It is also present in large numbers in large lakes such as Lake Geneva, Lake Neuchâtel, Lake Zurich or Lake Greifen. According to the Federal Office of the Environment (OFEV), no less than 7,622 catfish was caught in 2023. For comparison, ten years ago, this figure was 1432 catfish, and twenty years ago, only 506 catfish.
Do not give in to panic
At the end of June, at Lake Brumbach in Bavaria, a catfish over 2 meters long and weighing 90 kilos attacked and wounded at least five bathers. After several unsuccessful attempts to chase him, a police officer must finally cut him with his service weapon. Two fishermen called in reinforcement then took out the huge fish from the lake using a boat, allowing the reopening of the bathing area. This week, a new catfish attack has occurred there. A 69 -year -old swimmer was bitten on the arm and suffered a bloody cut. As an immediate measure, an inspection by echrosurer along the lake centers must now discover other frights in order to ensure the safety of bathers.
According to researcher Jakob Broadersen, this is an accumulation of unfortunate coincidences at Lake Brombachsee. The fish are certainly sometimes extremely large, but they would be rather timid in general and, unlike the pike, have no sharp teeth. You should not give in to panic when you bathe in rivers or lakes. It is important that swimmers remain calm and do not quispire in the water if they meet a catfish. Normally, nothing happens, assures the researcher.
A great predator for other species
In many places, catfish has been actively reintroduced into Swiss waters by humans. However, with its growing domination, species such as trout or barbeau are increasingly under pressure. “As a super predator, it also changes the entire food network with its large appetite,” said Jakob Broodersen. Until now, we do not know the long -term effects of this phenomenon and on the need for targeted management.
![With this boat, researchers fish catfish in the AAR before releasing them. [Eawag]](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///ywAAAAAAQABAAACAUwAOw== "With this boat, researchers fish catfish in the AAR before releasing them. [Eawag]")
Alexander Brinker, from the Lazbw Fisheries Research Center in Langenargen on Lake Constance, explains that the more hot it is, the more the catfish develop. “On the other hand, when it is cold, the catfish becomes inactive, remain at the bottom of the water and no longer eat,” said the researcher. However, with the increase in water temperatures, they do not only gain length, but especially in weight. In warmer regions, giant catfish over 2.5 meters long and approximately 100 kilos have already been captured.
Selfies with catfish
Despite the ecological risks, the catfish is celebrated by many fishermen. Its impressive size and strength make it a cult trophy, especially on social networks. Videos of spectacular sockets and daring hunts from the banks always attract many fans. According to Jakob Brodersen: “It’s a big challenge to get this giant fish out of water.”
Due to the increase in surface water temperatures, catfish does not only prosper in Switzerland, but also in European rivers. “It grows faster, reproduces more often and conquers new territories,” explains Alexander Brinker. Sower does not only have an advantage compared to other fish in hot waters, but especially when they are disturbed or ecologically disturbed. It is relatively insensitive and remains in great shape while other animals have long been weakened.
Barbara Ree (SRF)
