Their Latin name is Rhyacoglanis Pararansisin English they are called “bumblebee catfish”, that is “cat fish that resemble a bomb”, and live in the basins of the great rivers of South America. They are small, colored precisely as a bomb and, above all, they are very difficult to observe, so much so that until recently we knew very little about their lives, and in particular of their migratory behaviors.
An empty filled thanks to the environmental police of the Brazilian state of Mato Grosso do Sul, who observed them for the first time as they scaled a waterfall (The video is below) and reported the behavior to the scientists of the Federal University of Mato Grosso do sul. Who have documented this “first time” in a study published on Journal of Fish Biology.
Mato Grosso cat fish. Rhyacoglanis Pararansis He lives in the basins of the Amazon Rio, Orinoco and Rio de la Plata. They are family catfish Pseudopimelodidae And they are among the youngest ever: they do not reach 10 cm in length. Their dimensions, and the fact that they are less important than other species for the fishing industry, makes them animals that are little studied, as well as difficult to observe in nature. Their migrations, in particular, had never been observed before: they are very quick events and occur only in very specific environmental conditions.
The environmental police of Mato Grosso in 2024 noticed for the first time that, in a waterfall of the Aquidauana river, thousands of specimens of these cat fish were gathering, in an attempt to climb it.
Ventose effect. The team of researchers who studied the phenomenon was able to learn a lot about the migration of these little cat fish. For example, which take place only towards the evening: from day it is too hot, and the fish spend the time hidden under the rocks. Towards six in the evening, on the occasion of the sunset, they leave their hiding places and begin the climb of the waterfall. How do they do? According to the authors of the study, they exploit the windy effect to stick to the rock with the belly, then they begin to climb it by moving the body on the side and pushing itself upwards with the fins.
Why all this effort? As regards the reason for this behavior, which in some points brings cat fish to climb wet rocks even four meters high, the authors of the study have a hypothesis: it is a reproductive behavior, in the sense that the fish date back to the waterfalls to find themselves in the same place and mate – probably taking advantage of the end of a long drought that had affected the region in the previous months.
