In November 2024, environmental military police in Rochedo, Mato Grosso do Sul, Brazil, observed an extraordinary sight: thousands of bumblebee catfish (Rhyacoglanis paranensis) leaping up the rocks of a waterfall on the Aquidauana River.
These fish scaled vertical walls ranging from 3.3 ft to 13.1 ft high, using rapid body‑flips and tail‑flips to launch themselves forward. Researchers note that the catfish employed a “suction‑cup” mechanism—placing their fins and tails against the rock surface—to create friction and support, a hallmark of an “evolutionary masterclass” in obstacle navigation.
While the exact motivation remains unclear, scientists propose that the catfish were engaged in an upstream migration for breeding—a process known as an “anadromous” event. In this scenario, the fish use the current to locate suitable habitats for egg laying, thus avoiding drought‑affected downstream areas.
After a brief pause in the hot afternoon, the school resumed climbing in the early evening, suggesting that the fish timed their movements to avoid predation and to take advantage of cooler water temperatures.
Rhyacoglanis is a relatively new genus, first described in 2017. The species Rhyacoglanis paranensis was discovered in the upper Rio Paraná basin and is distinguished by its orange‑and‑black coloration and distinct dark bands—earning it the nickname “bumblebee” catfish.
Despite early reports of a wide distribution, recent studies in the Journal of Fish Biology highlight that construction of hydroelectric plants along the upper Paraná may threaten its habitat. The recent waterfall‑climbing event, involving thousands of individuals, is the first large‑scale observation of this behavior and underscores the need for continued field research.
Experts warn that habitat fragmentation and river damming pose significant risks to the species, making further conservation efforts urgent. Ongoing monitoring and ecological studies are essential to protect these delicate ecosystems and the catfish themselves.
