Brazilian researchers uncover new cloud fish habitats

Scientists hailing from the Fish Ecology Laboratory at the Federal Rural University of Rio de Janeiro (UFRRJ) have recently pinpointed three previously unknown locations where the cloud fish, a group of rivulids comprising over 300 species scattered across Brazil, can be found. Of this total, 130 species are threatened with extinction, as per the official species list published by the Ministry of the Environment. Consequently, they occupy the top spot for the highest number of endangered species within the Brazilian fauna.

Among these three newly discovered sites for the Notholebias minimus species in the state of Rio de Janeiro, one lies within the protective embrace of the Brisas Environmental Protection Area (APA) in Sepetiba Bay, while the other two are nestled in the municipality of Seropédica, one of which graces the university campus itself.

These breakthroughs stem from the doctoral research conducted by Gustavo Henrique Soares Guedes within UFRRJ's Postgraduate Program in Animal Biology. These findings have been hailed as a cause for celebration, given the species' precarious position on the brink of extinction in the wild.

In an interview with Agência Brasil, Gustavo Guedes explained that the Notholebias minimus species is endemic to Rio de Janeiro. "It doesn't exist anywhere else in the world," he said. The fish are small, colorful, and increasingly rare. They reach a maximum length of four centimeters. 

Guedes further elaborated that the entire coastal plain of Rio de Janeiro, stretching from Copacabana to Seropédica, historically comprised marshes that served as the habitat for this cloud fish species, Notholebias minimus. He remarked, "We still have many records today in Barra da Tijuca due to the slow pace of urban expansion."

Threats to species

Threats to these species loom large, exacerbated by limited knowledge regarding cloud fish, which constitute the most endangered group of fauna in Brazil. This stems partly from habitat loss and degradation, particularly in the Atlantic Forest, where human activity has decimated numerous wetlands hosting these species. Additional emerging threats include climate change, invasive species, and pollution.

Guedes revealed the peril of fish trafficking as another menacing threat, with traffickers primarily dealing in cloud fish eggs rather than the fish themselves. "They don't send the fish to Europe or the United States; they send the eggs, which can even be sent by post." For this reason, Guedes said it is very difficult to detect the trafficking of these animals. "And this is also one of the threats, because many traffickers take these fish out of the environment, breed them in aquariums, take the eggs and sell them around the world." The eggs are remarkably resilient, and capable of surviving without water for up to six months.

Researcher Gustavo Guedes /UFRRJ

Life cycle

These cloud fish boast a unique life cycle, alternating between aquatic environments during the rainy season and terrestrial habitats during the dry season. Guedes explained, "They exhibit a strong zonality in their life cycle, occupying temporary wetlands during specific times of the year. When the environment dries out, these fish reproduce, depositing their eggs in the soil, which boasts remarkable resilience. These eggs remain buried for months without water. When the rains return, these fish hatch and repopulate the aquatic environment. In times past, before scientific knowledge prevailed, the popular belief was that these fish descended from the sky with the rain, hence earning them the moniker 'cloud fish.'"

Mapping initiative

Gustavo Guedes and his team are going to map cloud fish all over Brazil to try to uncover new habitats harboring these imperiled species. Establishing conservation units stands as an effective strategy to safeguard these fish while assessing their vulnerability to climate change. Fieldwork is slated to commence next October in the Lakes Region of Rio de Janeiro, timed to coincide with the onset of seasonal rains.

The latest data regarding these fish's distribution is accessible through the Brazilian Biodiversity Information System (SIBBr) and the Global Biodiversity Information Facility (GBIF), digital platforms that integrate open data pertaining to biodiversity and ecosystems.