Deforestation threatens two new fish species with extinction

A new study highlights the excitement and tragedy of discovering two brand new species of fish in Brazil. A team of experts including Murilo Pastana, a researcher at the Smithsonian National Museum of Natural History, described the new species of tiny Amazonian fish – one with striking red-orange fins and the other so small it is technically considered a miniature fish species. The scientists warn that these fish are in imminent danger of becoming extinct, even as the scientific world becomes aware of their existence for the first time. 

During 2015 and 2016, Pastana and his colleagues undertook expeditions into the Brazilian Amazon to search for undocumented fish species in the waterways of the Madeira River Basin which is, according to a 2019 estimate, the richest river basin in the world for fish biodiversity. The survey area, roughly 25 miles north of the Brazilian city of Apuí, is unfortunately almost top of the list of Brazilian municipalities with the highest rates of deforestation. 

“We went to sample places that have never been visited by scientists,” Pastana said. “This area is really important because this is one of the frontiers where deforestation is moving north – the border between new cities and native forest.”

The researchers were able to access the previously unreachable streams, ponds and tributaries using the very same roads that have been created to facilitate logging activities. They camped along the AM-174 road and collected fish using nets, traps and other methods. All the specimens were photographed, cataloged and preserved for further study back at the Museum of Zoology, University of São Paulo.

“It was exciting to find new species,” said Pastana. “But in the field, we saw the forest on fire, logging trucks carrying out huge trees, and cleared patches turned into cattle pasture. This made us feel a lot of urgency to document these species and publish this paper as quickly as possible.”

Pastana is passionate about preserving the country’s biological heritage, and hopes that describing these new species, both belonging to the group of fish known colloquially as South American darters, will motivate the Brazilian government to protect and conserve them, as well as their precious habitat. He and his co-authors, Willian Ohara from the Federal University of Rondônia and Priscila Camelier from the Federal University of Bahia, said that ongoing deforestation in the region places these roughly inch-long fish in imminent danger of extinction. In particular, the more colorful of the two species, Poecilocharax callipterus, is at risk because its known range is limited to a single stream comprising roughly 1.5 square miles of habitat.

To the researchers, P. callipterus stood out immediately in the field as a new species. The fish has a distinctive dark spot just in front of its tail, as well as having bright red-orange fins.  It inhabits the margins of what scientists call black water streams, so named because their waters are stained the color of coffee by tannins leached from fallen leaves. Males of the species have even more intense coloration and sport dorsal fins that can exceed half their body length, which averages just over an inch. Despite searching for this species in the surrounding area on the 2016 return trip, Pastana and his colleagues were only able to find P. callipterus in the single stream in which it was first discovered.

The second species, now named P. rhizophilus, was found among tangles of tree roots protruding from the banks of muddy streams. It has an amber yellow coloration, with males showing dark streaks on their dorsal and anal fins. It is so small that scientists consider it to be miniature, a designation given to fish species that are less than about an inch long as adults. Pastana explained that lab study revealed parts of the skeletons of these tiny fish are actually made of cartilage instead of bone. 

Genetic investigations confirmed the evolutionary relationship of these two new closely related species and their relatives, bringing the total number of species in their small sub-family (Crenuchinae) to five. This is the first addition of a new species to the group in 57 years.

Species from the sub-family Crenuchinae are highly desired by hobby aquarium keepers and Pastana fears that the trade in exotic aquarium fish could pose another threat to the populations of these two previously unknown Amazonian species.  

These fishes, said Pastana, are like works of art and “losing either of these species would be like losing priceless masterpieces.” Like masterworks from Monet or Picasso, each species is full of irreplaceable details that might bear some resemblance to other creatures on Earth but in concert are utterly unique. Extinction would cause all those details, wrought over millions of years of evolution, to be lost forever. “You’d lose everything about these species,” he said.

The study is published in the Zoological Journal of the Linnean Society.

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By Alison Bosman, Earth.com Staff Writer