Five times more fish at risk of extinction than previously thought

(CN) — The number of fish species facing the threat of extinction has been dramatically underestimated, according to a study published Thursday.

The International Union for Conservation of Nature estimated that 2.5% of marine teleost fish species — by far the largest infraclass of ray-finned fishes —are at risk of extinction, but researchers now say that figure is more like 12.7%.

A team of scientists from the Marine Biodiversity, Exploitation and Conservation Unit in Montpellier, France, conducted research on the fate of these fishes. The study, published Thursday in the journal PLOS Biology, took a comprehensive look at fish species previously excluded from extinction predictions due to a lack of data.

The International Union for Conservation of Nature maintains its Red List of Threatened Species to help guide conservation efforts and focus attention on the species most threatened. Of the 150,000 species tracked on that list, marine fish species had the highest percentage of species unable to be classified due to insufficient data, with 4,992 species lacking enough data to qualify for official conservation status.

Nicolas Loisea and Nicolas Mouquet, two of the lead scientists behind the endeavor, targeted those 4,992 data-deficient fish species in the study. To gain more information about the fish species, the researchers combined an artificial neural network with a machine learning model to predict extinction risks.

The researchers used biological traits, occurrence data, taxonomy and human uses from 13,195 species to train the models.

Of the 4,992 species, 78.5% were categorized as non-threatened or threatened. These terms include designations such as endangered, critically endangered and vulnerable — all categories used by the International Union for Conservation of Nature.

The results from the categorization saw an increase in predicted threatened species from 334 to 1,671. Predicted non-threatened species increased by about a third, from 7,869 to 10,451.

Among the species predicted as threatened, many were from cryptobenthic fish families like gobies, clingfishes and blennies. These fishes are key ecological players, particularly when it comes to reef ecosystems and trophic interactions.

Scientists said certain species within those fish families may be undergoing a “silent extinction” process due to their elusive behavior and certain habitats that hamper the assessment of their populations.

The species that ended up on the predicted threatened species list tended to have a large body size, low growth rate and small geographic area, according to the study. In addition, fish species with a preference for very shallow habits had an increased likelihood of being threatened.

The researchers identified hotspots for predicted threatened species in the South China Sea, the west coasts of Australia and North America and the Philippine and Celebes Seas. The scientists suggested those regions prioritize creating or bolstering effective marine protected areas and increase research efforts.

The scientists acknowledged that modeling is not a permanent substitute for direct evaluation of species extinction risk, but asserted that it provides a cost-effective and rapid evaluation of extinction status. The models help scientists focus on the species at the most risk and know which ones to prioritize.

“Artificial Intelligence enables the reliable assessment of extinction risks for species that have not yet been evaluated by the International Union for Conservation of Nature (IUCN),” Loiseau said in a statement accompanying the study.

The scientist characterized the jump in estimated marine fish species facing extinction risks as “significantly higher” than previously thought and offered insight into how additional research may benefit the study.

“We propose to incorporate recent advancements in forecasting species extinction risks into a new synthetic index called ‘predicted IUCN status.’ This index can serve as a valuable complement to the current ‘measured IUCN status,’” Loiseau said.