The official scientific declaration of a species’ extinction is a somber milestone, marking the definitive end of an evolutionary lineage. Extinction, in a global scientific context, means that exhaustive surveys have concluded with reasonable certainty that no individuals of the species remain anywhere in the world. This classification, known as Extinct (EX), differs from Extinct in the Wild (EW), where a species survives only in captivity. Such declarations follow years or decades of systematic, failed searches, not just the last sighting. The year 2022 saw the formal recognition of the loss of a unique freshwater giant.
The Specific Species Declared Extinct
The animal officially declared Extinct by the International Union for Conservation of Nature (IUCN) Red List in July 2022 was the Chinese Paddlefish, Psephurus gladius. This massive freshwater fish, often called the “Giant Panda of the Rivers,” was endemic to the Yangtze River basin in China. It was a member of an ancient lineage, the paddlefish, that had existed for at least 200 million years, predating the dinosaurs.
The Chinese Paddlefish was one of the largest freshwater fish species in the world, with documented records of individuals reaching up to 7 meters (23 feet) in length and weighing nearly half a ton. Its distinguishing feature was an elongated, paddle-like snout, or rostrum, that could account for one-third of its body length. This unique sensory organ was used for detecting weak electrical signals generated by its prey, making it an apex predator.
The last confirmed sighting occurred in 2003, when an adult specimen was accidentally captured and subsequently tagged by researchers near Yibin. However, the tag’s signal was lost shortly after the fish was released, marking the final documented record. The 2022 IUCN update officially finalized its classification, confirming the loss of the sole species within the Psephurus genus.
The Scientific Criteria for Extinction Declaration
The process for declaring a species extinct is governed by the International Union for Conservation of Nature (IUCN), which uses the Red List of Threatened Species as the global standard. The IUCN criteria categorize species into nine levels, ranging from Least Concern to Extinct. This framework ensures that any classification is based on explicit, objective evidence rather than conjecture.
To move a species into the Extinct category, assessors must establish that there is “beyond reasonable doubt” no remaining individual. This certainty is achieved by requiring “exhaustive surveys” across the species’ entire historical range and in all known or expected habitats. The timeframe for these surveys must be appropriate to the species’ life cycle, which, for a long-lived fish like the Chinese Paddlefish, demanded an extended search period.
The category of Data Deficient exists for species where information is inadequate to assess extinction risk. A species is only moved from a threatened category like Critically Endangered (CR) to Extinct (EX) after conclusive failure to find any individuals. This rigorous approach prevents premature declarations while acknowledging that a lack of sightings over a sufficient period can be statistically significant. The official designation reflects a scientific consensus following a multi-year review of all available data and survey efforts.
Environmental Factors Contributing to the Loss
The demise of the Chinese Paddlefish can be traced primarily to the construction of large-scale infrastructure along the Yangtze River, combined with unsustainable resource use. The species was anadromous, meaning it migrated upstream from the lower river and estuary to specific areas in the upper river to spawn. This life cycle made it highly vulnerable to habitat fragmentation.
The construction of the Gezhouba Dam, which began operating in 1981, proved to be the decisive factor in the species’ extinction. This massive barrier was built without any functional fish passage, physically blocking the paddlefish’s mandatory migration route to its upstream spawning grounds. The dam effectively separated the fish population, preventing reproduction and sealing its fate.
While the dam dealt the final blow, severe overfishing had already decimated the population throughout the 20th century, with annual harvests reaching 25 tonnes in the 1970s. The combination of habitat loss due to dam construction, which eliminated spawning areas, and the intense fishing pressure on the remaining downstream population was an impact the ancient species could not withstand. This loss highlights the vulnerability of migratory river species to large-scale development projects that alter natural waterways.