First official extinction of 2020 – one of the largest freshwater fishes

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In the latest paper, a group of scientists led by Hui Zhang of the Chinese Academy of Fishery Sciences in Wuhan China argued that the Chinese paddlefish is no more. The Chinese paddlefish, which is one of the largest freshwater fishes probably might have gone extinct between 2005 and 2010. The fish was once common in the Yangtze River in China, the researchers wrote, but overfishing and habitat fragmentation sealed the species’ doom. And there is no hope for bringing it back. 

Zhang and his colleagues wrote in a paper of the journal Science of the Total Environment, “The fish should be considered extinct according to the IUCN Red List criteria as no individuals exist in captivity and no living tissues were conserved that could help with potential resurrection,”.

The Chinese paddlefish was one of the most impressive creatures with a large protruding snout. The nose of the Chinese paddlefish gave it one of its nicknames, “Elephant Fish” or “Xiang yu”. The paddlefish could grow as long as 23 feet (7 meters), according to anecdotal evidence.

Paddlefish were caught regularly in the Yangtze River as late as the 1970s, according to Zhang and his colleagues. In 1981, a major dam, the Gezhouba Dam, was built in the river and split the Chinese paddlefish population in two. 

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The Gezhouba Dam also prevented fish trapped below it from swimming upstream to tributaries where they could release eggs. The species was listed as one of China’s most threatened animals in 1989, but the population continued to decline despite that listing. The last sighting of a Chinese paddlefish was in 2003. 

Now, Zhang and his team of scientists wrote, “the paddlefish is officially gone”. The researchers scoured records of sightings dating back to 1981 and conducted field surveys in 2017 and 2018 of the Yangtze and its tributaries and lakes: the Yalong River, the Heng River, the Min River, the Tuo River, the Chishui River, the Jialing River, the Wu River, the Han River, Dongting Lake and Poyang Lake. The researchers set up fishing nets to capture species in these waterways and surveyed local fish markets, looking for evidence that this paddlefish species might still be caught. 

Research

The researchers found 332 species of fish but not a single Chinese paddlefish. The historical sighting data suggested that a few of the paddlefishes were seen after 1995. The evidence suggested that the fish upstream of the dam became functionally extinct — unable to reproduce in the natural environment — by about 1993. The species hung on until around 2005, or perhaps 2010 at the latest, the researchers said. 

The loss of the Chinese paddlefish holds lessons for how to ensure the survival of other threatened Yangtze species, the researchers wrote. First, more-frequent surveys of the river basin would allow scientists to keep closer tabs on what species are struggling. Before the 2017 survey conducted by Zhang and his team, the last comprehensive fish survey of the Yangtze and its tributaries occurred in 1975. The second thing is that the rescue efforts should begin much quickly, the researchers wrote. Most of the intense work done to save one of the largest freshwater fishes started after 2006, likely after the Chinese paddlefish was gone. To prevent the species’ extinction, rescue efforts should have started before 1993, when the fish became functionally extinct, the researchers said.