FunNature & AnimalExtinction of Chinese swordfish confirmed

Extinction of Chinese swordfish confirmed

The hand of man is, once again, behind the extinction of an animal. Now it is the turn of the Chinese swordfish, which has been progressively disappearing from the waters of the Yangtze River since the late 20th century until becoming extinct between 2005 and 2010.

Chinese swordfish lived in the time of the dinosaurs and survived the mass extinction that wiped out the dinosaurs. Their home was the Yangtze River and in its waters they fed on fish and crustaceans. Now, an article published in the journal Science of the Total Environment concludes that the species has become extinct due to overfishing and the construction of dams.

The swordfish population began to decline in the last century due to overfishing. To get an idea, in the 70s each year an average of 25 tons of this large animal was captured , which can measure up to three meters long.

However, the scientists responsible for the study point to the construction of dams, mainly that of Gezhouba, as the culprits of the extinction of the animal. The Gezhouba Dam was built in 1981 on the Yangtze, hampering the journey that swordfish made to lay their eggs in the upper reaches of the river. In this way the fish could not reproduce.

Years passed and the number of swordfish continued to decline. The researchers cite 1993 as the year the animal became functionally extinct. This means that, although it does not disappear from the face of the earth, there are not enough individuals that can reproduce in a meaningful way . Despite this, specimens were still sighted and some were captured with the intention of breeding in captivity. The attempts failed.

The last time a Chinese swordfish was seen was in 2003 , when Qiwei Wei of the Chinese Academy of Fisheries Sciences and the main person in charge of the study and his team attached a tracking tag to a fish accidentally caught near Yibin -South China). Investigators released him to see where he was going but within hours his trail was lost.

Ivan Jaric is a biologist at the Institute of Hydrobiology of the Czech Republic and the University of South Bohemia and co-author of the study. According to him, there may be some specimens of Chinese swordfish swimming around, but it is highly unlikely. “The lack of observations during the studies and during the last 16 years in rivers in highly urbanized regions with a considerable level of water use makes new observations unlikely,” he points out in the study.

The study published in Science of the Total Environment estimates that the extinction of the fish occurred between 2005 and 2010. It also points out that efforts to conserve the animal must have been made before 1993 or at the latest in early 2000, which is when the situation began to escalate.

The Chinese swordfish is related to the American swordfish , which lives in the Mississippi River basin and is in a vulnerable situation . Both are related to the sturgeon family, of which 85% are in danger of extinction. According to the International Union for Conservation of Nature, it is the most threatened group of animals.

The importance of large fish is not only limited to their role within a given ecosystem but they act as guardians of environmental quality, since they can only live in healthy rivers.

The researchers now focus on the rest of the species that live in the Yangtze, because during the study they have not found specimens of another 140 species that they expected to find in its waters. They urge to take action as soon as possible to save the species for which there is still some hope.

Fuente: Extinction of one of the world’s largest freshwater fishes: Lessons for conserving the endangered Yangtze fauna. 2020 Science of The Total Environment. Hui Zhang, Ivan Jarić, David L. Roberts, Yongfeng He, Hao Du,Jinming Wu, Chengyou Wang, Qiwei Wei. DOI: https://doi.org/10.1016/j.scitotenv.2019.136242

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