With the passage of time, the banks of the river were covered with bamboo, which has slowly brought the giant panda to become part of the ecosystem. In the last few millennia, a blink of an eye in evolutionary time - the Land was inhabited by billions of people and China has become the most populous country on the planet. In the muddy waters of the Yangtze, the swordfish has lived using his snout like a sword to sense the electrical activity and track the prey, such as crustaceans and fish. The new study concludes that the species is now extinct, mainly due to overfishing and construction of dams.
And' "a loss is reprehensible and irreparable," says the main author of the article Qiwei Wei of the chinese Academy of fisheries sciences, that studies the animal for decades. "It's very sad," adds Zeb Hogan , a biologist for the fish of the University of Nevada, Reno, as well as explorer of the National Geographic are not directly involved in the study. "It is the ultimate loss of an animal is really a unique, extraordinary, without any hope of healing," he adds. Hogan says that the extinction of the fish sword should serve as a warning bell to protect other freshwater species. Large fish, in which it is specialised, are particularly at risk.
"This is the first of these large freshwater fish to disappear, and many are at risk: the concern is that others will die, but the hope is that we can reverse their decline before it is too late," says Hogan. The species is gradually decreased in the course of the last century due to overfishing. In the years '70 were collected on average 25 tons of swordfish each year. According to the researchers, the species is extinct between 2005 and 2010, but an intervention prior to the new millennium, he would have, perhaps, avoided the loss.
The research team has tried to find the fish sword, chinese in hundreds of places along the Yangtze. Have been used various types of networks, echo sounder, equipment for electro-fishing and other techniques to locate any representative of the species, all in vain. Also the fish markets of the country were monitored. The researchers then used a mathematical model to determine the probability that the species is extinct, depending on the size of the population, the previous and the intervals between sightings. "We hope that there are still specimens of swordfish chinese, but the chances are decidedly poor. The lack of observations over the past 16 years and in the rivers, in regions that are highly urbanized, with a significant level of use of the water makes it highly unlikely new observations," says Ivan Jaric , co-author of the article and a biologist at the Institute of hydrobiology, Czech and the University of south Bohemia. The swordfish chinese was one of only two existing species, its closest relative is the fish marsh american, a vulnerable species found in the Mississippi river basin in the United States.
Both are closely related to the sturgeon, threatened to 85 percent, which makes them the species most at risk, according to the International Union for Conservation of Nature. "The large fish are not only crucial elements in their ecosystems, they are also sentinels for environmental quality, because it can only survive in the rivers healthy," says Hogan.
The teaching of the disappearance of the swordfish must be the importance of protecting the heritage that is now in the Yangtze, and not only. "We must act with urgency to save those species for which there are still a few possibilities," said Jaric. "They should be conducted as soon as possible of the assessments of the risk of extinction for all species at risk in the Yangtze," says the researcher. "Going forward, we have to learn to balance the needs of humans with those of aquatic life," says Hogan. "And it is not an impossible task," he concludes.
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