Baiji dolphin: It is an aquatic mammal in the order Mammalia and Cetacea. "Ji" sounds like jì; the media often writes it as " white-tip dolphin ", which is a small freshwater whale unique to China. The body is spindle-shaped, 1.5-2.5 meters long, and weighs up to 230 kilograms. The snout extends forward like a bird's beak, narrow and long, with the tip of the snout slightly upward, about 30 cm. The forehead is significantly raised, and the nostrils are on the top of the head. When breathing, water comes out of the head first, and the water spray is not high. The eyes are extremely small, located behind and above the corners of the mouth. The ear holes are pinhole-shaped. The dorsal fin is triangular, the fins are wider, the ends are blunt, and the caudal fin is crescent-shaped. The back of the body surface is blue-gray, the ventral surface is white, and the tail fin does not come out of the water.
Mainly live in the middle and lower reaches of the Yangtze River in China and the Dongting Lake, Poyang Lake, Qiantang River and other waters connected with it. They usually live in pairs or more than 10 together. They like to move in deep and rapid places and are good at diving. The Baiji dolphin is a carnivore with about 130 sharp teeth in its mouth, which are the same type of teeth as and . It feeds on freshwater fish and often swims to the shore in shallow water to hunt at dawn and dusk. Also eats small amounts of aquatic plants and insects. When breathing, the head comes out of the water first, and then the whole body is exposed to the water. After swimming 2 meters on the water, enter the water again. The lifespan can reach more than 30 years.
Baiji dolphins evolved from terrestrial animals in a long evolutionary process and are the rarest of all whales in the world. On November 14, 2018, the " IUCN Red List of Endangered Species " was updated and released. The Baiji dolphin has not yet been confirmed to be extinct, and the original rating of "critically endangered" remains.
Dr. Sam Turvey of the International Union for Conservation of Nature conducted surveys along the Yangtze River in China, trying to discover the reasons behind the Baiji dolphin disappearance and the decline of other Yangtze River species.
While interviewing fishermen along the Yangtze River as part of an intensive investigation into the possibility of the Baiji dolphin becoming extinct, researchers discovered the carcass of a finless porpoise on the river bank near the port in Poyang's Hukou County. Detailed studies of dead animals could provide valuable clues into the factors that led to the disappearance of the baiji dolphin and the ongoing severe decline in the population of the world's only freshwater finless porpoise.
It's not a pretty sight, and it's obvious from the current situation that researchers were told the finless porpoise had been lying on the river bank for about 30 days. The researchers applied ointment to their noses to mask the stench of the dead animals and then began studying the dolphin's autopsy. Fortunately, we experienced extremely cold weather some time ago, so the finless porpoise did not rot badly.
The animal is an adult female with a body length of 150 cm. There were no external markings to indicate it had been struck by a boat or entangled in fishing gear. Looking at the guts, the researchers found no broken ribs or side bleeding indicating a vessel collision, or lung foam indicating bycatch (bycatch is a term used in fisheries to refer to when fishermen inadvertently target other marine species. Captured animals. Bycatch includes animals that are caught and released and animals that die accidentally as a result of fishing operations) drowning. The animal had healthy levels of blubber and had several indigestion fish in its stomach, suggesting it had been eating normally and was actively searching for food shortly before its death. The finless porpoise was therefore apparently in good health before death, which appeared to be acute and sudden, but with no obvious evidence of trauma, as would be expected from bycatch in fishing gear or vessel collisions. Therefore the animal was most likely killed by electrocapturing.
Electrofishing is an illegal fishing method that became widespread in the Yangtze River region in the 1990s. It is usually practiced by people with no "real" fishing skills who work at night and use batteries to fire large charges into the river, collecting any dead fish that float to the surface. It is extremely destructive, with a lethal charge that can kill anything within 20 meters, and the charge continues to flow in the water as the fishing boat drifts down the river. Professional Yangtze fishermen despise electric fishermen. But while local fisheries officials told us they are focusing on controlling electrofishing, they have limited staff and have not yet been able to conduct comprehensive “trap operations” or regularly survey river sections for regulation.While there are ongoing covert operations to try to identify fishermen in riverside communities, these are also very limited.
As the researchers traveled from one riverside fishing village to another, more and more data were collected about other finless porpoise carcasses that fishermen and regional fisheries bureaus had seen over the past few years. Researchers are currently analyzing all the data collected during the investigation, but it appears that the finless porpoise's death was caused by a range of different factors. The two most common causes of dolphin deaths are vessel collisions and incidental catch in fishing gear, as far as researchers' surveys know. These two factors must be the cause of the massive death of Yangtze finless porpoise . As early as 1892, a European observer reported that Yangtze River fishermen used rolling hooks and long lines to fish in the water, and "sometimes unfortunately the entire line was broken by the hook of the finless porpoise living in the Yangtze River." Throughout the 20th and 21st centuries, as China's population grew, so did fishing intensity and the associated death toll of finless porpoises. Industrialization in the Yangtze River region also led to a massive increase in ship traffic, causing finless porpoises to lose their hearing and become Become a dead animal on the road.
However, some causes of finless porpoise mortality are more obvious than others. Non-expert fishermen are more likely to identify dolphin deaths caused by propeller strikes or entanglement in fishing gear than less obvious causes of death like pollution or electrocution, which leave no external traces. Further analysis will investigate whether it is possible to tease out the relative impact of these different threat factors from the researchers' interview data.
But the finless porpoise is not the only cetacean in the Yangtze River. The main purpose of the researchers' investigation is to investigate the disappearance of the Baiji dolphin, a unique finless porpoise in the Yangtze River.
