Some time ago, the news about the appearance of the Yangtze River finless porpoise rushed to the hot search. During their daily inspections, Wuhan Fishery Administration law enforcement personnel found that in the Jinkou section of the Yangtze River, there was a group of finless porpoises flipping and jumping back and forth on the sparkling river surface, chasing and preying on small fish and shrimp. According to the staff, this is the first time that the Yangtze River finless porpoise has appeared in groups after the implementation of the "ten-year fishing ban" plan.
The Yangtze River finless porpoise that appears in pairs
Do finless porpoises only have in the river?
As an aquatic mammal endemic to the Yangtze River Basin, many people think that finless porpoises are only found in rivers and lakes. But in fact, the finless porpoise belongs to the order Cetacean, toothed whale suborder, porpoise family, Porpoise genus (Neophocaena), some molecular evidence even shows that the porpoise is the most basic branch of the porpoise family, through evolution gradually inhabit different aquatic niches, so now worldwide, the figure of the finless porpoise throughout the northwest Pacific Ocean and the Indian Ocean coastal waters, and in China, almost all offshore waters have their figures, such as the Bohai Sea, the Yellow Sea, the East China Sea, etc., especially a population scattered into the Yangtze River, Formed the world's only freshwater finless porpoise population, which is what we often call the Yangtze River finless porpoise.
Yangtze Finless Porpoise
Despite its widespread distribution, only two species in the genus are currently recognized by the Taxonomy Committee of the Society of Marine Mammals (based on morphological and molecular biological data). That is, there are two species: the broad-ridged finless porpoise (N. phocaenoides, abbreviated as the Indo-Pacific finless porpoise) and the N. asiaeorientalis. Among them, the broad-ridged finless porpoise is mainly distributed in the shallow waters of the Indian Ocean and Southeast Asia, with the westernmost footprint reaching the Persian Gulf and the easternmost reaching the Taiwan Strait, while the narrow-ridged finless porpoise is divided into 2 subspecies, namely the East Asian finless porpoise (N. a. sunmeri) and the Yangtze River finless porpoise (N. a. asiaeorientalis), the East Asian finless porpoise is distributed offshore China, and the Yangtze River finless porpoise lives in the middle and lower reaches of the Yangtze River and its large tongjiang lakes such as Dongting Lake and Poyang Lake. Even more than 1,000 kilometers up the Yangtze River to Yichang can be seen.
The distribution area of the world's finless porpoise
So how to distinguish between these two finless porpoises? From the appearance, the most significant difference between the two is the dorsal ridge, although the dorsal ridge of the finless porpoise is not prominent, but the short man is tall, compared to the broad-ridged finless porpoise, the dorsal ridge of the narrow-ridge finless porpoise is more towering, and the dorsal ridge of the broad-ridge finless porpoise is more flat and rough; in addition, the back of the finless porpoise also has a wart grain protrusion, the number of warts of the broad-ridge finless porpoise is significantly different from that of the narrow-ridged finless porpoise, and the wart grains on the back of the broad-ridged finless porpoise can reach 10 to 14 columns, 48 to 120 mm wide; and the warty grain column of the narrow-ridge finless porpoise is less, 3~ About 12 mm, through these two features, basically as long as it is not too "outrageous" looking individuals, can be distinguished.
The upper part is the narrow-ridged finless porpoise and the lower part is the broad-ridged finless porpoise
The precarious "giant panda in the water"
With the declaration of functional extinction of the baiji dolphin, the Yangtze River finless porpoise may have become the only living cetacean in the Yangtze River, and in 2018, the Sino-US research team published the latest research results on the molecular biology of the Yangtze River finless porpoise, and found that the genes of the Yangtze River finless porpoise originally responded to the high-salt environment of the ocean have evolved, and in tens of millions of years, it has fully adapted to the low-permeability environment of fresh water, which means that reproductive isolation has appeared compared with the East Asian finless porpoise, so the research team believes that the Yangtze River finless porpoise should become an independent species. This also makes the significance of the Yangtze River finless porpoise more important.
However, since the 1990s, the number of Yangtze Porpoises has been in a rapid decline, and in 2006 the survey found that the number of populations in the main stream of the Yangtze River has been less than 1200, a decrease of more than 50% compared with the early 1990s.
The reason is that since the late last century, the ecological environment of the Yangtze River Basin has been deteriorating, resulting in different degrees of impact on various aquatic organisms living in it, and more importantly, it comes from the increasing intensity of human activities, according to the Yangtze River finless porpoise population decline mechanism study shows that due to the rapid development of the Yangtze River shipping industry, its man-made underwater noise to the juvenile finless porpoise has brought irreversible "hearing damage", although the Yangtze River finless porpoise can emit ultrasonic signals, but the gradual improvement of its sonar capacity also needs a process, during this period, Excessive underwater noise will make the juvenile sonar system underdeveloped or even unable to develop, and the juveniles without sonar ability lose contact with the female dolphin, and their viability is greatly reduced, that is, anthropogenic underwater noise may lead to a decrease in the birth rate of finless porpoise populations.
A risk assessment of the noise effects of the Yangtze River finless porpoise and other fish showed that about 1/3 of the underwater noise had a power spectrum higher than the hearing threshold of the Yangtze River finless porpoise
On the other hand, under the influence of factors such as barriers between rivers and lakes, overfishing and illegal fishing, the fish resources of the Yangtze River have declined sharply, and the bait available for the Yangtze River finless porpoise to prey is decreasing, thus affecting its quality of life.
Fishing boats on the Yangtze River
In order to protect the aquatic germplasm resources of the main stream and important tributaries of the Yangtze River, and at the same time alleviate the shortage of food for endangered organisms such as the Yangtze River finless porpoise and Chinese sturgeon, Cao Wenxuan, an academician of the Chinese Academy of Sciences, initiated the "ten-year fishing ban" plan for the Yangtze River in 2006, and 2021 is the opening year of the "ten-year fishing ban" of the Yangtze River, and after one year, as an important indicator of the health of the Freshwater ecosystem of the Yangtze River, the emergence of the Yangtze River finless porpoise in groups also shows that the aquatic ecological environment of the Yangtze River is developing steadily in a good direction.
References:
1.https://www.nature.com/articles/srep06572
2.https://www.nature.com/articles/s41467-018-03722-x
3.https://doi.org/10.1016/j.ecoenv.2021.112860
4.XU Pao, LIU Kai, XU Dongpo,et al. Conservation status and research prospect of Yangtze River finless porpoise[J]. Scientific Fish Farming, 2017(5):3.
5.Mei Zhigang, Hao Yujiang, Zheng Jinsong, et al. Research progress on the decline mechanism of Yangtze River finless porpoise population[J]. Life Sciences, 2011, 23(5):6.
6. Wang Jun,Li Hongzhi,Zuo Tao,Li Yongtao,Cheng Zhaolong,Yuan Wei,Niu Mingxiang. Research overview of marine finless porpoise[J].Advances in Fisheries Science,2021,42(05)
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