The fourth scientific expedition to the Yangtze finless porpoise was launched——
Find which "technical eyes" are used by "smiling angels"
◎Duan Bin reporter Jin Feng
At 7:30 on September 20th, the Yangtze River in early autumn was slightly cold, and the fine waves set off by the river wind soaked the clothes.
At Duan Yizheng Wharf in Yangzhou of the Yangtze River, two scientific research ships of China Fisheries Administration 031 and 038 have already brought supplies for a day and are ready to continue sailing.
On September 19, the 2022 Yangtze finless porpoise scientific expedition was officially launched.
This survey is the fourth scientific survey of finless porpoises in the entire Yangtze River basin after 2006, 2012 and 2017, and the first systematic survey of river basin species after the implementation of the 10-year fishing ban in the Yangtze River.
On the rear deck of the 038 scientific research ship, Wang Kexiong, a researcher at the Institute of Hydrobiology, Chinese Academy of Sciences, is leading a team to prepare scientific research equipment. In less than 10 minutes, everyone has taken their place according to the division of labor.
The Yangtze finless porpoise, known as the "smiling angel", is a national first-class protected wild animal in my country. It belongs to the unique freshwater cetaceans in the Yangtze River, and is also an important indicator species for evaluating the status of the Yangtze River ecosystem.
The scope of this scientific expedition includes about 1,600 kilometers in the middle and lower reaches of the main stream of the Yangtze River, Dongting Lake, Poyang Lake and some tributaries of the Yangtze River. More than 120 expedition team members and more than 20 fishery boats were carried out simultaneously.
What technological assistance was there in this scientific expedition?
Visual and automatic image-assisted investigation to capture the signal of finless porpoise on the water
Jiangsu is located in the middle and lower reaches of the Yangtze River. The water surface is wide and the wind and waves are large. The fishery administration ship used in this scientific expedition has been professionally transformed according to the actual situation, and a special observation platform has been built.
On the observation platform, three expedition team members are observing finless porpoises with binoculars. Each of them is wearing a life jacket with a safety rope tied to the back. Since the observation is from a boat, in order to reduce the influence of wind, waves and hull shaking, a simple wooden porpoise is placed under each binoculars. Support, 3 people are responsible for 3 different angles, and one person is responsible for data recording.
"Visual inspection is the core part of scientific investigation, and the sampling method is adopted." Chen Bingyao, a professor at Nanjing Normal University and an expert on cetaceans, told reporters, "due to the differences in the physical fitness and visual inspection range of each expedition team member, In order to maintain their energy, they rotate their positions every half an hour, and the replaced players should rest in time to replenish their energy. We have conducted professional training for all players before the exam.”
At the same time as the visual inspection, the automatic image assistance system in front of the inspection ship will also collect image data, and simultaneously record environmental information such as habitats, coastlines, and shipping along the Yangtze River.
The newly attempted automatic image assistance system, supplemented by artificial intelligence (AI) recognition in the later stage, can to a certain extent compensate for the error in population estimation due to the differences in the observation abilities of the team members, and help to objectively record and analyze the current status of the Yangtze finless porpoise population.
Passive acoustic monitoring and environmental DNA analysis technology to find underwater traces of finless porpoise
The above-water expeditions are carried out with the help of visual and automatic image assistance systems, while the underwater expeditions mainly use passive acoustic monitoring and environmental DNA analysis technologies.
Wang Kexiong and his colleagues put the sonar equipment into the river with a tow rope and introduced to the reporter: "The passive acoustic investigation is mainly to put the sonar system into the water. The sonar system consists of two parts, one is to judge by collecting signals. Whether there are finless porpoises in the surrounding waters, this part occupies less memory, but cannot receive sound waves in the whole process; another part is continuously collecting sound waves, which can form a one-day waveform record; the combination of the two parts can effectively determine the distribution and number of finless porpoises.”
On the 031 scientific research ship, Zheng Jinsong, a researcher from the Institute of Hydrobiology, Chinese Academy of Sciences, is using a water collector to collect water samples. He introduced that environmental DNA analysis technology is an emerging species monitoring method. Sampling to obtain information on the species of aquatic organisms remaining in the water samples.
Based on the information on the distribution and relative density of finless porpoises in different waters, it is helpful to supplement the distribution information of the Yangtze River finless porpoises with very few distributions.
"Scientific research 038, I am 031, please report the water depth and speed."
"038 received, the water depth is 16 meters, 300 meters from the shore, and the speed is 14.8 kilometers per hour."
"Please keep the current speed and keep going."
During the expedition, similar calls between 031 and 038 continued.
Chen Bingyao introduced that the visual inspection method requires that the departure time of the two ships is about half an hour before and after, or 5 kilometers apart, to avoid mutual interference and double counting in observation, and the speed of the ship should be kept at 14-15 kilometers per hour.
The scientific research ships ensure the consistency of methods and methods by reminding each other.
As the scientific research ship continued to move, Wang Kexiong sighed: "This scientific expedition is much better than the previous several times. On the one hand, the ecological environment on both sides of the Yangtze River has been significantly improved; on the other hand, thanks to the ten-year ban on fishing in the Yangtze River, the past During the scientific expedition, there were many fishing boats on the river, and there were nets under the water. The scientific expedition boats often had difficulty in passing, but now they are unimpeded, which has greatly improved the efficiency of scientific expeditions."