Our reporter Wang Ziqiang and Zhang Liyun
"Bell! Bell!" At 6:30 in the morning, two rapid alarm bells awakened the scientific expedition team members in their sleep. From the deck exclaimed: "A large group of tropical spotted dolphins! Estimated to exceed 100!"
Freund's dolphins photographed in a certain area of the South China Sea on July 20. Photo by Xinhua News Agency reporter Zhang Liyun
Everyone quickly climbed out of the bed and ran directly to the second floor despite the greasy faces. They saw groups of dolphins surrounded by three or four meters on both sides of the ship's gunner of the "Tianlong" scientific research ship, swinging its tail fin up and down to move forward, and row out on the sea. An arc.
The team’s chief scientist Li Songhai corrected: “This is not a tropical spotted dolphin, it is a long-nosed spinning dolphin.” The team member on the side said as they noted, “Long-nosed spinning dolphin, at 6:20, GPS position 46.”
This is the 9th day of whale hunting at sea.
Ask the whale
Cetaceans are the collective term for all animals belonging to the Chordodactyla, Euzodia, and Cetaceans, and are divided into toothed whales and baleen whales. In people’s customary descriptions, there are often several names for different cetaceans: whales, dolphins and porpoises (including finless porpoise).
In the 1950s, my country did not ban whaling. Scholar Wang Pilie went to sea with the whaling ship and collected some information on cetaceans in the South China Sea north of Hainan Island and included them in "Chinese Whales" and "Chinese Sea Beasts Illustrated Book."
In 1981, China completely stopped whaling activities. Since it was very expensive to organize cetacean scientific expeditions separately, and the basic research awareness at that time was not strong, the research on offshore cetaceans in my country has since stagnated, and the research on cetaceans in the South China Sea is almost blank.
“The South China Sea occupies two thirds of the total area of China’s territorial waters. It is necessary to fully understand its biological resources, especially rare animal resources. Cetaceans are the objects of animal protection of global concern, and are the flagship animals and indicative creatures of the marine ecosystem. Irreplaceable research and protection value.” At the end of 2012, Li Songhai, who had been engaged in marine mammal research abroad for many years, returned to Hainan to continue his research on cetaceans and other marine mammals at the Deep Sea Institute of the Chinese Academy of Sciences.
Lingtou Town, Changhua Town, Meilian Village... The following year, Li Songhai and his colleagues traveled to coastal fishing villages on Hainan Island and distributed more than 500 questionnaires to fishermen to investigate cetacean tracks.
The results are exciting: the fishermen not only confirmed that they have witnessed a variety of cetaceans at sea, but also identified the Chinese white dolphins with a special body color in the illustrated book! The following year, the scientific expedition team found the first-class national protected animal from the east to the coast of Sanya.
"The Chinese white dolphin is a near-shore cetacean species. The water depth of the sea area that lives in is often within 30 meters and the distance from the shore is no more than 30 kilometers. There are such a group of rare and endangered animals in the southwestern coast of Hainan Island. The attention and knowledge of cetaceans are still very limited." Li Songhai said with some regret.
In 2016, the Deep Sea Institute established the “Professional Database of Cetacean Stranding Records in Hainan Island”. Based on the information collected through the database, combined with previous visits to fishermen, Li Songhai judged that the South China Sea is likely to live in abundance of deep diving and pelagic cetaceans.
Speculation is not enough. Li Songhai said that some cetaceans have very little differences, and fishermen can't distinguish them; the database can only count the types of stranded animals, but they don't know where they come from. To scientifically evaluate the species diversity and distribution of cetaceans in the South China Sea, it is necessary to conduct field investigations.
In April last year, the "2019 South China Sea Deep Diving and Offshore Cetacean Scientific Research" organized by the Marine Mammal and Marine Bioacoustics Laboratory of the Deep Sea Institute set sail, and Li Songhai served as the chief scientist of the voyage. This is the world's first deep-diving and high-sea cetacean scientific expedition in the corresponding waters of the South China Sea. This voyage recorded a total of 8 cetacean species including sperm whales, Koroti's beaked whales, and short-leg pilot whales. For the first time, it was confirmed that sperm whales, Koroti's beaked whales, short-legged pilot whales and other cetaceans exist in the corresponding waters of the South China Sea.
On July 8 this year, the team set off again. The survey area is concentrated on the land slopes, seamounts and trough waters of the Paracel Islands and Zhongsha Islands in the northern part of the South China Sea. The scope is wider than the previous time, and the survey content and methods used are more diverse.
This year's scientific examination team consists of 15 people, of which 7 are "post-95" graduate students. The youngest member is only 21 years old and just graduated from undergraduate a few weeks ago. Some students already have rich marine scientific research experience. According to a student, he studied in the Fisheries College of Undergraduate and often went to sea with fishing boats. "The fishing boat is very small, the boat is full of oil and fishy smell, very uncomfortable. This is the best boat I have ever followed."
This "best ship" has a displacement of only 450 tons and has been in the water for 10 years. Except for the female team members and some researchers, the other 8 team members lived with the crew in the large cabin. The large cabin has only three circular windows with a diameter of 40 cm, which is dark and damp; sleeping on a 0.6-meter-wide wooden bed must be careful when turning over.
According to the "Normalized Epidemic Prevention and Control Plan" formulated before sailing, everyone must take their body temperature and fill out a health registration form before work every day. One of them is "Physical condition of the day". There are 4 options, namely A "normal", B "slightly discomfort", C "discomfort" and D "unable to work".
3 A, 7 B, 4 C, 1 D, this is the physical record of the whole team on the first day of going to sea. The boat sailed from Sanya to the target sea area, the boat was small and the waves were big, the crew could not adapt for a while, and the seasickness was serious.
The conditions are difficult, and the young team members hope to see the cetaceans as soon as possible to motivate themselves to complete the next voyage.
After 5 days, the team members basically adjusted to life on board, and their appetites improved. The voyage leader and senior engineer Dai Liang joked at the regular meeting that everyone felt that everyone had entered the "enjoyment period" from the "distress period", and the team members smiled approvingly.
——But on land, such "enjoyment" is just normal life.
This scientific expedition includes visual observation, acoustic monitoring, marine floating garbage recording, and water sample collection and analysis. Among them, the use of visual means to discover, track and record cetaceans is both the center and the basis of all work.
It may be different from the outside world's imagination: the main reliance on finding cetaceans is actually human eyes and telescopes. Especially last year, the team did not use any equipment, relying solely on the naked eye, and witnessed 27 groups of whales within 14 days.
Whales are mammals and they breathe with their lungs. When exhaling, the breathing hole will eject a column of air. Toothed whales have a breathing hole and baleen whales have a pair. The difference in morphology makes the shape of the air column of different cetaceans different, and also provides an entry point for the identification of species. Most of the time, animals are far away from the ship and cannot be directly observed. Waves and air columns are the focus of search.
From 8 am to 7 pm, the team members took turns standing on the top of the cockpit to search visually. Although it is a collective shift, there are too few people. The team members work in shifts about 3 times a day, and each time is an uninterrupted hour and a half. In this vast expanse of tropical ocean, as soon as the sun comes out, the temperature is over 30 degrees Celsius. The sun was unshielded, so hot that people couldn't open their eyes; the ship was soaked in heavy air, and the surface of the hull became damp and astringent. If you touched it casually, the hands were full of coarse salt crystals.
No matter what you do outside the cabin, you must wear sun protection clothes, sun hats and sunglasses. One of the team members did not wear a sun hat and worked on the rear deck for less than half an hour. The next day, his face became flushed and his skin began to peel. Sun protection clothing is poorly ventilated. People only stand on the deck for more than ten minutes, and their backs are as if water has been poured. The clothes are soaked in sweat and translucent, and they are wrinkled on the body. The salt drinks on the ship are consumed quickly, sometimes two boxes a day.
Visual inspection not only challenges the body's ability to withstand, but also tests patience. Although the seas searched by the scientific expedition team are theoretically rich in cetacean species diversity, it is not easy to find them. The visual team members found the animal, and the crew rang a short bell to remind them that the animal had disappeared before the others boarded the roof—similar things had happened many times.
11 hours of visual observation a day, the best record, but short bells were heard 3 times a day. Most of the time, as far as one can see, it is either the billowing sea or the white clouds spreading to the skyline. Most of the time during the whale hunt is boring.
Listen to the whale
"Report to the visual group, a strong animal signal is received." The voice of the acoustic group came from the intercom. Compared with last year, looking for whales this year is no longer just watching with eyes, but also listening with "ears."
According to Dong Lijun, head of the acoustics group and assistant researcher of the Deep Sea Institute, sound is the most effective way of energy transmission underwater. In order to adapt to the aquatic environment, cetaceans and other marine mammals have developed highly developed vocal and auditory abilities during the long-term evolution. Most of them frequently emit species-specific sounds underwater to communicate and communicate between individuals or groups.
The sound frequencies of different cetaceans are different. The peak frequency of high-frequency echolocation signals of porpoises (including finless porpoises) can reach 120-130 kHz, while that of tropical spotted dolphins is around 90 kHz, while the range of human hearing is 20 Hz to 20 kHz, which cannot be heard directly. Such sounds of whales. The acoustic team uses instruments to monitor animal vocalization activities: during the day, towed hydrophones are used to monitor in real time, looking for animal "traces" to help the visual team find animals faster; at night, self-contained acoustic recorders are used to collect and store all directions Various sound data for subsequent animal acoustic behavior research, and through the hydrophone array, to study the animal’s high-frequency echolocation signal characteristics.
Although it is called the "Acoustic Group", their work is also "expensive." The visual group stared at the sea, and the acoustic group stared at the spectrogram on the computer screen, combined with known animal acoustic behavior characteristics, to determine whether there were animals infested. The vertical axis range of the spectrogram is as high as 96 kHz. Sometimes the low-frequency acoustic signal of animals is only between 2-3 kHz, which almost coincides with the background noise where the main sound energy is concentrated in 1-2 kHz. If you don’t concentrate , It’s easy to miss animals because of neglect.
Dong Lijun had been staring at the screen for 2 hours. When changing shifts, his eyes were sore and swollen, and tears continued.
Because of lack of experience, the acoustic team has also made detours. At the end of the first day of work, a member excitedly said that he had found the signal of a sperm whale. In the next few days, the signals of suspected sperm whales have also been on, continuous and regular. Strangely, the signal disappeared when the ship stopped; when the ship started, the signal appeared again. Dong Lijun inferred that this is the sound of the engine: the acoustic characteristics of the noise produced by the engine under water, on the spectrogram, are similar to the sperm whale signal.
During this voyage, more than half of the whales were first "heard" by the acoustic team and then confirmed by the visual team.
"Sperm whale! It's a sperm whale!" At noon on July 24, Li Songhai looked through his binoculars and found several iconic air pillars in the distance. Due to the special location of the breathing holes, the air pillars of sperm whales are always breathing when they surface. It sprays to the front left at a 45-degree angle.
At this time, the sperm whale was found, and the whole team was shaken: the voyage was about to end in 5 days. The team members discovered nearly 10 species of cetaceans, but still did not see the sperm whale. The Deep Sea Institute team discovered this species in the South China Sea last year, and this year has great expectations for another sighting.
Sperm whales are the largest toothed whales. They are a typical deep-diving animal. They are widely distributed in non-icing waters around the world. They can be found from the equator to the poles. They have special ecological and protection value. Historically, sperm whales have been regarded as important targets for hunting because of the widespread use of whale oil on their heads.
On the endless sea, a series of air columns sprayed out one by one, with an interval of only two or three seconds. Li Songhai was not sure: "With so many air columns, it may not be a sperm whale, but the possibility is still great! Even if it is not a sperm whale, it must be a big one, definitely not a dolphin!"
When the boat got closer, I saw a few dozen-meter-long animals swimming slowly on the sea, like a few huge driftwoods; their huge heads were square, accounting for almost one-third of the body length. "You can't go wrong, it's the sperm whale! Hurry up and let everyone know!"
Hearing that there was a sperm whale, the team members put down their dishes and rushed to the top of the cabin. Binoculars, cameras, mobile phones... all kinds of equipment that can bring the distance closer, the team members have used them. "Ah! It's a sperm whale!" "Let me see, my camera's focal length is not enough!" "It's really big! There are patterns on my body!" Everyone was excited and nervous.
"Captain, the speed of the boat is slower, don't scare them." While observing, Li Songhai used the walkie-talkie to give orders. After the animals are found, if conditions permit, a small boat can be set up to observe and take pictures at close range, and the acoustic team members can collect animal sounds.
"The animals did not avoid the boat, they are ready to put the boat!" A boat carrying 6 people split the waves and gradually approached the group of whales. The boat is 9 meters long, which is significantly shorter than the sperm whale. Judging from the big boat, these "big guys" don't seem to move much, but the boats are very strenuous to follow them. It took more than 20 minutes to get close to them.
"Report the big ship, there are 7 in total, of which 1 is a larva! They are molting!"
Sperm whale molting is part of the natural antifouling mechanism, and the shed skin can be used for gene sequencing, which is a very rare research material. The players are undoubtedly lucky.
"This animal is difficult to judge." "Is it a baby killer whale or a melon-headed whale?" "Look at its mouth! There is a white border, it is a typical baby killer whale!" The scientific expedition team searched for animals and took pictures during the day. Get together in the evening to identify the species found.
This is no easy task: individual size, dorsal fin shape, shape, and behavioral characteristics are all factors to be referred to. Some species have very small differences, and if they miss key features when taking pictures, they cannot be identified. For example, the biggest difference between the long-nosed spinning dolphin and the long-nosed true dolphin is that the latter has a white spot in the center of the dorsal fin; the biggest difference between the pseudo orcas and the baby killer whale is the difference in size, the latter is small in size and the snout is white.
In addition to visual recognition, once a cetacean is found, members of the Environmental DNA (eDNA) group will take a sample of the sea surface water from the gunwale. According to Li Jianlong, the head of the eDNA group and a teacher at the School of Oceanography of Hainan University, the use of vacuum filtration pumps can enrich the DNA in the water sample on the filter membrane, and then use DNA sequencing to identify and confirm cetaceans from the perspective of molecular biology. Types and distribution of animals.
The scientific expedition lasted 21 days with a voyage of more than 3,000 kilometers. The investigation witnessed 31 groups and 11 species of deep-diving and pelagic cetaceans, of which 14 groups and 7 species of deep-diving cetaceans were sperm whales, corkscrew's beaked whales, short-limbed pilot whales, and Wright's dolphins (also Flower whales), pseudo killer whales, baby killer whales and melon-headed whales; 4 other pelagic cetaceans are tropical spotted dolphin, Freund's dolphin, long-nosed spinning dolphin and striped dolphin. Compared with last year, the scientific expedition newly discovered and recorded four cetacean species including baby killer whales, pseudo killer whales, long-nosed spinning dolphins, and melon head whales, indicating that the surveyed waters have relatively rich cetacean species diversity.
Many "mother-child pairs" were also discovered during the scientific expedition. Li Songhai introduced that whales are a highly socialized marine animal, and the social form of many cetaceans is similar to a "maternal society." The discovery of "mother-child pair" indicates that the South China Sea is likely to be the settlement place for these cetaceans.
"Marine animals, marine environment and marine ecological protection are hot topics in current international multilateral exchanges and global environmental governance. Research and protect the marine ecological environment and biological resources of the South China Sea, especially cetaceans and other rare and endangered marine animals Resources. Carrying out a survey of cetacean resources in the South China Sea is of great significance both from the perspective of scientific research and protection." Li Songhai said.