Method for reconstructing life history of Yangtze River main stream-Poyang Lake based on dentin Sr isotope ratio

Abstract

The invention discloses a method for reconstructing the life resume of Yangtze River main stream-Poyang Lake based on a dentin Sr isotope ratio. The method comprises the following steps: collecting a tooth sample; cleaning the teeth; slicing the teeth; analyzing the 87Sr / 86Sr ratio sequence of the dentin; tooth growth layer group measurement and life history reconstruction. According to the method, the direct relation between the tooth dentin 87Sr / 86Sr ratio and the habitat 87Sr / 86Sr ratio is utilized, and the dentin 87Sr / 86Sr ratio is used as the agency of the cowfish habitat inversion. In-situ laser ablation analysis is adopted, the speed is high, the result accuracy rate is high, and the resolution ratio is high (0.25 micron level); moreover, the age information and the habitat information can be combined, the lifelong 87Sr / 86Sr ratio fluctuation condition can be provided, and the lifelong life history and migration condition of dead cowfish individuals can be traced.

Description

Technical Field

[0001] The present invention belongs to the field of ecological technology, and specifically relates to a method for reconstructing the life history of Yangtze finless porpoises in the Yangtze River mainstream-Poyang Lake based on dentin Sr isotope ratios. Background Art

[0002] The Yangtze River dolphin is a small freshwater toothed whale unique to my country. It mainly lives in the middle and lower reaches of the Yangtze River, Dongting Lake and Poyang Lake, and the tail of its tributaries. The Yangtze River dolphin is currently the only cetacean in the Yangtze River and has become an important indicator species reflecting the health of the Yangtze River ecosystem. With the continuous economic and social development of the Yangtze River Basin, human water activities have continued to intensify, the structure and function of the aquatic ecosystem have undergone drastic changes, and the Yangtze River dolphin population has declined rapidly. In 2022, the Ministry of Agriculture and Rural Affairs organized a scientific survey of Yangtze River dolphins in the entire basin. The results showed that the population of Yangtze River dolphins was 1,249, including about 595 in the mainstream of the Yangtze River, about 492 in Poyang Lake, and about 162 in Dongting Lake. Compared with 2017, there has been a historic rebound, but the population of Yangtze River dolphins is still small, the critically endangered status has not changed, and the protection situation remains severe.

[0003] A large number of studies have shown that Yangtze finless porpoises have an adaptive migration rhythm between the Yangtze River mainstream and Poyang Lake as the hydrological situation changes. In the 1990s, based on the seasonal changes in distribution frequency, researchers proposed that Yangtze finless porpoises frequently migrated between Poyang Lake and the Yangtze River mainstream. In recent years, with the rapid decline in the number of Yangtze finless porpoises and the intensification of human disturbances such as the cross-lake bridge and shipping development in the Poyang Lake estuary area, the migration of Yangtze finless porpoises has been greatly restricted, and the scale of migration has been significantly reduced. Based on visual observations and fixed-point acoustic monitoring, it is speculated that there is still seasonal "river and lake" migration, but on a small scale. Determining the habitat selection of Yangtze finless porpoises and their migration activities between different habitats is an important basis for carrying out rescue protection of Yangtze finless porpoises. However, due to the lack of typical features such as appearance and body color that can be used for individual identification of Yangtze finless porpoises, acoustic technology has not yet been able to establish the soundprint characteristics for identifying individual Yangtze finless porpoises. Therefore, we can only rely on visual observation to identify the up-and-down events and migration numbers of Yangtze finless porpoises, and the spatial differences in the intensity of Yangtze finless porpoise activity at each point of the acoustic monitoring array to identify the up-and-down events and migration numbers of Yangtze finless porpoises. However, since visual observation cannot achieve continuous tracking observation and passive acoustic technology cannot yet achieve voiceprint recognition, it is impossible to accurately identify the migration events and migration scale of Yangtze finless porpoises. In addition, since Poyang Lake is naturally connected to the mainstream of the Yangtze River, there is a possibility that the Yangtze finless porpoises that died in Poyang Lake drifted downstream into the mainstream of the Yangtze River. This obviously interferes with accurately grasping the source of the dead Yangtze finless porpoises, scientifically identifying the ecological risks of their native habitats, and supporting the protection and restoration of the Yangtze finless porpoise habitat.

[0004] Therefore, in order to understand the events and scale of Yangtze finless porpoise migration, trace the dead individuals in Poyang Lake, and support the protection and management of Yangtze finless porpoises in Poyang Lake and adjacent waters as well as population development assessment, it is urgent to invent a method that can accurately identify whether Yangtze finless porpoise individuals have migrated from the "Yangtze River main stream to Poyang Lake". Summary of the invention

[0005] Technical problems solved: In response to the above technical problems, the present invention provides a method for reconstructing the life history of Yangtze River porpoises in the Yangtze River mainstream-Poyang Lake based on the Sr isotope ratio of dentin, which can effectively solve the problem of the difficulty in tracing the dead Yangtze River porpoises. In toothed whales, only one set of teeth (monophyodonty) grows in a lifetime: congenital dentin develops in the uterus, and its analysis can provide rare materials for understanding the physiological processes occurring during pregnancy; the neonatal line formed after birth marks the beginning of metagenic dentin deposition, and then the pulp cavity is gradually filled with alternating wide and narrow bands of dentin growth layer groups (growthlayer groups, GLGs). Dentin is a metabolically inert mineralized tissue, mainly composed of inorganic mineral components (hydroxyapatite), and it hardly changes after deposition, thereby recording the trace elements and isotope information of the habitat of the individual throughout his life, and using GLG as a marker and recording with annual resolution. Therefore, teeth provide excellent experimental materials for reconstructing the life history of Yangtze River porpoises based on Sr isotope technology.

[0006] During the formation of biomaterials, Sr isotopes ( 87 Sr / 86 Sr ratio) is almost not fractionated and will not be affected by factors such as its diet change, growth and development, which directly reflects its source. 87 Sr / 86 Sr ratio, so the dentin analyzed along the growth axis from the cusp to the pulp cavity 87 Sr / 86 Sr can represent the habitat experienced by animals. 87 Sr / 86 A direct and complete record of Sr. in freshwater environments 87 Sr / 86 The Sr ratio is mainly affected by the geological factors of the basin and remains basically stable in different years. 87 Sr / 86 The Sr ratio is between 0.710 and 0.711. 87 Sr / 86 The Sr ratio is between 0.713 and 0.716. 87 Sr / 86 There are significant differences in Sr ratio. In summary, according to the87 Sr / 86 The Sr ratio was used to determine the habitat of Yangtze finless porpoises before their death. 87 Sr / 86 The Sr ratio between 0.713 and 0.716 corresponds to the life history of Poyang Lake. 87 Sr / 86 The Sr ratio of 0.710-0.711 corresponds to the freshwater life history of the middle and lower reaches of the Yangtze River. 87 Sr / 86 Sr ratio analysis can not only determine whether an individual has a migration history from the Yangtze River to Poyang Lake, but also determine the area where the deceased individual lived before death, thus providing a new solution to the problem of tracing the origin of deceased Yangtze River porpoises.

[0007] Technical solution: A method for reconstructing the life history of Yangtze River porpoises in the Yangtze River mainstream-Poyang Lake based on the Sr isotope ratio of dentin, comprising the following steps: Step 1) Tooth sample collection: Collect teeth from dead Yangtze finless porpoises found in the middle and lower reaches of the Yangtze River and Poyang Lake. Select the larger and straighter teeth in the middle of the left and right rows of the lower jaw. For individuals with severe tooth decay and missing teeth, select relatively suitable parts from the available teeth for analysis. Step 2) Teeth cleaning: Use a toothbrush to remove the attached tissue on the outside of the extracted tooth, use pointed tweezers to pick out the tissue inside the pulp cavity, rinse it with clean water, and then use deionized water to clean the outside and inside of the tooth; Step 3) Tooth sectioning: embed the tooth in resin and use a precision cutter to cut along both sides of the maximum growth axis from the cusp to the root parallel to the coronal plane, so that the maximum growth axis remains on the slice, grind and polish the slice from both sides, and ultrasonically clean it with deionized water; Step 4) Dentin 87 Sr / 86 Sr ratio sequence analysis: Laser ablation coupled with multi-collector inductively coupled plasma mass spectrometry was used to perform line scanning analysis from the cusp along the dentin growth layer group to the pulp cavity to obtain the dentin 87 Sr / 86 Sr ratio series; dentin 87 Sr / 86 The raw data of the Sr ratio series were analyzed using a generalized additive model to obtain a smooth curve after fitting, which minimized the background noise while maintaining the important changes in the data; Step 5) Measurement of tooth growth layer groups: After laser ablation, the surface of the slice is photographed using a metallographic microscope, and the distance between each dentin growth layer group is measured along the laser ablation line to assist in interpretation 87 Sr / 86 The relationship between the Sr ratio series and the age of Yangtze finless porpoises; Step 6) Reconstruction of life history: Based on teeth 87 Sr / 86 The Sr ratio and its tooth growth age are determined by the water environment. 87 Sr / 86 The Sr ratio can be used to determine the habitat of the animal at that time.

[0008] Preferably, in step 4), the RESOlution SE 193nm laser ablation system is used to perform micro-area in-situ analysis of the dentin of the tooth, and the ablation is continuously performed from the junction of the enamel and the dentin along the dentin growth layer group to the pulp cavity; the ablated aerosol enters the connected multi-receiver inductively coupled plasma mass spectrometer for analysis to obtain the dentin 87 Sr / 86 Sr ratio sequence; the analysis uses glass standard NIST SRM 610 to debug the instrument status, and the apatite standard Durango monitors the instrument during sample analysis 87 Sr / 86 The accuracy and repeatability of the Sr ratio; the laser line scanning speed is 5 μm / s, and the integration time of the laser ablation connected multi-collector inductively coupled plasma mass spectrometer is 0.5 s, that is, data within 0.25 μm on the laser beam spot forward path will be acquired every 0.5 seconds.

[0009] Preferably, in step 4), during the processing of the instrument raw data, the "on peak zero" method is used to deduct the interference of Kr, and the monitoring 85 Rb signal is deducted 87 Rb 87 The interference of Sr, according to 88 Sr / 86 The isotopic abundance ratio of Sr in nature is 8.375209. The mass fractionation factor is calculated using the exponential law. 87 Sr / 86 The Sr ratio was used for instrument mass fractionation correction. Finally, the interference correction and mass fractionation correction were obtained. 87 Sr / 86 Sr measurements were performed using the mgcv package in the statistical software R. 87 Sr / 86 The Sr ratio data was smoothed and visualized using ggplot2.

[0010] Preferably, in step 5), after laser ablation, a metallographic microscope is used to photograph the slice surface, and the distance between the light band and the dark band of each adjacent dentin growth layer group is measured along the laser ablation line; 87 Sr / 86The positions of the light and dark bands of each dentin growth layer group were marked on the smoothed data of Sr ratio to read the animal age. 87 Sr / 86 The Sr ratios correspond to the life stages of dentin formation, interpreting the habitat changes at different life stages.

[0011] Preferably, in step 6), the dentin 87 Sr / 86 The fluctuation curve of Sr ratio and its tooth growth age are determined by water environment. 87 Sr / 86 The Sr ratio can be used to identify the habitats of Yangtze finless porpoises of different age groups, thereby reconstructing the life history of Yangtze finless porpoises; 87 Sr / 86 The Sr ratio range is 0.710-0.711; 87 Sr / 86 The Sr ratio range is 0.713-0.716. Therefore, the main stream of the middle and lower reaches of the Yangtze River and the water body of Poyang Lake 87 Sr / 86 There are significant differences in Sr ratio. In summary, according to the 87 Sr / 86 The Sr ratio was used to determine the habitat background of the dead finless porpoises. 87 Sr / 86 The Sr ratio between 0.713 and 0.716 corresponds to the life history of Poyang Lake. 87 Sr / 86 The Sr ratio of 0.710-0.711 corresponds to the freshwater life history of the Yangtze River mainstream.

[0012] Beneficial effect: The present invention utilizes tooth dentin 87 Sr / 86 Sr ratio and habitat 87 Sr / 86 Direct relationship between Sr ratio and dentin 87 Sr / 86 The Sr ratio is used as a proxy for the inversion of the finless porpoise's habitat. In-situ laser ablation analysis is fast, has high accuracy, and high resolution (0.25 μm level); it can also combine age information with habitat information, providing a lifetime 87 Sr / 86 The fluctuation of Sr ratio was used to trace the life history and migration of dead finless porpoises. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1-2 The tooth of a dead finless porpoise found in the lower reaches of the Yangtze River is from the junction of enamel and dentin to the pulp cavity. 87 Sr / 86 Sr ratio, 87 Sr / 86 The Sr ratio did not change significantly, indicating that it lived in the Yangtze River; Figure 3-4 The tooth of a dead finless porpoise found in Poyang Lake is from the junction of enamel and dentin to the pulp cavity. 87 Sr / 86 Sr ratio, 87 Sr / 86 The Sr ratio did not change significantly, indicating that it lived in Poyang Lake; Figure 5 The tooth of a dead finless porpoise found in the lower reaches of the Yangtze River is from the junction of enamel and dentin to the pulp cavity. 87 Sr / 86 Sr ratio, the pig teeth 87 Sr / 86 The Sr ratio has significant changes, indicating that it has migrated between Poyang Lake and the Yangtze River; The light green background is Poyang Lake. 87 Sr / 86 Sr ratio range, the light purple background is the Yangtze River 87 Sr / 86 Sr ratio range, light red is ocean 87 Sr / 86 Sr ratio. The black solid line is the dentin based on GAM analysis 87 Sr / 86 Sr ratio fitting value, gray interval is 95% Bayesian confidence interval. DETAILED DESCRIPTION

[0014] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments: Example 1

[0015] (1) Collecting tooth samples from dead finless porpoises: Collect teeth from dead finless porpoises found in the middle and lower reaches of the Yangtze River and Poyang Lake. Select the larger and straighter teeth in the middle of the left and right rows of the lower jaw. For individuals with severely decayed and missing teeth, select relatively suitable parts from the available teeth for analysis.

[0016] (2) Tooth cleaning: Use a toothbrush to clean the extracted tooth to remove the attached tissue on the outside of the tooth, use pointed tweezers to pick out the tissue inside the pulp cavity, rinse it with clean water, and then use deionized water to clean the outside and inside of the tooth 6 times.

[0017] (3) Tooth sectioning: The cleaned and dried teeth were embedded in cold mounting resin. After the resin solidified, a cutter (Buehler Ltd., Evanston, USA) was used to cut the teeth parallel to the coronal plane along the maximum growth axis from the cusp to the root, so that the maximum growth axis remained on the slice. The slices were ground from both sides using 1200-mesh, 2400-mesh, and 4000-mesh sandpaper (Struers, Copenhagen, Denmark) in sequence. Then, the slices were polished on a polishing cloth (Struers, Copenhagen, Denmark) using a silica suspension to make the tooth slices more transparent and facilitate the observation of the dentin growth layer group. The slices were then ultrasonically cleaned with deionized water for laser ablation.

[0018] (4) Dentin 87 Sr / 86 Sr ratio sequence analysis: Using laser ablation coupled to multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) technology, the RESOlution SE193nm laser ablation system (AustralianScientific Instruments, ACT, Australia) was used to perform micro-area in situ analysis of the dentin of the teeth, starting from the confluence of the enamel and dentin along the dentin growth layer group (GLG) to the pulp cavity. The ablated material was taken out of the sample cell with high-purity He as the carrier gas, mixed with high-purity Ar and N2, and then entered the connected Neptune plus multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS) (Thermo Scientific, Dreieich, Germany) for analysis to obtain the dentin 87 Sr / 86 Sr ratio sequence. The laser line scan speed is 5 μm / s, and the MC-ICP-MS integration time is 0.5s, that is, data within 0.25 μm on the laser beam spot path is acquired every 0.5 seconds, with high spatial resolution. The analysis uses glass standard NIST SRM 610 to debug the instrument status, and apatite standard Durango and shark teeth (shark teeth 87 Sr / 86 Sr ratio and global ocean 87 Sr / 86 The same Sr ratio) was used as apatite reference sample. The standard sample was tested every 20 minutes before and during the test. 87 Sr / 86The accuracy and repeatability of the Sr ratio. MC-ICP-MS receives a blank of about 20 seconds before analysis, and uses its average value as the background value to deduct the background interference in the subsequent data processing; In the process of instrument raw data processing, the "on peak zero" method is used to remove the interference of Kr and monitor 85 Rb signal is deducted 87 Rb 87 The interference of Sr, according to 88 Sr / 86 The isotopic abundance ratio of Sr in nature is 8.375209. The mass fractionation factor is calculated using the exponential law. 87 Sr / 86 The Sr ratio was used for instrument mass fractionation correction. Finally, the interference correction and mass fractionation correction were obtained. 87 Sr / 86 Sr measured values. The generalized additive model (GAM) analysis was performed using the mgcv package in the programming statistical software R to obtain 87 Sr / 86 The Sr ratio is fitted with a smooth curve, which minimizes noise while maintaining important changes in the data; the smoothed data is visualized using ggplot2.

[0019] (5) Measurement of tooth growth layer groups: After laser ablation, the slice surface was photographed using a DM2700 M metallographic microscope (Leica, Solms, Germany), and the distance between the light and dark bands of each adjacent dentin growth layer group was measured along the laser ablation line. 87 Sr / 86 The positions of the light and dark bands of each dentin growth layer group were marked on the smoothed data of Sr ratio to read the animal age. 87 Sr / 86 The Sr ratios correspond to the life stages of dentin formation, interpreting the habitat changes at different life stages.

[0020] (6) Life history reconstruction: based on dentin 87 Sr / 86 The fluctuation curve of Sr ratio and its relationship with the tooth growth period (year, season) and water environment 87 Sr / 86 The Sr ratio can be used to infer the habitat types of Yangtze finless porpoises in different age groups, thereby inferring the life history of Yangtze finless porpoises. 87 Sr / 86 The Sr ratio is between 0.710 and 0.711; 87 Sr / 86The Sr ratio is between 0.713 and 0.716. Therefore, Poyang Lake and the middle and lower reaches of the Yangtze River have 87 Sr / 86 The significant difference in Sr ratio can be summarized based on the 87 Sr / 86 The Sr ratio can be used to determine the habitats where the finless porpoises have lived. 87 Sr / 86 The Sr ratio between 0.713 and 0.716 corresponds to the life history in the Poyang Lake habitat. 87 Sr / 86 The Sr ratio of 0.710-0.711 corresponds to the freshwater life history of the Yangtze River.

[0021] like Figure 1-Figure 2 Shown are teeth of dead finless porpoises found along the lower reaches of the Yangtze River 87 Sr / 86 The Sr ratio did not vary much, and was basically in the range of 0.710-0.711. This result is close to the measured value of water samples in the lower reaches of the Yangtze River, indicating that the life history of these Yangtze River porpoises is basically in the lower reaches of the Yangtze River. 87 Sr / 86 The stability of Sr ratio. Figure 3-Figure 4 Shown are teeth of a dead finless porpoise found in Poyang Lake 87 Sr / 86 The Sr ratio did not vary much, generally between 0.713 and 0.716, which was consistent with the measured values ​​of Poyang Lake water samples, indicating that these finless porpoises mainly lived in Poyang Lake during their growth period. Figure 5 Shown are teeth of dead finless porpoises collected along the lower reaches of the Yangtze River 87 Sr / 86 The Sr ratio changed dramatically from 0.710-0.711 to 0.713-0.716 and then to 0.710-0.711. This result shows that this Yangtze finless porpoise changed its habitat from the Yangtze River to Poyang Lake during its growth period. After living in Poyang Lake for a long period of time, it left Poyang Lake and went to the mainstream of the Yangtze River.

[0022] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for reconstructing the life history of Yangtze River porpoises in the Yangtze River mainstream-Poyang Lake based on dentin Sr isotope ratios, characterized in that: The following steps are involved: Step 1) Tooth sample collection: Collect teeth from dead Yangtze finless porpoises found in the middle and lower reaches of the Yangtze River and Poyang Lake. Select the larger and straighter teeth in the middle of the left and right rows of the lower jaw. For individuals with severe tooth decay and missing teeth, select relatively suitable parts from the available teeth for analysis. Step 2) Teeth cleaning: Use a toothbrush to remove the attached tissue on the outside of the extracted tooth, use pointed tweezers to pick out the tissue inside the pulp cavity, rinse it with clean water, and then use deionized water to clean the outside and inside of the tooth; Step 3) Tooth sectioning: embed the tooth in resin and use a precision cutter to cut along both sides of the maximum growth axis from the cusp to the root parallel to the coronal plane, so that the maximum growth axis remains on the slice, grind and polish the slice from both sides, and ultrasonically clean it with deionized water; Step 4) Dentin 87 Sr / 86 Sr ratio sequence analysis: Laser ablation coupled with multi-collector inductively coupled plasma mass spectrometry was used to perform line scanning analysis from the cusp along the dentin growth layer group to the pulp cavity to obtain the dentin 87 Sr / 86 Sr ratio series; dentin 87 Sr / 86 The raw data of the Sr ratio series were analyzed using a generalized additive model to obtain a smooth curve after fitting, which minimized the background noise while maintaining the important changes in the data; Step 5) Measurement of tooth growth layer groups: After laser ablation, the surface of the slice is photographed using a metallographic microscope, and the distance between each dentin growth layer group is measured along the laser ablation line to assist in interpretation 87 Sr / 86 The relationship between the Sr ratio series and the age of Yangtze finless porpoises; Step 6) Reconstruction of life history: Based on teeth 87 Sr / 86 The Sr ratio and its tooth growth age are determined by the water environment. 87 Sr / 86 The Sr ratio can be used to determine the habitat of the animal at that time.

2. The method for reconstructing the life history of Yangtze finless porpoises in the Yangtze River mainstream-Poyang Lake based on the Sr isotope ratio of dentin according to claim 1, characterized in that: In step 4), the RESOlution SE 193nm laser ablation system was used to perform micro-area in situ analysis of the dentin of the tooth, starting from the junction of the enamel and dentin along the dentin growth layer group to the pulp cavity; the aerosol after ablation entered the connected multi-receiver inductively coupled plasma mass spectrometer for analysis to obtain the dentin 87 Sr / 86 Sr ratio sequence; the analysis uses glass standard NIST SRM 610 to debug the instrument status, and the apatite standard Durango monitors the instrument during sample analysis 87 Sr / 86 The accuracy and repeatability of the Sr ratio; the laser line scanning speed is 5 μm / s, and the integration time of the laser ablation connected multi-collector inductively coupled plasma mass spectrometer is 0.5 s, that is, data within 0.25 μm on the laser beam spot forward path will be acquired every 0.5 seconds.

3. The method for reconstructing the life history of Yangtze River porpoises in the Yangtze River mainstream-Poyang Lake based on the Sr isotope ratio of dentin according to claim 1, characterized in that: In step 4), during the instrument raw data processing, the "onpeak zero" method is used to remove the interference of Kr and monitor 85 Rb signal is deducted 87 Rb 87 The interference of Sr, according to 88 Sr / 86 The isotopic abundance ratio of Sr in nature is 8.375209. The mass fractionation factor is calculated using the exponential law. 87 Sr / 86 The Sr ratio was used for instrument mass fractionation correction. Finally, the interference correction and mass fractionation correction were obtained. 87 Sr / 86 Sr measurements were performed using the mgcv package in the statistical software R. 87 Sr / 86 The Sr ratio data was smoothed and visualized using ggplot2.

4. The method for reconstructing the life history of Yangtze River porpoises in the Yangtze River mainstream-Poyang Lake based on the Sr isotope ratio of dentin according to claim 1, characterized in that: In step 5), after laser ablation, the slice surface was photographed using a metallographic microscope, and the distance between the light and dark bands of each adjacent dentin growth layer group was measured along the laser ablation line; 87 Sr / 86 The positions of the light and dark bands of each dentin growth layer group were marked on the smoothed data of Sr ratio to read the animal age. 87 Sr / 86 The Sr ratios correspond to the life stages of dentin formation, interpreting the habitat changes at different life stages.

5. The method for reconstructing the life history of Yangtze River porpoises in the Yangtze River mainstream-Poyang Lake based on the Sr isotope ratio of dentin according to claim 1, characterized in that: Step 6) through the dentin 87 Sr / 86 The fluctuation curve of Sr ratio and its tooth growth age are determined by water environment. 87 Sr / 86 The Sr ratio can be used to identify the habitats of Yangtze finless porpoises of different age groups, thereby reconstructing the life history of Yangtze finless porpoises; 87 Sr / 86 The Sr ratio range is 0.710-0.711; 87 Sr / 86 The Sr ratio range is 0.713-0.

716. Therefore, the main stream of the middle and lower reaches of the Yangtze River and the water body of Poyang Lake 87 Sr / 86 There are significant differences in Sr ratio. In summary, according to the 87 Sr / 86 The Sr ratio was used to determine the habitat background of the dead finless porpoises. 87 Sr / 86 The Sr ratio between 0.713 and 0.716 corresponds to the life history of Poyang Lake. 87 Sr / 86 The Sr ratio of 0.710-0.711 corresponds to the freshwater life history of the Yangtze River mainstream.

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