Large yellow croaker population identification method and apparatus based on stable carbon and oxygen isotopes in otoliths

Abstract

A large yellow croaker population identification method and apparatus based on stable carbon and oxygen isotopes in otoliths, which method and apparatus belong to the field of fish population identification. In the method, variance calculation and contribution analysis are performed to determine a first target isotope, thereby identifying whether a large yellow croaker is farmed or wild. The method is more objective and accurate. In the method, compared with conventional morphological or simple tagging methods, using variations in stable carbon and oxygen isotopes in otoliths caused by the impact of environments and dietary sources enables more accurate population discrimination, thereby effectively avoiding erroneous determination caused by factors such as small individual morphological variations or tag loss. Thus, in complex fishery market environments, farmed and wild large yellow croakers can be effectively distinguished, thereby helping to standardize the market order and protect wild fishery resources.

Description

Method and apparatus for identifying large yellow croaker populations based on stable carbon and oxygen isotopes in otoliths Technical Field

[0001] This application relates to the field of fish group identification technology, and in particular to a method and apparatus for identifying large yellow croaker groups based on stable carbon and oxygen isotopes of otoliths. Background Technology

[0002] In the fields of fisheries resource management and ecological research, accurately identifying the origin of large yellow croaker populations (such as farmed and wild) and more detailed population characteristics (such as the release nature of farmed populations and the nearshore or offshore nature of wild populations) is crucial for the scientific management of fisheries resources and a deeper understanding of marine ecosystems. As an important fisheries resource, the changes in the quantity and population structure of large yellow croaker have attracted widespread attention. Currently, the complexity of fisheries activities and the variability of the marine ecological environment make traditional population identification methods insufficient to meet the needs of precise research and management.

[0003] Currently, the identification of large yellow croaker populations mainly relies on morphological identification methods and molecular biological identification methods. Morphological identification methods distinguish different populations by observing and measuring the external morphological characteristics (such as body length, body height, scale characteristics, fin morphology, etc.) and internal anatomical structures (such as otolith morphology, number of vertebrae, etc.). Molecular biological identification methods use molecular marker technologies, such as DNA sequencing and microsatellite markers, to analyze differences in the gene sequences of large yellow croakers to identify populations.

[0004] However, morphological identification methods rely on the experience and subjective judgment of researchers, which is highly subjective and affects the accuracy and reliability of the results; molecular biological identification methods require professional laboratory equipment and technicians, and are costly and complex to operate. Summary of the Invention

[0005] In view of this, this application provides a method and apparatus for identifying large yellow croaker populations based on stable carbon and oxygen isotopes of otoliths, which can accurately and reliably understand the changes in the migration of large yellow croaker populations through simple operation.

[0006] Specifically, this application is implemented through the following technical solution:

[0007] The first aspect of this application provides a method for identifying large yellow croaker populations based on stable carbon and oxygen isotopes in otoliths, the method comprising:

[0008] The variances of carbon stable isotopes and oxygen stable isotopes in the large yellow croaker sample were calculated separately, and the contribution of the carbon stable isotopes and oxygen stable isotopes to the identification results was identified based on the variance results.

[0009] Based on the contribution, a first target isotope is determined, and the source type of the large yellow croaker population to be identified is determined according to the first target isotope. The source type includes farmed and wild.

[0010] For the first subpopulation whose source type is aquaculture, a second target isotope is determined based on the contribution and the first identification type of the first subpopulation. The first subpopulation is then clustered based on the second target isotope and the first time-related parameters to obtain a first identification result corresponding to the first identification type of the first subpopulation, where the first identification type is whether to release the fish.

[0011] For the second subpopulation whose source type is wild, a third target isotope is determined based on the contribution and the second identification type of the second subpopulation. The second subpopulation is then clustered based on the third target isotope and the second time-related parameters to obtain the second identification result corresponding to the second identification type of the second subpopulation. The second identification type is whether it is near the sea.

[0012] The identification results of the large yellow croaker population to be identified are obtained by combining the aquaculture type, the first identification result, and the second identification result.

[0013] The second aspect of this application provides a device for identifying large yellow croaker populations based on otolith carbon and oxygen stable isotopes, the device comprising an identification module, a processing module, and an acquisition module;

[0014] The identification module is used to calculate the variances of carbon stable isotopes and oxygen stable isotopes in the large yellow croaker sample, and to identify the contribution of the carbon stable isotopes and oxygen stable isotopes to the identification results based on the variance results.

[0015] The identification module is further configured to determine a first target isotope based on the contribution, and to identify the source type of the large yellow croaker population to be identified based on the first target isotope, wherein the source type includes farmed and wild.

[0016] The processing module is used to determine a second target isotope for the first sub-population whose source type is aquaculture, based on the contribution and the first identification type of the first sub-population, and to cluster the first sub-population based on the second target isotope and the first time-related parameters to obtain a first identification result corresponding to the first identification type of the first sub-population, wherein the first identification type is whether to release.

[0017] The processing module is further configured to determine a third target isotope for the second sub-population whose source type is wild, based on the contribution and the second identification type of the second sub-population, and to cluster the second sub-population based on the third target isotope and the second time correlation parameter to obtain a second identification result corresponding to the second identification type of the second sub-population, wherein the second identification type is whether it is near the sea.

[0018] The acquisition module is used to combine the aquaculture type, the first identification result, and the second identification result to obtain the identification result of the large yellow croaker population to be identified.

[0019] This application provides a method and apparatus for identifying large yellow croaker populations based on otolith carbon and oxygen stable isotopes. Considering that both carbon and oxygen stable isotopes are sensitive to different aspects of large yellow croaker and can contribute to the identification results, and taking into account the need to identify different types such as wild or farmed, near-shore or offshore, lifelong farmed or released, the method utilizes both isotopes simultaneously. Compared to traditional methods that fuse identification results, this invention determines their contribution to the identification results by calculating the variance of carbon and oxygen stable isotopes, and then uses the isotope with the highest contribution to obtain the large yellow croaker population identification result. This method effectively utilizes the information carried by stable isotopes in otoliths, maximizing the use of the sensitivity of different isotopes to the characteristics of large yellow croaker populations, overcoming the problems of traditional morphological identification methods being greatly affected by environmental factors, highly subjective, and unable to distinguish subtle differences. Between some morphologically similar farmed and wild large yellow croakers, stable isotope characteristics can provide a more objective and accurate basis for differentiation, helping fisheries resource management departments to accurately grasp the source of large yellow croakers in the market. For the first subpopulation of farmed large yellow croaker, further classification based on whether or not they were released into the wild was used. Clustering with the second target isotope and the first time-related parameter yielded the first identification result, clearly distinguishing between released and non-released farmed large yellow croaker. This is significant for evaluating the effectiveness of stock enhancement and release programs. For the second subpopulation of wild large yellow croaker, classification based on whether they were near-shore was used. Clustering with the third target isotope and the second time-related parameter yielded the second identification result. This helps to gain a deeper understanding of the ecological distribution of wild large yellow croaker, avoiding the use of complex model training and image recognition algorithms, reducing the complexity of large yellow croaker identification, while improving the accuracy of identification. This is of great value for studying the ecological habits, migration patterns, and the impact of different marine environments on the growth and development of wild large yellow croaker. Attached Figure Description

[0020] Figure 1 is a flowchart of an embodiment of the method for identifying large yellow croaker populations based on otolith carbon and oxygen stable isotopes provided in this application;

[0021] Figure 2 is a schematic diagram of the otoliths shown in this application;

[0022] Figure 3 is a schematic diagram of the variance analysis results exemplarily shown in this application;

[0023] Figure 4 is a schematic diagram of the clustering results of the first target isotope values ​​as exemplarily shown in this application;

[0024] Figure 5 is a schematic diagram of the clustering results of the first subgroup as exemplarily shown in this application;

[0025] Figure 6 is a schematic diagram of the second subgroup clustering results exemplarily shown in this application;

[0026] Figure 7 shows the variation of the mean values ​​of carbon-stabilized elements and oxygen-stabilized elements in otolith samples from different populations of large yellow croaker from the core to the second winter age, as shown in this application.

[0027] Figure 8 is a schematic diagram of a defined life path as exemplarily shown in this application;

[0028] Figure 9 is a schematic diagram of the structure of a first embodiment of the device for identifying large yellow croaker populations based on otolith carbon and oxygen stable isotopes provided in this application. Detailed Implementation

[0029] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application.

[0030] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used herein are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0031] It should be understood that although the terms first, second, third, etc., may be used in this application to describe various information, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."

[0032] The following specific embodiments are given to illustrate the technical solution of this application in detail.

[0033] Figure 1 is a flowchart of an embodiment of the method for identifying large yellow croaker populations based on stable carbon and oxygen isotopes of otoliths provided in this application. Referring to Figure 1, the method provided in this embodiment may include:

[0034] S101. Calculate the variances of carbon stable isotopes and oxygen stable isotopes in the large yellow croaker sample, and identify the contribution of the carbon stable isotopes and oxygen stable isotopes to the identification results based on the variance results.

[0035] It should be noted that this application studies the changes in the migration of large yellow croaker populations by measuring the content of carbon and oxygen stable isotopes in the otoliths of large yellow croaker. Specifically, the carbon stable isotope chosen is δ¹³C (carbon-13 isotope ratio, specifically the ratio of carbon-13 to carbon-12), and the oxygen stable isotope is δ¹⁸O (oxygen-18 isotope ratio, specifically the ratio of oxygen-18 to oxygen-16). This is because different food sources have different δ¹³C characteristics. In an ecosystem, plants absorb carbon dioxide and synthesize organic matter through photosynthesis. C3 plants (such as most temperate plants) and C4 plants (such as some tropical herbaceous plants) have different absorption and fractionation processes of carbon-12 and carbon-13 during photosynthesis, resulting in significant differences in their δ¹³C value ranges. Large yellow croaker feed on phytoplankton or other organisms, and the δ¹³C characteristics of their food sources are transferred and recorded in the otoliths. For example, in aquaculture environments, the feed composition of large yellow croaker is relatively fixed, and its δ13C value may differ from that of food sources in the natural environment. If the feed contains more C4 plant components, the δ13C value of otoliths in farmed large yellow croaker may be relatively low; while wild large yellow croaker feed on a variety of organisms in the natural environment, and the δ13C value of its otoliths is affected by the combined δ13C values ​​of different organisms in the food web, making δ13C an effective indicator for tracking the food source and ecological niche of large yellow croaker.

[0036] When the food source of large yellow croaker changes, such as migrating from one area to another or being released from an artificial breeding environment into the natural environment, the change in its diet composition will lead to a corresponding change in the δ13C value of its otoliths. For example, after being released, large yellow croakers gradually begin to feed on plankton, small fish and shrimp in their natural marine environment, which may cause the δ13C value to gradually increase and approach the isotopic characteristics of wild large yellow croakers. This change can be used to track the life history and environmental changes of large yellow croakers.

[0037] The δ¹⁸O value in seawater is closely related to water temperature and salinity. Lower water temperatures lead to a relative enrichment of 18O in the seawater, resulting in a higher δ¹⁸O value; increased salinity also raises the δ¹⁸O value. During their growth, the otoliths of large yellow croaker are in isotopic equilibrium with the surrounding seawater, and their δ¹⁸O values ​​record changes in temperature and salinity of their environment. For example, offshore environments typically have lower temperatures and higher salinity, so the otoliths of large yellow croaker living in the open sea may have higher δ¹⁸O values; while nearshore environments have relatively higher temperatures and lower salinity, so the δ¹⁸O values ​​of nearshore large yellow croaker otoliths may be lower. This close correlation with the environment allows δ¹⁸O to effectively reflect the characteristics of the large yellow croaker's living environment.

[0038] The migratory behavior of large yellow croaker also leaves traces on the δ18O values ​​of otoliths. When large yellow croaker migrates from one environment to another, such as from a low-salinity estuary to a high-salinity open sea, the δ18O values ​​of the otoliths will change accordingly. By analyzing the changes in δ18O values ​​of different parts of the otoliths (such as the core, wintering point, and edge), the migratory routes of large yellow croakers can be inferred, and it can be determined whether they migrate between environments with different temperatures and salinities, thereby understanding their life history and ecological habits.

[0039] Stable carbon and oxygen isotopes (δ¹³C and δ¹⁸O) are relatively stable once formed in the otoliths of large yellow croaker. Compared to other biomarkers, they are less susceptible to interference from short-term physiological changes or chemical processes within the organism. It should also be noted that otoliths are calcium carbonate minerals with a relatively stable structure, capable of preserving carbon and oxygen isotope information over long periods. For example, during the growth of large yellow croaker, even if other tissue components within its body may change due to factors such as metabolism and disease, the stable isotopic composition of the otoliths can still reflect the environmental and dietary information accumulated during its growth, providing a reliable record for long-term ecological research and population tracing.

[0040] Furthermore, the global distribution of carbon and oxygen isotopes follows certain patterns and varies across different ecosystems and geographical regions, making δ¹³C and δ¹⁸O traceable. For example, seawater δ¹⁸O values ​​in different ocean areas have specific ranges; by comparing the δ¹⁸O values ​​in the otoliths of large yellow croaker with characteristic values ​​from known ocean areas, their possible habitat can be inferred. Similarly, the range of δ¹³C values ​​from different food sources also helps trace the position and origin of large yellow croaker in the food web.

[0041] In specific implementation, the variances of carbon stable isotopes and oxygen stable isotopes in the large yellow croaker sample are calculated separately, and the contribution of the carbon stable isotopes and oxygen stable isotopes to the identification results is identified based on the variance results, including:

[0042] (1) Process the otoliths of each sample in the large yellow croaker sample to obtain samples for stable isotope analysis.

[0043] It should be noted that the processing involves extracting otoliths from the auditory sac of the head of a large yellow croaker sample, numbering the otoliths, cleaning them uniformly with ethanol, and drying them in an oven. After embedding and fixing the otoliths with epoxy resin, the samples are placed in an oven at 38°C overnight to solidify. After demolding, the otolith number is written directly above the otolith, and a thin slice containing the otolith core, approximately 2 mm thick, is cut along the cross-section using a cutting machine and attached to a glass slide. Under a microscope, the approximate outline is found, and the slice is polished sequentially using 500-grit, 2000-grit, and 4000-grit sandpaper, with the core and growth rings identified. This process is repeated until the core is almost exposed. A polishing machine equipped with a woven cloth polishing disc and polishing solution is then used to polish until the core is fully exposed and the surface is free of obvious scratches. The processed otolith slices are then ultrasonically cleaned in MQ (pure water system) water for 5 minutes, and then dried overnight at 38°C.

[0044] (2) The values ​​of carbon stable isotopes and oxygen stable isotopes at different positions in the otoliths of the sample were determined using a stable isotope analyzer.

[0045] It should be noted that a microsampler or a stable isotope mass spectrometer can be used for measurement. The sampling diameter can be 500 μm, and the sampling locations are the otolith core, the winter point, and the otolith edge. Figure 2 is a schematic diagram of the otolith shown in this application. Referring to Figure 2, the otolith core, the first winter point, the second winter point, and the otolith edge can be clearly observed.

[0046] (3) Based on the values, calculate the mean values ​​of carbon stable isotopes and oxygen stable isotopes at the same location for all samples.

[0047] It should be noted that the mean reflects the average level of carbon or oxygen stable isotopes at a given location across all samples. In population analyses, the mean may differ between different populations (e.g., farmed and wild large yellow croaker populations) at the same location. For example, the mean carbon stable isotope at the otolith core of a farmed large yellow croaker population might be significantly lower than that of a wild large yellow croaker population. For a detailed explanation of the mean, please refer to the relevant technical descriptions.

[0048] (4) Calculate the variance of carbon stable isotopes and oxygen stable isotopes in the large yellow croaker sample based on the mean, and identify the contribution of carbon stable isotopes and oxygen stable isotopes to the identification results based on the variance analysis results.

[0049] Specifically, the contribution of carbon stable isotopes and oxygen stable isotopes to the identification results is identified based on the variance analysis results, including: determining the differences in the proportions of carbon stable isotopes and oxygen stable isotopes under different first identification types and different second identification types according to the variance analysis results; and identifying the contribution of carbon stable isotopes and oxygen stable isotopes to the identification results based on the proportion differences and the environmental factors corresponding to the carbon stable isotopes and oxygen stable isotopes respectively. Figure 3 is a schematic diagram of the variance analysis results exemplarily shown in this application. Please refer to Figures a and b in Figure 3 to see that carbon stable isotopes contribute significantly to identifying whether the large yellow croaker population originates from farming or the wild.

[0050] Specifically, based on known sample types, wild large yellow croaker otoliths exhibit a wide range of stable carbon isotope (δ13C) values ​​with low mean differences and relatively large differences. However, farmed species show smaller differences in stable carbon isotope values. Therefore, if the population to be identified has a wide range of stable carbon isotope values ​​with large mean differences, it indicates that it is a wild species; otherwise, it is a farmed species.

[0051] Based on the preceding description, similarly, for samples of known types, when it's necessary to distinguish between nearshore and offshore origins, the variance of δ18O accounts for a significantly different proportion of the total variance. In this case, δ18O contributes greatly to identifying whether a large yellow croaker population originates from nearshore or offshore areas. Specifically, nearshore large yellow croaker otoliths exhibit a wide range of stable oxygen isotope (δ18O) values, with low mean differences but relatively large variations. However, offshore types show smaller differences in stable oxygen isotope values. Therefore, if the population to be identified exhibits a wide range of stable oxygen isotope values ​​and large mean differences, it indicates a nearshore type; conversely, it indicates a deep-sea type. This is because nearshore environments are relatively complex and variable, influenced by factors such as terrestrial runoff and shallow-sea ecosystems, leading to larger fluctuations in δ18O values ​​in large yellow croaker otoliths. However, offshore types show smaller differences in stable oxygen isotope values, as the offshore environment is relatively stable and homogeneous, resulting in more stable δ18O values ​​in the otoliths of large yellow croaker.

[0052] S102. Determine the first target isotope based on the contribution, and identify the source type of the large yellow croaker population to be identified based on the first target isotope. The source type includes farmed and wild.

[0053] It should be noted that determining the first target isotope based on the contribution, and identifying the origin type of the large yellow croaker population to be identified based on the first target isotope, includes:

[0054] (1) Based on the relative magnitude of the contribution, the first target isotope is determined to be a carbon stable isotope.

[0055] It should be noted that, according to the analysis of variance results, the different proportions of carbon stable isotopes and oxygen stable isotopes in the contribution affect the differentiation of the origin of the current large yellow croaker population. Specifically, carbon stable isotopes mainly affect the differentiation between farmed and wild populations, while oxygen stable isotopes mainly affect the differentiation between nearshore and offshore populations. In other words, carbon stable isotopes contribute significantly to the identification of farmed or wild populations, while oxygen stable isotopes contribute significantly to the identification of nearshore or offshore populations. When the primary target isotope is carbon stable isotopes, it indicates that the main distinction is made between farmed and wild origins of the large yellow croaker population.

[0056] (2) Cluster the values ​​of the first target isotope in the first region.

[0057] It should be noted that the first region is the otolith core region, which is formed during the early growth stage of the large yellow croaker and is the central part where otoliths initially form. Information such as the environment and food sources during this period is recorded in the isotopic composition of the otolith core. For fish, the early living environment has a profound impact on their subsequent growth, development, and physiological characteristics. For example, in the juvenile stage, the food sources of large yellow croaker are relatively singular, mainly determined by their specific environment (such as plankton near the hatchery). The first target isotopic value of the otolith core region can reflect the characteristics of this early food source. By clustering these values, large yellow croaker samples with similar early food sources and growth environments can be grouped into one category.

[0058] (3) Based on the mean difference of the first target isotope in the clustering results, the source type of the large yellow croaker population to be identified is determined.

[0059] When distinguishing between farmed and wild large yellow croaker, the isotopic characteristics of the otolith core region are a crucial starting point. Farmed and wild large yellow croaker often exist in different environments during their early growth stages. Farmed large yellow croaker typically grow in artificially controlled environments, with relatively stable early food supplies (such as specially formulated feed) and water quality conditions. This results in the first target isotope value of their otolith core region exhibiting different characteristics compared to wild large yellow croaker. Figure 4 is a schematic diagram of the clustering results of the first target isotope values, exemplarily shown in this application. Referring to Figure 4, the first target isotopes in the red category are significantly different from those in the blue category, allowing for the differentiation between farmed and wild species based on the clustering results.

[0060] S103. For the first sub-population whose source type is aquaculture, determine the second target isotope based on the contribution and the first identification type of the first sub-population, and cluster the first sub-population based on the second target isotope and the first time-related parameters to obtain the first identification result corresponding to the first identification type of the first sub-population, wherein the first identification type is whether to release.

[0061] It should be noted that determining the second target isotope based on the contribution and the first identification type of the first subgroup includes: identifying the first identification type; and determining the second target isotope based on the difference in the contribution ratio of the carbon stable isotope and the oxygen stable isotope in the identified first identification type.

[0062] The contributions of carbon and oxygen stable isotopes to the identification results were determined using the preceding analysis of variance. This contribution reflects the relative importance of the two isotopes in distinguishing different population characteristics. After identifying the first identification type (i.e., whether to release), the second target isotope needs to be determined based on the difference in the contribution ratios of carbon and oxygen stable isotopes during this process. If, in determining whether to release, changes in carbon stable isotopes (e.g., the shift from typical carbon isotope values ​​in aquaculture environments to those in wild environments) play a crucial role in the release determination, meaning that carbon stable isotopes contribute significantly to the release identification result, then carbon stable isotopes can be identified as the second target isotope. This is because after release, the food source of large yellow croaker may change, causing the carbon stable isotopes in the otoliths to better reflect this transition from aquaculture to the natural environment.

[0063] Furthermore, after determining the second target isotope, the first subgroup is clustered based on the second target isotope and the first time-related parameters to obtain the first identification result corresponding to the first identification type of the first subgroup. This includes: obtaining the first time-related parameters and the second target isotope of each individual in the first subgroup; selecting a clustering method based on the characteristics of the first time-related parameters and the second target isotope to perform clustering; analyzing the differences in the clustering results based on the clustering results and known fishing information, and obtaining the first identification result based on the differences.

[0064] It should be noted that the first-time-related parameters here refer to the slope from the otolith core to the first winter age and the first winter age value. These parameters reflect the changes in large yellow croaker during specific growth stages. For example, the slope from the otolith core to the first winter age reflects the rate of change in the isotopic characteristics of the otoliths during the period from early juvenile stage to the first winter age. This rate of change may be closely related to factors such as changes in the growth environment (e.g., release from a culture environment to a natural environment) and changes in food sources. The first winter age value is an isotopic measurement at a key time point, which also contains important growth information.

[0065] Based on the second target isotope determined in the previous steps, the value of that isotope for each individual in the first subpopulation is obtained. These values ​​are measured for each large yellow croaker individual and represent their isotopic characteristics at a specific location. Since both first-time correlation parameters and second-target isotope data are available, the data possesses a certain degree of complexity and multidimensionality, requiring consideration of factors such as data distribution, data volume, and the presence of obvious grouping trends. Based on these characteristics, the most suitable clustering method is selected for clustering. After clustering, the results are observed. The characteristics of the second target isotope values ​​and first-time correlation parameters of individuals within each cluster are analyzed. For example, individuals in a certain cluster may have similar second target isotope values ​​and similar slopes and first-winter age values ​​from the otolith core, indicating that these individuals exhibit similar change patterns during growth.

[0066] The clustering results are compared and analyzed with known fishing information. Fishing information may include fishing location, fishing time, and whether the fish were caught near the release area. If most individuals in a cluster were caught near the release area, and their second target isotope values ​​and first-time related parameters show the expected change pattern after release (e.g., the second target isotope value approaches the characteristics of wild large yellow croaker, and the slope of the otolith core changes significantly from the first winter age), then it can be inferred that the individuals in this cluster are released. By comprehensively analyzing the differences between the clustering results and the fishing information, the first identification result for each individual in the first subgroup is determined, i.e., whether they are released large yellow croaker. For example, if the clustering results highly match the fishing information and can clearly distinguish between released and non-released individuals, an accurate first identification result can be obtained. Figure 5 is a schematic diagram of the clustering results of the first subgroup as exemplarily shown in this application. Referring to Figure 5, by comparing the red and blue categories and our known fishing information, it can be considered that the red category with a higher slope is the stock enhancement and release group, and the blue category with a lower slope is the lifelong aquaculture group.

[0067] S104. For the second subgroup whose source type is wild, determine the third target isotope based on the contribution and the second identification type of the second subgroup. Cluster the second subgroup based on the third target isotope and the second time correlation parameter to obtain the second identification result corresponding to the second identification type of the second subgroup. The second identification type is whether it is near the sea.

[0068] It should be noted that the method for determining the third target isotope is described above in the section on determining the second target isotope. The third target isotope is different from the second target isotope; specifically, the third target isotope is an oxygen stable isotope, meaning that oxygen stable isotopes contribute significantly to the identification results for near-shore or offshore areas.

[0069] Specifically, the second subgroup is clustered according to the third target isotope and the second time correlation parameter to obtain the second identification result corresponding to the second identification type of the second subgroup, including: obtaining the second time correlation parameter and the third target isotope of each individual in the second subgroup; selecting a clustering method based on the characteristics of the second time correlation parameter and the third target isotope to perform clustering; and obtaining the second identification result based on the variation relationship between the second time correlation parameter and the variance difference of the third target isotope in the clustering result.

[0070] It should be noted that the second time-related parameters include the slope from the otolith core to the first wintering age and the slope from the first wintering age to the second wintering age. These parameters can reflect the changes in wild large yellow croaker at different growth stages. For example, the slope from the otolith core to the first wintering age reflects the growth trend from the early juvenile stage to the first wintering age, while the slope from the first wintering age to the second wintering age reflects the changes in subsequent growth stages. These slopes may differ in wild large yellow croakers in different nearshore or offshore environments because environmental factors (such as water temperature, food resources, etc.) can affect their growth rate and the fractionation process of isotopes in the otoliths.

[0071] The purpose of obtaining the third target isotope value of each individual in the second subgroup is to distinguish wild large yellow croaker populations under different environments. The third target isotope value of each individual reflects the isotopic characteristics of wild large yellow croaker individuals at specific locations of otoliths. These characteristics are affected by factors such as food source and environmental conditions.

[0072] Simultaneously considering the properties of the second time-related parameters and the third target isotope data, and selecting an appropriate clustering method based on the characteristics of the data, natural clusters in the data can be better discovered, without being limited by the preset number of clusters and data shape. After completing the clustering, the changing relationships between the second time-related parameters of individuals within each cluster are observed. For example, in a cluster, if the slope from the otolith core to the first winter age and the slope from the first winter age to the second winter age of most individuals show a stable proportional relationship, this may indicate that these individuals grew under similar environmental conditions and have similar growth patterns. The changing relationships of these slopes may differ between different clusters, which helps to distinguish wild large yellow croaker populations in different environments. Figure 6 is a schematic diagram of the second sub-population clustering results exemplarily shown in this application. Referring to Figure 6, by comparing the red and blue categories, and our known fishing information, the red category can be considered as nearshore wild populations, and the blue category as offshore wild populations. At the same time, the variance of the third target isotope within each cluster is analyzed. Variance can reflect the degree of dispersion of the data. If the variance of the third target isotope within a cluster is small, it indicates that individuals within that cluster are relatively similar in this isotopic characteristic, potentially suggesting they originate from relatively stable and similar environments. Differences in the variance of the third target isotope between different clusters can serve as a basis for distinguishing different wild large yellow croaker populations. For example, nearshore wild large yellow croakers may have a relatively small variance in their third target isotope due to relatively less environmental variation; while offshore wild large yellow croakers may have a relatively large variance due to more complex environmental factors.

[0073] By comprehensively considering the changes in the second time-related parameters in the clustering results and the variance differences of the third target isotope, the second identification result of each individual in the second subgroup is determined. That is, to determine whether the wild large yellow croaker belongs to a nearshore group or an offshore group. For example, in one possible implementation, the changes in the slope (s1) from the otolith core to the first winter age and the slope value (s2) from the first winter age are considered. If there is a change in slope from negative to positive (s1*s2<0) and Δk=s1-s2>1, it is judged as an offshore group. If there is no change in slope (s1*s2>0) or a change in slope from negative to positive (s1*s2<0 and Δk=s1-s2<0.5), it is judged as a nearshore group.

[0074] S105. Combine the aquaculture type, the first identification result, and the second identification result to obtain the identification result of the large yellow croaker population to be identified.

[0075] Specifically, by combining the aquaculture type, the first identification result, and the second identification result, the identification results of the large yellow croaker population to be identified can be obtained, including populations released for stock enhancement, populations cultured for life, nearshore wild populations, and offshore wild populations. Furthermore, based on the identification results, the sample average values ​​of oxygen-stabilized elements and carbon-stabilized elements in otolith samples from different large yellow croaker populations from the core to the second winter age can be obtained. Figure 7 shows the variation of the sample average values ​​of carbon-stabilized elements and oxygen-stabilized elements in otolith samples from different large yellow croaker populations from the core to the second winter age, as shown in this application. Referring to Figure 7, Figure a shows the variation of the sample average values ​​of carbon-stabilized elements in otolith samples from different large yellow croaker populations from the core to the second winter age, and Figure b shows the variation of the sample average values ​​of oxygen-stabilized elements in otolith samples from different large yellow croaker populations from the core to the second winter age. Based on Figure 7, the mean changes of carbon and oxygen-stabilized elements in different populations can be better understood, thereby enabling population differentiation and ecological characteristic responses.

[0076] It should also be noted that, after combining the aforementioned aquaculture type, the first identification result, and the second identification result to obtain the identification result of the large yellow croaker population to be identified, the following steps are taken:

[0077] (1) Determine the nearshore population and offshore population based on the identification results.

[0078] Based on the previous comprehensive identification results of the large yellow croaker population, the wild large yellow croaker population is further subdivided into nearshore populations and offshore populations. Specifically, this division is based on the judgment of the second identification results.

[0079] (2) Analyze the variation trend of stable isotopes of nearshore and offshore populations to identify spawning grounds.

[0080] It should be noted that for both nearshore and offshore populations, the trends in carbon and oxygen stable isotopes at different growth stages (e.g., from juvenile to sexual maturity) were studied separately. During the breeding season, the physiological state and behavior of large yellow croakers change, and their food intake patterns and living environment may undergo specific changes, which are reflected in the stable isotope composition of otoliths. For example, female large yellow croakers may gather in specific food-rich areas before spawning, leading to changes in food sources and thus altering the carbon stable isotope values ​​in otoliths; at the same time, environmental factors such as water temperature and salinity in the breeding grounds may also affect the fractionation process of oxygen stable isotopes in otoliths.

[0081] By analyzing stable isotope data from a large number of samples, common patterns of change appearing before and after the breeding season can be identified. For example, it might be found that as nearshore populations approach the breeding season, carbon stable isotope values ​​gradually approach a specific range, while oxygen stable isotope values ​​also show corresponding patterns of change. These trends can serve as clues for identifying spawning grounds. If large yellow croaker samples caught in a certain sea area generally show this specific pattern of stable isotope changes, and the ecological environment of that sea area (such as seabed topography and currents) is also suitable for large yellow croaker spawning, then it can be inferred that this sea area may be a spawning ground.

[0082] (3) The spawning grounds are corrected by combining the environmental data of the living areas of the nearshore and offshore groups, and the overwintering grounds corresponding to the spawning grounds are determined.

[0083] It should be noted that detailed environmental data on the habitats of nearshore and offshore populations, including seasonal variations in water temperature, salinity distribution, current velocity and direction, seabed topography, and the structure of marine ecosystems (such as plankton distribution and seabed sediment characteristics), are used to verify and correct spawning grounds initially identified based on stable isotope variation trends. For example, if the water temperature near the spawning grounds inferred from stable isotopes does not match the suitable temperature range for large yellow croaker reproduction during the breeding season, or if the area lacks the necessary ecological conditions, the assessment of the spawning grounds needs to be adjusted.

[0084] After identifying relatively accurate spawning grounds, overwintering grounds are determined by combining environmental data and the life history characteristics of the large yellow croaker. The environmental conditions of overwintering grounds are usually related to the spawning grounds, but are also influenced by the physiological needs of the large yellow croaker itself. For example, overwintering grounds generally require relatively stable water temperatures (within the low temperature range that the large yellow croaker can tolerate), sufficient food resources (to maintain the basic energy needs of the large yellow croaker in winter), and suitable habitats (such as suitable water depth and relatively gentle water flow).

[0085] (4) Determine the farmed type and wild type based on the identification results.

[0086] The identification results will clarify whether the large yellow croaker belongs to the farmed or wild type, which is of great significance for subsequent research and management.

[0087] (5) Determine the life path based on the carbon and oxygen stable isotope variation trends of the farmed and wild types.

[0088] For farmed large yellow croaker, if release is implemented, analyzing the trends in carbon and oxygen stable isotope changes before and after release can reveal its activity path in the natural environment. After release, the food source of large yellow croaker may gradually shift from artificial feed to natural food, and the carbon stable isotope values ​​in its otoliths will change accordingly. Simultaneously, environmental changes (such as natural fluctuations in water temperature and salinity) will also affect the composition of oxygen stable isotopes in the otoliths. By tracking these changes, the activity range, migration routes, and relationships with wild populations of released farmed large yellow croaker in natural waters can be determined.

[0089] For wild-type large yellow croaker, its complete life path can be reconstructed based on the changes in its carbon and oxygen stable isotopes at different growth stages and in different regions. From the juvenile stage, the stable isotope information recorded in the otoliths can reflect its early living environment (such as the environmental characteristics of nearshore spawning areas). As it grows and develops, the large yellow croaker may migrate, and the isotope changes in its otoliths can track its migration routes, including foraging migration from nearshore to offshore, migration to spawning grounds during the breeding season, and migration to overwintering grounds during winter. Figure 8 is a schematic diagram of the determined life path exemplarily shown in this application. Referring to Figure 8, the specific regional ranges of the spawning grounds and the first and second wintering grounds of the large yellow croaker in the East China Sea can be clearly inferred. In Figure 8, label 1 represents the offshore spawning ground, label 2 represents the offshore overwintering ground in the second year, label 3 represents the nearshore spawning ground, label 4 represents the near-offshore overwintering ground in the first year, and label 5 represents the nearshore overwintering ground in the second year.

[0090] By further segmenting large yellow croaker populations (e.g., nearshore and offshore populations) and studying their ecological behavior in different marine environments, including locational identification of key life stages such as reproduction (spawning ground identification) and overwintering (overwintering ground determination), we can gain a deeper understanding of the large yellow croaker's role and behavioral patterns in the marine ecosystem. Clarifying the life paths of farmed and wild-caught large yellow croaker species helps to accurately grasp the distribution and dynamic changes of fishery resources, providing detailed data support for the formulation of reasonable fishery quotas, aquaculture planning, and resource conservation.

[0091] The method provided in this embodiment determines the first target isotope through variance calculation and contribution analysis, thereby identifying whether large yellow croaker is farmed or wild. This method is more objective and accurate. Compared with traditional morphological or simple labeling methods, utilizing the differences in stable carbon and oxygen isotopes in otoliths due to environmental and food source influences can more accurately classify populations, avoiding misjudgments caused by small individual morphological differences or lost markers. In the complex fisheries market environment, it can effectively distinguish between farmed and wild large yellow croaker, helping to regulate market order and protect wild fishery resources. Further subdivision of farmed and wild populations is possible, such as determining whether farmed populations should be released and whether wild populations are nearshore. This multi-level classification provides more detailed population information, which is of great significance for studying the ecological diversity, life history, and role in the ecosystem of large yellow croaker. It can help understand the survival and integration of released farmed large yellow croaker in the natural environment and assists in assessing the impact of stock enhancement and release measures on the ecosystem. Cluster analysis using time-related parameters and target isotopes can yield information on large yellow croaker at different growth stages. This helps reconstruct the life history of large yellow croaker, including changes in food sources and environmental shifts (such as from nearshore to offshore), thus providing a deeper understanding of its ecological adaptability and growth patterns. Furthermore, accurately identifying various types of large yellow croaker populations (farmed / wild, released / not released, nearshore / offshore) allows for the development of more reasonable catch quotas and regional restrictions based on the distribution, quantity, and growth status of different populations, thereby optimizing fisheries resource management.

[0092] Corresponding to the aforementioned embodiment of a method for identifying large yellow croaker populations based on stable carbon and oxygen isotopes of otoliths, this application also provides an embodiment of a device for identifying large yellow croaker populations based on stable carbon and oxygen isotopes of otoliths.

[0093] Figure 9 is a schematic diagram of the structure of a first embodiment of the device for identifying large yellow croaker populations based on otolith carbon and oxygen stable isotopes provided in this application. Referring to Figure 9, the device provided in this embodiment includes an identification module 910, a processing module 920, and an acquisition module 930;

[0094] The identification module 910 is used to calculate the variances of carbon stable isotopes and oxygen stable isotopes in the large yellow croaker sample, and to identify the contribution of the carbon stable isotopes and oxygen stable isotopes to the identification results based on the variance results.

[0095] The identification module 910 is further configured to determine a first target isotope based on the contribution, and to identify the source type of the large yellow croaker population to be identified based on the first target isotope, wherein the source type includes farmed and wild.

[0096] The processing module 920 is used to determine a second target isotope for the first sub-population whose source type is aquaculture, based on the contribution and the first identification type of the first sub-population, and to cluster the first sub-population based on the second target isotope and the first time-related parameters to obtain a first identification result corresponding to the first identification type of the first sub-population, wherein the first identification type is whether to release.

[0097] The processing module 920 is further configured to determine a third target isotope for the second sub-population whose source type is wild, based on the contribution and the second identification type of the second sub-population, and to cluster the second sub-population based on the third target isotope and the second time correlation parameter to obtain a second identification result corresponding to the second identification type of the second sub-population, wherein the second identification type is whether it is near the sea.

[0098] The acquisition module 930 is used to obtain the identification result of the large yellow croaker population to be identified by combining the aquaculture type, the first identification result, and the second identification result.

[0099] The apparatus in this embodiment can be used to execute the steps of the method embodiment shown in FIG1. ​​The specific implementation principle and process are similar and will not be described again here.

[0100] The specific implementation process of the functions and roles of each unit in the above device can be found in the implementation process of the corresponding steps in the above method, and will not be repeated here.

[0101] For the device embodiments, since they basically correspond to the method embodiments, the relevant parts can be referred to in the description of the method embodiments. The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this application according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0102] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for identifying large yellow croaker populations based on stable carbon and oxygen isotopes in otoliths, characterized in that, The method includes: The variances of carbon stable isotopes and oxygen stable isotopes in the large yellow croaker sample were calculated separately, and the contribution of the carbon stable isotopes and oxygen stable isotopes to the identification results was identified based on the variance results. Based on the contribution, a first target isotope is determined, and the source type of the large yellow croaker population to be identified is determined according to the first target isotope. The source type includes farmed and wild. For the first subpopulation whose source type is aquaculture, a second target isotope is determined based on the contribution and the first identification type of the first subpopulation. The first subpopulation is then clustered based on the second target isotope and the first time-related parameters to obtain a first identification result corresponding to the first identification type of the first subpopulation, where the first identification type is whether to release the fish. For the second subpopulation whose source type is wild, a third target isotope is determined based on the contribution and the second identification type of the second subpopulation. The second subpopulation is then clustered based on the third target isotope and the second time-related parameters to obtain the second identification result corresponding to the second identification type of the second subpopulation. The second identification type is whether it is near the sea. The identification results of the large yellow croaker population to be identified are obtained by combining the aquaculture type, the first identification result, and the second identification result.

2. The method according to claim 1, characterized in that, The calculation of the variances of carbon and oxygen stable isotopes in the large yellow croaker sample, and the identification of the contribution of the carbon and oxygen stable isotopes to the identification results based on the variance results, includes: The otoliths of each sample in the large yellow croaker sample were processed to obtain samples for stable isotope analysis. The values ​​of carbon and oxygen stable isotopes at different positions in the otoliths of the sample were determined using a stable isotope analyzer. Based on the aforementioned values, the mean values ​​of carbon stable isotopes and oxygen stable isotopes at the same location for all samples are calculated. The variances of carbon stable isotopes and oxygen stable isotopes in the large yellow croaker sample were calculated based on the mean, and the contribution of the carbon stable isotopes and oxygen stable isotopes to the identification results was identified based on the variance analysis results.

3. The method according to claim 2, characterized in that, The identification of the contribution of the carbon stable isotope and oxygen stable isotope to the identification result based on the variance analysis results includes: The differences in the proportions of carbon stable isotopes and oxygen stable isotopes under different first identification types and different second identification types were determined based on the results of the analysis of variance. Based on the aforementioned proportion differences and the environmental factors corresponding to the carbon stable isotopes and oxygen stable isotopes, the contribution of the carbon stable isotopes and oxygen stable isotopes to the identification results is identified.

4. The method according to claim 1, characterized in that, The step of determining the first target isotope based on the contribution and identifying the origin type of the large yellow croaker population to be identified based on the first target isotope includes: Based on the relative magnitude of the contribution, the first target isotope is determined to be a carbon stable isotope; Clustering is performed on the values ​​of the first target isotope in the first region; Based on the mean difference of the first target isotope in the clustering results, the origin type of the large yellow croaker population to be identified was determined.

5. The method according to claim 1, characterized in that, The step of determining the second target isotope based on the contribution and the first identification type of the first subgroup includes: Identify the first identification type; The second target isotope is determined based on the difference in the contribution ratio of carbon stable isotopes and oxygen stable isotopes in the first identification type.

6. The method according to claim 1, characterized in that, The first time-related parameter is the slope from the otolith core to the first winter age and the value of the first winter age; the second time-related parameter is the slope from the otolith core to the first winter age and the slope from the first winter age to the second winter age.

7. The method according to claim 1, characterized in that, The step of clustering the first subgroup based on the second target isotope and the first time correlation parameters to obtain the first identification result corresponding to the first identification type of the first subgroup includes: Obtain the first time-related parameters and the second target isotope of each individual in the first subgroup; Clustering is performed based on the first time-related parameters and the characteristics of the second target isotope using a clustering method. Based on the clustering results and known fishing information, the differences in the clustering results are analyzed, and the first identification result is obtained based on the differences.

8. The method according to claim 1, characterized in that, The step of clustering the second subgroup based on the third target isotope and the second time correlation parameter to obtain the second identification result corresponding to the second identification type of the second subgroup includes: Obtain the second time-related parameters and the third target isotope for each individual in the second subgroup; Clustering is performed based on the characteristics of the second time-related parameters and the third target isotope; The second identification result is obtained based on the variation relationship between the second time-related parameters in the clustering results and the variance difference of the third target isotope.

9. The method according to claim 1, characterized in that, After combining the aforementioned aquaculture type, the first identification result, and the second identification result to obtain the identification result of the large yellow croaker population to be identified, the process includes: Based on the identification results, nearshore and offshore populations were determined; Analyze the variation trends of stable isotopes in nearshore and offshore populations to identify spawning grounds; The spawning grounds are corrected by combining environmental data of the habitats of the nearshore and offshore groups, and the overwintering grounds corresponding to the spawning grounds are determined. The farmed and wild types are determined based on the identification results; Life paths were determined based on the carbon and oxygen stable isotope variation trends of the farmed and wild types.

10. A device for identifying large yellow croaker populations based on stable carbon and oxygen isotopes in otoliths, characterized in that, The device includes an identification module, a processing module, and an acquisition module; The identification module is used to calculate the variances of carbon stable isotopes and oxygen stable isotopes in the large yellow croaker sample, and to identify the contribution of the carbon stable isotopes and oxygen stable isotopes to the identification results based on the variance results. The identification module is further configured to determine a first target isotope based on the contribution, and to identify the source type of the large yellow croaker population to be identified based on the first target isotope, wherein the source type includes farmed and wild. The processing module is used to determine a second target isotope for the first sub-population whose source type is aquaculture, based on the contribution and the first identification type of the first sub-population, and to cluster the first sub-population based on the second target isotope and the first time-related parameters to obtain a first identification result corresponding to the first identification type of the first sub-population, wherein the first identification type is whether to release. The processing module is further configured to determine a third target isotope for the second sub-population whose source type is wild, based on the contribution and the second identification type of the second sub-population, and to cluster the second sub-population based on the third target isotope and the second time correlation parameter to obtain a second identification result corresponding to the second identification type of the second sub-population, wherein the second identification type is whether it is near the sea. The acquisition module is used to combine the aquaculture type, the first identification result, and the second identification result to obtain the identification result of the large yellow croaker population to be identified.

Images