A method for evaluating the suitability of spawning ground for Gymnocypris przewalskii

Abstract

The application discloses a kind of Qinghai Lake naked carp spawning ground suitability evaluation method, comprising the following steps: step 1: Qinghai Lake naked carp spawning ground investigation is carried out, and population distribution and habitat water environmental factor are obtained;Step 2: the preferred interval and weight of each environmental factor are analyzed, and the priority level of spawning ground is determined;Step 3: the behavior response of Qinghai Lake naked carp is observed through microhabitat simulation experiment, and the group Qinghai Lake naked carp substrate selection preference is obtained;Step 4: water power model of evaluation area is constructed;Step 5: Qinghai Lake naked carp habitat evaluation model is constructed, and the suitability of Qinghai Lake naked carp habitat is evaluated in combination with water power model;The application can be applied to Qinghai Lake naked carp in situ habitat restoration to provide theoretical basis support and engineering application measure suggestion, fully play its protection role to Qinghai Lake naked carp, help to protect Qinghai Lake ecological environment and Qinghai Lake naked carp population.

Description

Technical Field

[0001] This invention relates to the field of ecology and Qinghai Lake naked carp conservation technology, and in particular to a method for evaluating the suitability of Qinghai Lake naked carp spawning grounds. Background Technology

[0002] Qinghai Lake is the largest inland saltwater lake in my country, located on the Qinghai-Tibet Plateau. It is an internationally important protected wetland and a national nature reserve. The Qinghai Lake naked carp (… Gymnocyprisprzewalskii Locally known as "Huangyu," it belongs to the order Cypriniformes, family Cyprinidae, subfamily Schizothorax. Schizo-thoracinae ), Qinghai Lake naked carp ( Gymnocypris The Qinghai Lake naked carp (Gymnocypris qinghaihuensis), the only economically important species in Qinghai Lake, possesses biological characteristics such as a long lifespan, slow growth, and late sexual maturity, occupying an irreplaceable core position in the Qinghai Lake ecosystem. From the early 1960s to the late 1990s, human activities (damming, irrigation, overfishing, etc.) threatened the survival of the Qinghai Lake naked carp, reducing its population from 690 million to less than 25 million. In 2004, the Qinghai Lake naked carp was listed in the "China Species Red List" as a national second-class endangered protected animal. To restore the Qinghai Lake naked carp population, efforts such as restocking and habitat restoration have gradually gained importance. Currently, restocking involves using artificial breeding techniques to hatch fish eggs and cultivate fry before releasing them into Qinghai Lake. This can increase the Qinghai Lake naked carp population in the short term, but artificial breeding conditions differ from those in natural water bodies, and the adaptability of released Qinghai Lake naked carp to the wild environment remains questionable. The key to a safe and sustainable resource recovery process for the Qinghai Lake naked carp lies in how to restore its natural habitat to create habitat conditions that meet its needs.

[0003] Therefore, understanding the spawning grounds and habitat conditions of the Qinghai Lake naked carp is urgent, and it is necessary to conduct research on the behavioral responses of the Qinghai Lake naked carp to habitat parameters. This requires a comprehensive understanding of the natural reproductive ecological needs of the Qinghai Lake naked carp. However, current research on the habitat suitability assessment of the Qinghai Lake naked carp during the spawning period in the Shaliu River section is relatively limited. Systematic and in-depth studies on the distribution of the Qinghai Lake naked carp population and habitat suitability in this region, considering the characteristics of its aquatic ecological environment, are lacking. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned shortcomings and provide a method for evaluating the suitability of spawning grounds for naked carp in Qinghai Lake. This method can be applied to the suitability evaluation of spawning grounds for naked carp in Qinghai Lake, providing data support and implementation direction for habitat restoration of naked carp in Qinghai Lake.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A method for evaluating the suitability of spawning grounds for naked carp in Qinghai Lake includes the following steps: Step 1: Conduct a survey of the spawning grounds of naked carp in Qinghai Lake to obtain information on population distribution and habitat aquatic environmental factors; Step 2: Analyze the preference range and weight of each environmental factor to determine the priority level of spawning grounds; Step 3: Observe the behavioral response of Qinghai Lake naked carp through microhabitat simulation experiments to obtain the substrate selection preferences of the Qinghai Lake naked carp population; Step 4: Construct a hydrodynamic model of the evaluation area; Step 5: Construct an evaluation model for the habitat of the naked carp in Qinghai Lake, and evaluate the suitability of the habitat of the naked carp in Qinghai Lake in combination with a hydrodynamic model.

[0006] Preferably, in step 1, the method for investigating the spawning grounds of the Qinghai Lake naked carp is as follows: based on the migration and breeding season of the Qinghai Lake naked carp, a habitat survey is carried out in the study area, survey points are selected, and the bottom sediment, flow velocity, water depth, and sex of the survey points are investigated.

[0007] Preferably, in step 2, the weight values ​​of each environmental factor are calculated using the entropy weight method.

[0008] Preferably, the weight values ​​of each environmental factor are calculated using the entropy weight method. The calculation steps are as follows: (1) Data matrix standardization, the standardization formula is:

[0009] In the formula For standardized indicator values, As the initial standard value, This is the maximum value of the indicator. This is the minimum value of this indicator; Standardized indicator values; (2) Calculation of index entropy value: The entropy of the i-th index is defined as:

[0010]

[0011] In the formula, k= , k is the Boltzmann constant, and n is the number of objects being evaluated; Let be the entropy value of the i-th index; The entropy value of the indicator; (3) Calculation of indicator weights: Based on the indicator entropy value, the formula for calculating the weights of each indicator is as follows:

[0012] The entropy weight method is used to determine the index weights. ; (4) Calculation of indicator weight vector, the calculation formula is:

[0013] Preferably, in step 2, based on the obtained weight values ​​of environmental factors, the priority level of spawning grounds is analyzed using the TOPSIS integrated model.

[0014] Preferably, the specific process of analyzing the priority hierarchy of spawning grounds using the TOPSIS integrated model is as follows: Weighted decision matrix Sure:

[0015] In the formula For the indicator weight vector, Standardized indicator values; Positive and negative ideal values Sure: ;

[0016]

[0017] Positive and negative ideal distance calculate:

[0018]

[0019] Each object to be evaluated Evaluation reference value calculation:

[0020] Based on the calculation result F, the priority levels of each spawning ground are defined as follows: 0.3≤F<1 is the preferred type of suitable habitat, 0.2≤F<0.3 is the main type of suitable habitat, 0.1≤F<0.2 is the secondary type of suitable habitat, and F<0.1 is the alternative type of suitable habitat.

[0021] Preferably, step 3 specifically involves: providing a circular tank internally equipped with detachable filter and drainage components as a habitat substrate simulation pond; dividing the bottom of the simulation pond into zones and arranging five typical habitat substrates, specifically including: mud and sand with a diameter not exceeding 0.01 cm, gravel with a diameter of 0.1 to 0.2 cm, small to medium-sized pebbles with a diameter of 2 to 5 cm, large pebbles and stones with a diameter of 10 to 25 cm and smooth surfaces, and large pebbles and stones with a diameter of 10 to 25 cm and a natural bottom mud layer on their surface; transferring the fish to be tested into the simulation pond containing the above five substrates to conduct a substrate preference test. During the experimental phase, the behavior of the fish school was continuously recorded using an underwater camera. Subsequently, the video activity was processed using automatic frame-segmentation and tracking technology. Specifically, the continuous video stream was parsed into a sequence of single-frame images at a set frame rate. The spatial coordinates of the experimental fish in each frame were extracted using an image recognition algorithm. These spatial coordinates were then compared with the boundaries of five pre-defined substrate regions to determine the substrate type in each frame. Finally, by accumulating the total number of frames in which the experimental fish appeared in each substrate region and combining it with the set frame rate, the actual dwell time of the experimental fish in different substrate types was calculated.

[0022] Preferably, step 4 specifically includes: constructing and solving a two-dimensional shallow water hydrodynamic model based on the MIKE21 hydrodynamic simulation platform. This model is derived from the Navier-Stokes equations for incompressible fluids by integration in the depth direction, and its core governing equations specifically include the continuity equation: ; And the momentum equation in the x-direction: ; And the momentum equation in the y-direction:

[0023] In the above formula, x and y are used as the orthogonal spatial coordinates of the two-dimensional grid of the simulated region. Under the calculation time step t that satisfies the Cronbach's alpha stability, the instantaneous water depth h, water level Z, and vertical average flow velocities u and v along the x and y directions at the grid nodes are iteratively solved. The gravitational acceleration g in the formula is taken as a standard constant, and the eddy viscosity coefficient ν is used to describe the momentum exchange caused by the turbulent shear stress of the water flow. It is dynamically calculated by the Smagorinsky formula or calibrated by combining field experience. Its specific expression is as follows: ; In the formula , which is the Smagorinsky constant, used to adjust the magnitude of eddy viscosity at the subgrid scale, and its value is determined by calibration in combination with hydrological characteristics; For grid feature scale, Where A is the planar physical area of ​​the corresponding grid cell; the Manning roughness coefficient n, which characterizes the frictional resistance of the riverbed bottom, is not implemented using a single fixed value, but is strictly differentiated and discretely assigned according to the actual spatial distribution areas of the five typical bottom sediment types identified in the previous survey: silt, gravel, small and medium pebbles, smooth large rocks, and large rocks attached to the bottom sediment; after the preliminary hydrodynamic simulation is completed, the simulated water depth and flow velocity data at the aforementioned representative habitat monitoring points are extracted as simulated values. , and real physical data obtained on site The measured values ​​were compared one by one, and the data from the verification points were substituted into the root mean square error verification formula:

[0024] Calculations are performed, and when the root mean square error (RMSE) values ​​of the water depth and flow velocity are both lower than the preset reasonable error threshold, it is determined that the boundary conditions and Manning roughness coefficient parameters of the hydrodynamic model have been successfully calibrated. At this time, the output hydrodynamic parameters serve as reliable data support for the suitability evaluation of the Qinghai Lake naked carp spawning ground.

[0025] Preferably, in step 5, a weighted habitat suitability index model is used to evaluate habitat suitability. The model includes two parameters: the Habitat Suitability Index (HSI) and the Weighted Habitat Area (WUA). The HSI calculation expression is:

[0026] For the first i The suitability index of each environmental factor ranges from 0 to 1, where 0 indicates unsuitable and 1 indicates optimal. For the first i The weights of each environmental factor are assigned, and their magnitudes represent the degree of impact of that environmental factor on the species' habitat.

[0027] Preferably, the specific method for determining the suitability index (SI) of each individual habitat factor is as follows: Based on the habitat preference data of Qinghai Lake naked carp during the spawning period obtained from previous field surveys, including the frequency of fish occurrence and the corresponding physical habitat parameters, frequency analysis and normalization are used for derivation; specifically, the water depth or flow velocity of a certain environmental factor is divided into several intervals, and the interval with the highest recorded fish frequency is taken as the most suitable habitat, and its SI value is assigned as 1. The SI values ​​of the other intervals are equal to the ratio of the fish frequency in that interval to the highest frequency; for continuous variables, the above scattered data are subjected to polynomial nonlinear fitting to construct a continuous single-factor suitability curve; for discrete variables, the category normalization is directly performed based on the proportion of effective residence time of the experimental fish on different substrates in the microhabitat substrate preference experiment, so as to realize the accurate mapping of physical hydrological parameters to the biological suitability index in the range of 0~1; Based on the calculation results, the HSI is defined as follows: very suitable range is 0.8-1.0, suitable range is 0.6-0.8, moderately suitable range is 0.4-0.6, unsuitable range is 0.2-0.4, and very unsuitable range is 0-0.2. Based on the calculation of HSI, the habitat quality of the study area is quantitatively evaluated using weighted effective habitat area (WUA), and the calculation expression is as follows:

[0028] In the formula, Weighted effective habitat area; Indicates the first i Area of ​​each calculation unit; The basic hydrological data required to calculate the weighted effective habitat area of ​​Qinghai Lake naked carp under different flow conditions are all generated by the hydrodynamic model described in step 4 under the corresponding flow conditions. Specifically, the water depth and flow velocity data of each grid output by the hydrodynamic model are used as input parameters for evaluating habitat suitability, and then the effective habitat area is obtained by weighting.

[0029] The beneficial effects of this invention are as follows: The proposed method for assessing the suitability of spawning grounds for Qinghai Lake naked carp can provide theoretical support and engineering application suggestions for in-situ habitat restoration of Qinghai Lake naked carp, fully leveraging its protective role for Qinghai Lake naked carp and contributing to the protection of the Qinghai Lake ecological environment and Qinghai Lake naked carp population. It can also be applied to assess the suitability of spawning grounds for Qinghai Lake naked carp, providing data support and implementation direction for habitat restoration of Qinghai Lake naked carp. Attached Figure Description

[0030] Figure 1 This is a flowchart of the steps of the present invention; Figure 2These are 26 substrate conditions for this invention; Figure 3 This refers to the water depth threshold range for the 26 survey points in this invention; Figure 4 The flow velocity threshold ranges for the 26 survey points in this invention; Figure 5 This document presents the sex survey results of naked carp in Qinghai Lake at 26 survey sites as described in this invention. Figure 6 This is a map showing the distribution of river water depth under different working conditions in the research area of ​​this invention; Figure 7 This is a map showing the distribution of river flow velocity under different working conditions in the research area of ​​this invention; Figure 8 This is the suitability curve of the habitat environmental factors of the Qinghai Lake naked carp spawning grounds in the study area of ​​this invention; Figure 9 This is a map showing the distribution of suitable habitats for the naked carp of Qinghai Lake under different working conditions in the research area of ​​this invention. Detailed Implementation

[0031] Example 1: This proposal presents a method for assessing the suitability of Qinghai Lake naked carp spawning grounds. Based on existing engineering studies, it investigates habitat substrate, water depth, flow velocity, and sex. The entropy weight method is used to determine the weights of the habitat suitability ranking system for Qinghai Lake naked carp spawning in the Shaliu River. Weights are calculated for five indicators: water depth, flow velocity, substrate, pH, and dissolved oxygen. Based on the obtained weight values ​​and scores, the TOPSIS method is used to perform a ranking analysis of habitat suitability during the spawning period of the Qinghai Lake naked carp in the Shaliu River study section, determining the priority order of habitat suitability. Then, a habitat simulation pond for Qinghai Lake naked carp with five substrate types is constructed. The preference index quantification method is used to determine the preferred substrate type and preference intensity of male and female individuals. Based on this, a multi-factor interaction experiment is conducted to analyze the behavioral patterns of Qinghai Lake naked carp under different sexes, identifying the internal and external factors influencing substrate selection. The MIKE hydrodynamic model is used to simulate the hydrodynamics of the Qinghai Lake naked carp spawning grounds. Finally, the Habitat Suitability Index is used. The HSI (Homo erectus index) quantitatively describes the relationship between organisms' habitat preferences and habitat factors. The simulation results of the hydrodynamic model in step 4 of this invention are used as input for the Qinghai Lake naked carp habitat. The suitability-weighted effective habitat area of ​​the Qinghai Lake naked carp in the middle and lower reaches of the Shaliu River under different hydrological conditions during the Qinghai Lake naked carp's breeding migration period is calculated. Based on this, the habitat quality of the Qinghai Lake naked carp in the Shaliu River is assessed. The proposed method for assessing the suitability of Qinghai Lake naked carp spawning grounds can be applied to the suitability assessment of Qinghai Lake naked carp habitat, providing data support and implementation direction for habitat restoration. The specific steps are as follows: Step 1: Conduct a survey of the spawning grounds of naked carp in Qinghai Lake to obtain information on population distribution and habitat aquatic environmental factors; Step 2: Analyze the preference range and weight of each environmental factor to determine the priority level of spawning grounds; Step 3: Observe the behavioral response of Qinghai Lake naked carp through microhabitat simulation experiments to obtain the substrate selection preferences of the Qinghai Lake naked carp population; Step 4: Construct a hydrodynamic model of the evaluation area; Step 5: Construct an evaluation model for the habitat of the naked carp in Qinghai Lake, and evaluate the suitability of the habitat of the naked carp in Qinghai Lake in combination with a hydrodynamic model.

[0032] Preferably, in step 1, the method for investigating the spawning grounds of the Qinghai Lake naked carp is as follows: based on the migration and breeding season of the Qinghai Lake naked carp, a habitat survey is carried out in the study area, and survey points are selected to investigate the bottom sediment, flow velocity, water depth, and sex of the survey points.

[0033] Preferably, in step 2, the weight values ​​of each environmental factor are calculated using the entropy weight method.

[0034] Preferably, the weight values ​​of each environmental factor are calculated using the entropy weight method. The calculation steps are as follows: (1) Data matrix standardization, the standardization formula is:

[0035] In the formula For standardized indicator values, As the initial standard value, This is the maximum value of the indicator. This is the minimum value of this indicator; Standardize the data matrix.

[0036] (2) Calculation of index entropy value: The entropy of the i-th index is defined as:

[0037]

[0038] In the formula, k= , k is the Boltzmann constant, and n is the number of objects being evaluated; Let be the entropy value of the i-th index; This is the entropy value of the indicator.

[0039] (3) Calculation of indicator weights: Based on the indicator entropy value, the formula for calculating the weights of each indicator is as follows:

[0040] The entropy weight method is used to determine the index weights. ; (4) Calculation of indicator weight vector, the calculation formula is:

[0041] Preferably, in step 2, based on the obtained weight values ​​of environmental factors, the priority level of spawning grounds is analyzed using the TOPSIS integrated model.

[0042] Preferably, the specific process of analyzing the priority hierarchy of spawning grounds using the TOPSIS integrated model is as follows: Weighted decision matrix Sure:

[0043] In the formula For the indicator weight vector, Standardized indicator values; Positive and negative ideal values Sure: ;

[0044]

[0045] Positive and negative ideal distance calculate:

[0046]

[0047] Each object to be evaluated Evaluation reference value calculation:

[0048] Based on the calculation result F, the priority levels of each spawning ground are defined as follows: 0.3≤F<1 is the preferred type of suitable habitat, 0.2≤F<0.3 is the main type of suitable habitat, 0.1≤F<0.2 is the secondary type of suitable habitat, and F<0.1 is the alternative type of suitable habitat.

[0049] Preferably, in step 3, a circular trough internally equipped with detachable filter and drainage components is provided as a habitat substrate simulation pond. Five typical habitat substrates are arranged in sections at the bottom of the simulation pond, specifically including: mud and sand with a diameter no greater than 0.01 cm, gravel with a diameter of 0.1 to 0.2 cm, small to medium-sized pebbles with a diameter of 2 to 5 cm, large pebbles and stones with a diameter of 10 to 25 cm and smooth surfaces, and large pebbles and stones with a diameter of 10 to 25 cm and a natural bottom mud layer on their surface. The fish to be tested are moved into the simulation pond containing the above five substrates to conduct a substrate preference test. Fish behavior is continuously recorded by an underwater camera, and the video activity is then processed using automatic frame-segmentation and tracking technology. Specifically, the continuous video stream is parsed into a sequence of single-frame images at a set frame rate. An image recognition algorithm is used to extract the spatial coordinates of the experimental fish in each frame. These spatial coordinates are then compared with the boundaries of five pre-defined substrate regions to determine the substrate type in each frame. Finally, by accumulating the total number of frames in which the experimental fish appear in each substrate region and combining this with the set frame rate, the actual dwell time of the experimental fish in different substrate types is calculated.

[0050] Preferably, in step 4, the two-dimensional shallow water hydrodynamic model is constructed and solved using the MIKE 21 hydrodynamic simulation platform. This model is derived from the Navier-Stokes equations for incompressible fluids by integration in the depth direction, and its core governing equations specifically include the continuity equation:

[0051] And the momentum equation in the x-direction:

[0052] And the momentum equation in the y-direction:

[0053] In the above formula, x and y are used as the orthogonal spatial coordinates of the two-dimensional grid of the simulated region. Under the calculation time step t that satisfies the Cronbach's alpha stability, the instantaneous water depth h, water level Z, and vertical average flow velocities u and v along the x and y directions at the grid nodes are iteratively solved. The gravitational acceleration g in the formula is taken as a standard constant, and the eddy viscosity coefficient ν is used to describe the momentum exchange caused by the turbulent shear stress of the water flow. It can be dynamically calculated by the Smagorinsky formula or calibrated by combining field experience. Its specific expression is as follows:

[0054] In the formula , denoted by Smagorinsky constant, is used to adjust the magnitude of eddy viscosity at the subgrid scale. In this embodiment, its value can be calibrated based on the hydrological characteristics of the Shaliu River. Simultaneously, the Manning roughness coefficient n, which characterizes the frictional resistance of the riverbed flow, is not implemented using a single fixed value. Instead, it is assigned differentially and discretely based on the actual spatial distribution areas of the five typical substrate types (silt, gravel, small and medium pebbles, smooth large rocks, and sediment-attached large rocks) identified in the previous survey. Since different substrate particle sizes have different water-blocking effects, this refined parameter distribution based on substrate type greatly improves the realism of the microhabitat benthic flow field simulation. After the initial hydrodynamic simulation is completed, the simulated water depth and velocity data at the aforementioned 26 representative habitat monitoring points are extracted as the simulated value Si, which is then compared with the actual physical data obtained from the field. The data from these 26 verification points (total sample size N=26) were compared one by one with the measured values, and then substituted into the root mean square error verification formula:

[0055] Calculations are performed, and when the root mean square error (RMSE) values ​​of water depth and flow velocity are both lower than the preset reasonable error threshold, it is determined that the boundary conditions and parameters such as the Manning roughness coefficient of the substrate of the hydrodynamic model have been successfully calibrated. At this time, the output hydrodynamic parameters can serve as reliable data support for the suitability evaluation of the spawning grounds of naked carp in Qinghai Lake.

[0056] Preferably, in step 5, a weighted habitat suitability index model is used to evaluate habitat suitability. The model includes two parameters: the Habitat Suitability Index (HSI) and the Weighted Habitat Area (WUA). The HSI calculation expression is:

[0057] Let be the suitability index of the i-th environmental factor, and its value ranges from 0 to 1, where 0 indicates unsuitable and 1 indicates optimal. Assign a weight to the i-th environmental factor, the magnitude of which represents the degree of impact of the environmental factor on the species' habitat.

[0058] The specific method for determining the suitability index (SI) of each individual habitat factor is as follows: Based on the habitat preference data of naked carp during the spawning period in Qinghai Lake (including the frequency of fish occurrence and corresponding physical habitat parameters) obtained from previous field surveys, frequency analysis and normalization are used for derivation. Specifically, a certain environmental factor (such as water depth or flow velocity) is divided into several intervals, and the interval with the highest recorded fish frequency is taken as the most suitable habitat, with its SI value assigned to 1. The SI values ​​of other intervals are equal to the ratio of the fish frequency in that interval to the highest frequency. For continuous variables (water depth, flow velocity), the above scattered data are subjected to polynomial nonlinear fitting to construct a continuous single-factor suitability curve. For discrete variables (such as five types of typical substrates), the category normalization is directly assigned based on the proportion of effective residence time of experimental fish on different substrates in the microhabitat substrate preference experiment, thereby realizing the accurate mapping of physical hydrological parameters to biological suitability indices in the range of 0 to 1.

[0059] Based on the calculation results, the HSI is defined as follows: very suitable range is 0.8-1.0 (including the upper limit but excluding the lower limit, the same below), suitable range is 0.6-0.8, moderately suitable range is 0.4-0.6, unsuitable range is 0.2-0.4, and very unsuitable range is 0-0.2.

[0060] Based on the calculation of HSI, the habitat quality of the study area is quantitatively evaluated using weighted effective habitat area (WUA), and the calculation expression is as follows:

[0061] In the formula, Weighted effective habitat area; This represents the area of ​​the i-th computational unit; The basic hydrological data required to calculate the weighted effective habitat area of ​​Qinghai Lake naked carp under different flow conditions are all generated by the hydrodynamic model described in step 4 under the corresponding flow conditions. Specifically, the water depth and flow velocity data of each grid output by the hydrodynamic model are used as input parameters for evaluating habitat suitability, and then the effective habitat area is obtained by weighting.

[0062] Example 2: Taking the adaptive evaluation of the spawning grounds of the naked carp in Qinghai Lake as an example, a calculation example is provided to specifically illustrate the calculation method and process involved in this invention. The determination process is as follows: 1. Based on the typical geomorphological features of Qinghai Lake naked carp habitats (deep pools, shallow shoals, deep pools, shallow currents, etc.) and the presence of fish eggs, 26 habitats were selected from 70 monitoring points. The survey results of substrate, water depth, current velocity, and sex of these habitats are shown in […]. Figure 2 , Figure 3 , Figure 4, Figure 5 .

[0063] 2. The weights of the habitat suitability ranking system were determined by the entropy weight method, as shown in Table 1. The relative importance, from largest to smallest, is as follows: water depth, current velocity, substrate, dissolved oxygen, and pH. The weights calculated by the entropy weight method are summarized in Table 1.

[0064] Table 1 Summary of weight calculation results using the entropy method

[0065] Based on the obtained weight values, the TOPSIS method was used to determine the priority order of habitat suitability during the spawning period of the Qinghai Lake naked carp in the Shaliu River study section. The TOPSIS evaluation calculation results are shown in Table 2.

[0066] Table 2 TOPSIS Evaluation Calculation Results

[0067] Steps 1 and 2 aim to reveal the characteristics and features of the spawning habitat of *Gymnocypris qinghai Lake* through investigation, providing a basis for subsequent habitat suitability assessment. A detailed investigation was conducted on environmental factors such as substrate, water depth, and current velocity, as well as the sex composition of fish populations in the study area and spawning grounds. Based on this, the spawning grounds of *Gymnocypris qinghai Lake* in the Shaliu River section were analyzed and summarized. Finally, the suitability priority assessment system for the spawning habitat of *Gymnocypris qinghai Lake* in the Shaliu River section was used to determine the suitability priority level of each habitat.

[0068] 3. The microhabitat simulation device was a habitat substrate simulation pond, a circular rubber tank with a diameter of 2.3m and a depth of 0.6m. The tank was equipped with a removable filter and drainage system. Experiments showed significant differences in substrate visit time between males and females under different substrate types. The total visit time for females across different substrate types was ranked as follows: gravel > small to medium pebbles > mud > smooth substrate (large pebbles and rocks) > mud-attached substrate (large pebbles and rocks). Females spent significantly more time on gravel substrates than on other substrates (P<0.05). For males, the total visit time across different substrate types was ranked as follows: small to medium pebbles > gravel > mud-attached substrate (large pebbles and rocks) > mud > smooth substrate (large pebbles and rocks). Males spent significantly more time on small to medium pebbles, gravel, and mud-attached substrate (large pebbles and rocks) than on other substrate types.

[0069] 4. During the hydrodynamic simulation, topographic data of the study area was acquired using UAVs to obtain the riverbed and channel morphology of the study section. The channel topographic data was obtained through the fusion of GPS measurement and data transmission technologies, ultimately yielding 3211 precise topographic scatter points with required elevations and coordinates, which served as the boundary conditions for the hydrodynamic simulation. Then, SMS software was used to generate a mesh. Due to the irregular topographic boundaries of the study area, an unstructured triangular mesh was used to divide the topography. Simulations were performed on meshes that did not meet the conditions. The mesh was then imported into MIKEZERO for editing and defining boundary conditions. Based on the actual site conditions, the main parameter was set to a roughness coefficient of 32m according to the Manning formula. 1 / 3 / s, time step 30s, dry and wet boundaries set to Dry depth 0.005m, Flooding depth 0.05m, Wetting depth 0.1m, eddy viscosity coefficient set to 0.28m. 2 / s. To ensure the accuracy of the calculation results, a river flow rate of 6.92 m³ / s was selected. 3 Under the hydrological conditions of / s, the measured flow velocity data at the end section of the studied river segment were compared with the simulation results. The average absolute error was found to be 0.01 m / s, and the maximum error was 0.08 m / s. The relatively small errors indicate that the hydrodynamic model design in this study is reasonable. The hydrodynamic simulation results for the flow field characteristics under five working conditions are as follows: Figure 6 , Figure 7 .

[0070] 5. In the assessment of habitat suitability for *Gymnocypris qinghai Lake*, the primary substrate type was recorded twice, and the secondary substrate type was recorded once. It was found that small and medium-sized pebbles and gravel appeared most frequently in the spawning grounds surveyed previously, reaching 34 and 18 times respectively. Their overall substrate preference trend is consistent with the results of the *Gymnocypris qinghai Lake* substrate preference experiment. Regarding flow velocity, the most frequent velocity range was 0-0.2 m / s, accounting for 76.32% of the total, with the highest frequency occurring in the 0-0.1 m / s range, totaling 22 times. Regarding water depth, the most frequent water depth range for *Gymnocypris qinghai Lake* was 2-30 cm, accounting for 88% of the total, with the highest frequency occurring in the 2-10 cm depth range, totaling 22 times. Here, the suitability value of the most frequently occurring small and medium-sized pebble substrate in the field survey was assigned as 1.0, and the other substrate types were assigned values ​​in order of frequency of occurrence. For flow velocity, the range of 0.1 m / s, which had the highest frequency, was assigned a value of 1.0. For water depth, the range of 2-10 cm, which had the highest frequency, was assigned a value of 1.0. Other water depths were normalized according to their frequency of occurrence. Since the experimental fish data showed that the body height of the Qinghai Lake naked carp was around 2 cm, water depths below 2 cm were assigned a value of 0. The suitability curves for substrate, flow velocity, and water depth of the Qinghai Lake naked carp spawning grounds in the study area are shown in [reference needed]. Figure 8 .

[0071] This embodiment selects five typical flow rates as simulated conditions for the spawning grounds of *Naked Carp qinghai Lake* in the Shaliu River study area for analysis. The effective habitat area of ​​the *Naked Carp qinghai Lake* spawning grounds under the five flow rate conditions is statistically analyzed. The highest relative habitat area ratio is observed at a flow rate of 4.2 m³ / s, reaching 37.08%. When the flow rate reaches 10 m³ / s... 3 At a flow rate of / s, the relative habitat area was the lowest, at 26.64%. The weighted habitat area under different flow rates is shown in Table 3.

[0072] Table 3 Weighted habitat area under different flow rates

[0073] By calculating the comprehensive HSI value of the spawning grounds of *Gymnocypris qinghai Lake* and combining it with a hydrodynamic model, a distribution map of suitable habitats for *Gymnocypris qinghai Lake* under typical flow conditions in the Shaliu River study area was drawn. The distribution map was drawn when the flow rate was 4.2 m³ / s. 3 At a flow rate of 2.31 m³ / s, the area of ​​highly suitable habitats with an HSI value greater than 0.8 is the largest, mainly concentrated on both banks of the riverbed and in meandering sections. 3 At a flow rate of / s, the area of ​​suitable habitat is the second largest; as the flow rate exceeds the suitable hydraulic conditions for the habitat of the Qinghai Lake naked carp, the area of ​​unsuitable habitat increases significantly, and high-quality habitats are mainly distributed in deep pools, river islands, and exposed mudflats under low flow rates. The HSI values ​​of spawning grounds under different working conditions are shown in the figure. Figure 9 .

[0074] The above embodiments are merely preferred technical solutions of the present invention and should not be considered as limitations on the present invention. The scope of protection of the present invention should be limited to the technical solutions described in the claims, including equivalent substitutions of the technical features described in the claims. That is, equivalent substitutions and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A method for evaluating the suitability of spawning grounds for Qinghai Lake naked carp, characterized in that, Includes the following steps: Step 1: Conduct a survey of the spawning grounds of naked carp in Qinghai Lake to obtain information on population distribution and habitat aquatic environmental factors; Step 2: Analyze the preference range and weight of each environmental factor to determine the priority level of spawning grounds; Step 3: Observe the behavioral response of Qinghai Lake naked carp through microhabitat simulation experiments to obtain the substrate selection preferences of the Qinghai Lake naked carp population; Step 4: Construct a hydrodynamic model of the evaluation area; Step 5: Construct an evaluation model for the habitat of the naked carp in Qinghai Lake, and evaluate the suitability of the habitat of the naked carp in Qinghai Lake in combination with a hydrodynamic model.

2. The method for evaluating the suitability of spawning grounds for Qinghai Lake naked carp according to claim 1, characterized in that, In step 1, the method for investigating the spawning grounds of the Qinghai Lake naked carp is as follows: based on the migration and breeding season of the Qinghai Lake naked carp, a habitat survey is carried out in the study area, and survey points are selected to investigate the bottom sediment, flow velocity, water depth, and sex of the survey points.

3. The method for evaluating the suitability of spawning grounds for *Gymnocypris qinghai Lake* according to claim 1, characterized in that, In step 2, the weight values ​​of each environmental factor are calculated using the entropy weight method.

4. The method for evaluating the suitability of spawning grounds for Qinghai Lake naked carp according to claim 3, characterized in that, The weight values ​​of each environmental factor are calculated using the entropy weight method. The calculation steps are as follows: (1) Data matrix standardization, the standardization formula is: In the formula For standardized indicator values, As the initial standard value, This is the maximum value of the indicator. This is the minimum value of this indicator; Standardized indicator values; (2) Calculation of index entropy value: The entropy of the i-th index is defined as: In the formula, k= , k is the Boltzmann constant, and n is the number of objects being evaluated; Let be the entropy value of the i-th index; The entropy value of the indicator; (3) Calculation of indicator weights: Based on the indicator entropy value, the formula for calculating the weights of each indicator is as follows: The entropy weight method is used to determine the index weights. ; (4) Calculation of indicator weight vector, the calculation formula is: 。 5. The method for evaluating the suitability of spawning grounds for Qinghai Lake naked carp according to claim 4, characterized in that, In step 2, based on the obtained weight values ​​of environmental factors, the priority level of spawning grounds is analyzed using the TOPSIS integrated model.

6. The method for evaluating the suitability of spawning grounds for *Gymnocypris qinghai Lake* according to claim 5, characterized in that, The specific process of using the TOPSIS integrated model to analyze the priority hierarchy of spawning grounds is as follows: Weighted decision matrix Sure: In the formula For the indicator weight vector, Standardized indicator values; Positive and negative ideal values Sure: ； Positive and negative ideal distance calculate: Each object to be evaluated Evaluation reference value calculation: Based on the calculation result F, the priority levels of each spawning ground are defined as follows: 0.3≤F<1 is the preferred type of suitable habitat, 0.2≤F<0.3 is the main type of suitable habitat, 0.1≤F<0.2 is the secondary type of suitable habitat, and F<0.1 is the alternative type of suitable habitat.

7. The method for evaluating the suitability of spawning grounds for Qinghai Lake naked carp according to claim 1, characterized in that, Step 3 specifically involves: providing a circular tank equipped with detachable filter and drainage components as a habitat substrate simulation pond; dividing the bottom of the simulation pond into zones and arranging five typical habitat substrates, specifically including: mud and sand with a diameter no greater than 0.01 cm, gravel with a diameter of 0.1 to 0.2 cm, small to medium-sized pebbles with a diameter of 2 to 5 cm, large pebbles and stones with a diameter of 10 to 25 cm and smooth surfaces, and large pebbles and stones with a diameter of 10 to 25 cm and a natural bottom mud layer on the surface; transferring the fish to be tested into the simulation pond containing the above five substrates to conduct a substrate preference test, the test stage... The process involves continuously recording fish behavior using an underwater camera; then processing the video using automatic frame-segmentation and tracking technology. Specifically, the continuous video stream is parsed into a sequence of single-frame images at a set frame rate. An image recognition algorithm is used to extract the spatial coordinates of the experimental fish in each frame, and these coordinates are compared with the boundaries of five pre-defined substrate regions to determine the substrate type in each frame. Finally, by accumulating the total number of frames in which the experimental fish appear in each substrate region and combining this with the set frame rate, the actual dwell time of the experimental fish in different substrate types is calculated.

8. The method for evaluating the suitability of spawning grounds for Qinghai Lake naked carp according to claim 1, characterized in that, Step 4 specifically includes: constructing and solving a two-dimensional shallow water hydrodynamic model based on the MIKE21 hydrodynamic simulation platform. This model is derived by integrating the Navier-Stokes equations for incompressible fluids in the depth direction. Its core governing equations specifically include the continuity equation: ； And the momentum equation in the x-direction: ； And the momentum equation in the y-direction: In the above formula, x and y are used as the orthogonal spatial coordinates of the two-dimensional grid of the simulated region. Under the calculation time step t that satisfies the Cronbach's alpha stability, the instantaneous water depth h, water level Z, and vertical average flow velocities u and v along the x and y directions at the grid nodes are iteratively solved. The gravitational acceleration g in the formula is taken as a standard constant, and the eddy viscosity coefficient ν is used to describe the momentum exchange caused by the turbulent shear stress of the water flow. It is dynamically calculated by the Smagorinsky formula or calibrated by combining field experience. Its specific expression is as follows: ； In the formula , which is the Smagorinsky constant, used to adjust the magnitude of eddy viscosity at the subgrid scale, and its value is determined by calibration in combination with hydrological characteristics; For grid feature scale, Where A is the planar physical area of ​​the corresponding grid cell; the Manning roughness coefficient n, which characterizes the frictional resistance of the riverbed bottom, is not implemented using a single fixed value, but is strictly differentiated and discretely assigned according to the actual spatial distribution areas of the five typical bottom sediment types identified in the previous survey: silt, gravel, small and medium pebbles, smooth large rocks, and large rocks attached to the bottom sediment; after the preliminary hydrodynamic simulation is completed, the simulated water depth and flow velocity data at the aforementioned representative habitat monitoring points are extracted as simulated values. , and real physical data obtained on site The measured values ​​were compared one by one, and the data from the verification points were substituted into the root mean square error verification formula: Calculations are performed, and when the root mean square error (RMSE) values ​​of the water depth and flow velocity are both lower than the preset reasonable error threshold, it is determined that the boundary conditions and Manning roughness coefficient parameters of the hydrodynamic model have been successfully calibrated. At this time, the output hydrodynamic parameters serve as reliable data support for the suitability evaluation of the Qinghai Lake naked carp spawning ground.

9. The method for evaluating the suitability of spawning grounds for Qinghai Lake naked carp according to claim 1, characterized in that, In step 5, a weighted habitat suitability index model is used to evaluate habitat suitability. The model includes two parameters: the Habitat Suitability Index (HSI) and the Weighted Habitat Area (WUA). The HSI calculation expression is as follows: For the first i The suitability index of each environmental factor ranges from 0 to 1, where 0 indicates unsuitable and 1 indicates optimal. For the first i The weights of each environmental factor are assigned, and their magnitudes represent the degree of impact of that environmental factor on the species' habitat.

10. The method for evaluating the suitability of spawning grounds for *Gymnocypris qinghai Lake* according to claim 9, characterized in that, The specific method for determining the suitability index (SI) of each individual habitat factor is as follows: Based on the habitat preference data of naked carp during the spawning period in Qinghai Lake obtained from previous field surveys, including the frequency of fish occurrence and the corresponding physical habitat parameters, frequency analysis and normalization are used for derivation; specifically, the water depth or flow velocity of a certain environmental factor is divided into several intervals, and the interval with the highest recorded fish frequency is taken as the most suitable habitat, and its SI value is assigned as 1. The SI value of each other interval is equal to the ratio of the fish frequency in that interval to the highest frequency; for continuous variables, the above scattered data are fitted with a polynomial nonlinearity to construct a continuous single-factor suitability curve; for discrete variables, the category normalization is directly performed based on the proportion of effective residence time of experimental fish on different substrates in the microhabitat substrate preference experiment, so as to achieve accurate mapping of physical hydrological parameters to biological suitability indices in the range of 0 to 1; Based on the calculation results, the HSI is defined as follows: very suitable range is 0.8-1.0, suitable range is 0.6-0.8, moderately suitable range is 0.4-0.6, unsuitable range is 0.2-0.4, and very unsuitable range is 0-0.

2. Based on the calculation of HSI, the habitat quality of the study area is quantitatively evaluated using weighted effective habitat area (WUA), and the calculation expression is as follows: In the formula, Weighted effective habitat area; Indicates the first i Area of ​​each calculation unit; The basic hydrological data required to calculate the weighted effective habitat area of ​​Qinghai Lake naked carp under different flow conditions are all generated by the hydrodynamic model described in step 4 under the corresponding flow conditions. Specifically, the water depth and flow velocity data of each grid output by the hydrodynamic model are used as input parameters for evaluating habitat suitability, and then the effective habitat area is obtained by weighting.

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