Evaluation method for dynamic suitability of fish habitat

Abstract

The invention discloses a method for evaluating the dynamic suitability of a fish habitat, which considers the characteristic that habitat habitat factors such as annual non-constant water depth, flow velocity and water temperature of a river have dynamic changes, and evaluates the dynamic suitability of the fish habitat according to a dynamic response curve of fish habitat suitability to habitat factor changes. Calculating the suitability of each region in the river and the change process of the weighted available area in the year, on this basis, counting the suitable days of each region in the river in the fish spawning stage, calculating the time satisfaction coefficient in the suitability interval and the duration days of the suitable time, and describing the change curve of the dynamic suitability total area in the year. According to the calculation method, the adaptability of the fish spawning stage to the river in the whole year can be more reasonably evaluated, so that the operation of ecological scheduling is more scientifically guided.

Description

Technical Field

[0001] The invention relates to the technical field of ecohydraulics, and in particular to a method for evaluating the dynamic suitability of fish habitats. Background Art

[0002] my country's rivers are highly developed and utilized. A large number of water conservancy projects have changed the hydrological and ecological conditions of natural rivers, resulting in a decline in the quality of physical habitats and a reduction in biodiversity. With the increasing awareness of ecological protection, ensuring the ecological flow of rivers has become a basic requirement for the preliminary design of water conservancy projects and an important basis for ensuring the health and sustainable development of river ecosystems.

[0003] In the existing habitat suitability assessment methods, the effects of the physical, chemical and biological characteristics of rivers on the habitats of indicator species are studied by designing constant working conditions, thereby obtaining the scope and quality of suitable habitats for fish at different life history stages. In reality, rivers flow non-constantly throughout the year, and the selection of fish for habitats such as spawning grounds is a dynamic assessment. Studies have shown that the spawning process of fish requires continuous and appropriate stimulation of water depth, flow rate and water temperature. However, the current habitat model does not take into account the effects of non-constant flow in rivers throughout the year, and does not calculate the dynamic suitability of habitats. The results obtained are difficult to reflect the adaptability of fish spawning grounds to the non-constant water flow and water temperature of rivers throughout the year, especially during the spawning period, and the scientific nature of ecological scheduling needs to be further improved.

[0004] In summary, the present invention provides a method for evaluating the dynamic suitability of fish habitats, aiming to solve the above problems. Summary of the invention

[0005] The purpose of the present invention is to provide a method for evaluating the dynamic suitability of fish habitats, so as to more reasonably evaluate the adaptability of fish to the non-constant flow of rivers throughout the year during the spawning stage, thereby more scientifically guiding the operation of ecological scheduling.

[0006] To achieve the above invention objectives, the technical solution adopted by the present invention is a method for evaluating the dynamic suitability of fish habitats, comprising the following steps:

[0007] S1: Establish a habitat dynamic model based on the study area and target fish spawning grounds;

[0008] S2: using the habitat dynamic model, dividing the river into triangular grids, taking each grid as a unit, setting the actual or designed non-constant flow process of the river, and calculating the dynamic suitability value of the habitat index of each unit under the non-constant flow process, wherein the habitat index includes water depth h, flow velocity v and water temperature T;

[0009] S3: Multiply the dynamic suitability values ​​of each habitat indicator to obtain the comprehensive dynamic suitability of the unit habitat;

[0010] S4: Count the number of days when the comprehensive dynamic suitability of the unit habitat meets the suitability interval (0,1) of the spawning ground habitat factors, and calculate the unit habitat time satisfaction coefficient based on the statistical number of days. The unit habitat time satisfaction coefficient is used to evaluate whether the unit is suitable for spawning of target fish for a long time;

[0011] S5: Record the start and end dates of the unit habitat's comprehensive suitability in the suitability interval, and count the number of days that it can be continuously in the suitability interval to evaluate whether the unit can continue to be suitable for target fish spawning. The greater the number of continuous days, the more suitable the area is for fish spawning under non-constant flow;

[0012] S6: Calculate the total dynamic suitable area of ​​fish spawning habitats, and combine it with the non-constant flow process Qt to establish the time series t-dynamic suitability total area HAS curve of fish habitats throughout the year, and then evaluate whether the entire river is suitable for fish spawning under non-flow processes.

[0013] Furthermore, the step S1 specifically includes:

[0014] (1.1) Determine the target fish species based on the study area and select the habitat factors of the spawning grounds; conduct a survey of the target fish species, record the habitat factors of the spawning grounds of the target fish species, and collect continuous long-sequence data of the spawning grounds of the target fish species;

[0015] (1.2) Conduct experimental research on target fish in the laboratory to obtain the relationship between target fish and habitat factors during the spawning stage, and obtain the suitability curve of each habitat factor during the spawning stage of target fish;

[0016] (1.3) Establish a hydrodynamic-water temperature model for the study area to simulate the dynamic changes of hydrodynamic and water temperature indicators in the river sections where the target species’ habitats are located;

[0017] (1.4) Based on the suitability curve of habitat factors during the fish spawning stage obtained from experimental research, and using the hydrodynamic and water temperature changes calculated by the hydrodynamic-water temperature model as the boundary, complete the modeling of the habitat dynamics model of the target fish spawning ground.

[0018] Furthermore, step (1.3) specifically includes:

[0019] (1.3.1) Collect data in the research area, collect underwater topography, hydrology, and water temperature data, and organize and analyze the hydrological and water temperature conditions of characteristic hydrological years;

[0020] (1.3.2) Establish a hydrodynamic model for the study area and simulate the changes in the hydrodynamic indicators of the unsteady flow in the area;

[0021] (1.3.3) Establish a water temperature model for the study area and simulate the changes in non-steady flow water temperature in the area.

[0022] Furthermore, the step S2 specifically includes:

[0023] (2.1) Divide the river into grids, take each grid area as a unit, and calculate the temporal changes of various habitat indicators of each unit under the non-constant flow process in a typical year of the river;

[0024] (2.2) Using the habitat dynamic model, the dynamic suitability values ​​of the unit spawning ground habitat factors water depth h, flow velocity v and water temperature T in the non-steady flow are calculated respectively,

[0025] Furthermore, in step S3, the following formula is used to calculate the comprehensive dynamic suitability of the unit habitat:

[0026]

[0027] Where: is the comprehensive dynamic suitability of habitat in unit i, t is a certain moment in the year, s, They are the dynamic suitability of flow velocity, water depth and water temperature of unit i respectively.

[0028] Furthermore, the step S4 specifically includes:

[0029] (4.1) Taking grid cells as units, the number of days in a year when the water depth, flow velocity, and water temperature of unit i simultaneously meet the suitability interval (0, 1) of the spawning habitat factors is counted, denoted as T di ; The total number of days of fish spawning stage is recorded as T t ;

[0030] (4.2) Taking the grid unit as the unit, the unit habitat time satisfaction coefficient is calculated using the following formula:

[0031]

[0032] Where: TS i is the unit habitat time satisfaction coefficient, with a value range of [0,1]. The larger the value, the longer the habitat suitability time is satisfied in the non-steady flow state, and the better the dynamic adaptability of the unit area to fish spawning.

[0033] Furthermore, the step S5 specifically includes:

[0034] (5.1) Record the start and end dates when the comprehensive suitability of the unit habitat is within the suitability interval (0-1], that is, the date when the unit area is suitable for fish spawning under the non-constant flow;

[0035] (5.2) The number of consecutive days that unit i is in the suitability interval is counted. The more days, the longer the time that can continuously adapt to fish spawning under the non-constant flow.

[0036] Further, step S6 specifically includes the following steps:

[0037] (6.1) Use the following formula to calculate the total dynamic suitable area of ​​fish spawning grounds:

[0038]

[0039] Where: HSA is the total dynamic suitable area of ​​the spawning ground; A i is the area of ​​unit i;

[0040] (6.2) According to the non-steady flow process of S2, the time series-flow curve and the flow-dynamic suitability total area curve obtained by the above formula are recorded to establish the time series-dynamic suitability total area curve of fish habitat;

[0041] (6.3) Based on the time series-dynamic suitability total area curve, the dynamic adaptability of the entire river to the spawning of target fish under non-flow conditions can be evaluated. The larger the total area, the better the adaptability of the fish under this flow.

[0042] The present invention has the following beneficial effects: the present invention takes into account the dynamic change characteristics of habitat factors such as annual non-constant water depth, flow velocity, and water temperature of the river, and calculates the change process of the suitability of each area in the river and the weighted available area in the year according to the dynamic response curve of the fish habitat suitability to the change of habitat factors. On this basis, the number of days suitable for fish spawning in each area of ​​the river is counted, the time satisfaction coefficient and the number of consecutive days in the suitability interval are calculated, and the annual change curve of the total area of ​​dynamic suitability is drawn. Through the above calculation method, the adaptability of fish spawning to the river throughout the year can be more reasonably evaluated, thereby more scientifically guiding the operation of ecological scheduling. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 A flow chart of a method for evaluating the dynamic suitability of fish habitats according to the present invention;

[0044] Figure 2 This is the grid division map of the river area;

[0045] Figure 3 is the change curve of habitat factors of unit i (h~t, v~t, T~t);

[0046] Figure 4 The habitat suitability curve (HSI) of a fish V ~V, HSI H~H、HSI T ~T);

[0047] Figure 5 is the dynamic suitability curve of habitat factors for unit i

[0048] Figure 6 is the comprehensive dynamic suitability value curve of unit i

[0049] Figure 7 It is a schematic diagram of the dynamic curve of total area of ​​time-dynamic fitness of fish. DETAILED DESCRIPTION

[0050] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings.

[0051] The present invention provides a method for evaluating the dynamic suitability of fish habitats, specifically: Figure 1 As shown in the figure, considering the dynamic change of habitat factors such as non-constant water depth, flow velocity, and water temperature in the river, the annual change process of the suitability of each area in the river and the weighted available area is calculated according to the dynamic response curve of the fish habitat suitability to the change of habitat factors. On this basis, the number of days suitable for fish spawning in each area of ​​the river is counted, the time satisfaction coefficient and the number of consecutive days in the suitability interval are calculated, and the annual change curve of the total area of ​​dynamic suitability is drawn, which includes the following steps:

[0052] S1: Establish a habitat dynamic model based on the study area and target fish spawning grounds;

[0053] (1.1) Determine the target fish species based on the ecosystem of the study area and select the habitat factors of the spawning grounds; conduct a survey of the target fish species, record the time, location, area, water depth, flow rate, water temperature and other habitat factors of the target fish spawning grounds, and collect continuous long-sequence data of the target fish spawning grounds;

[0054] A section of the Yangtze River Basin was selected as the research area. Combined with the regional fish survey in recent years, a rare fish species was selected as a representative of fish species that lay drifting eggs. This fish species has a specific requirement for spawning grounds, and the eggs need to drift and hatch. The water depth, flow rate, water temperature and other habitat factors of the spawning grounds of this fish species were recorded.

[0055] (1.2) Conduct experimental research on target fish in the laboratory to obtain the relationship between target fish during the spawning stage and habitat factors such as water depth, flow rate, and water temperature, and obtain the suitability curve between target fish during the spawning stage and habitat factors;

[0056] There have been many studies on the suitability curve of habitat factors for this fish. This time, the existing suitability curve of flow velocity, water depth and water temperature for this fish is used, such as Figure 3 shown.

[0057] (1.3) Establish a hydrodynamic-water temperature model for the study area to simulate the dynamic changes of hydrodynamic and water temperature indicators in the river section where the target species habitat is located; Step (1.3) specifically includes:

[0058] (1.3.1) Collect data in the research area, collect underwater topography, hydrology, and water temperature data, and organize and analyze the hydrological and water temperature conditions of characteristic hydrological years;

[0059] (1.3.2) Establish a hydrodynamic model for the study area and simulate the changes in the hydrodynamic indicators of the unsteady flow in the area;

[0060] (1.3.3) Establish a water temperature model for the study area to simulate the changes in water temperature of non-steady flow in the area;

[0061] The rivers in the study area are gridded, such as Figure 2 As shown. Using a two-dimensional hydrodynamic and water temperature model, the annual inflow process of regional rivers is used as the boundary to simulate the change process of water depth, flow velocity, and water stability of non-steady flow. Taking a unit i as an example, the simulation results of flow velocity, water depth, and water temperature are shown in Figure 4 shown.

[0062] (1.4) Establish a habitat dynamic model for the target fish spawning grounds: Based on the habitat factor suitability curve for the fish spawning stage obtained from experimental research, and with the hydrodynamic and water temperature changes calculated by the hydrodynamic-water temperature model as the boundary, complete the modeling of the habitat dynamic model for the target fish spawning grounds.

[0063] S2: using the habitat dynamic model, dividing the river into triangular grids, taking each grid as a unit, setting the actual or designed non-constant flow process of the river, and calculating the dynamic suitability values ​​of habitat indicators such as water depth h, flow velocity v, and water temperature T of each unit under the non-constant flow process, which are used for the subsequent calculation of the comprehensive dynamic suitability of the unit habitat; step S2 specifically includes:

[0064] (2.1) Divide the river into grids, take each grid area as a unit, and calculate the temporal changes of habitat indicators (water depth h, flow velocity v, water temperature T) of each unit under the non-constant flow process in a typical year of the river;

[0065] (2.2) Using the habitat dynamics model in (1.4), the dynamic suitability of the unit spawning ground habitat factors water depth h, flow velocity v and water temperature T in the non-steady flow is recorded as follows:

[0066]

[0067] The habitat dynamics model established in step (1.4) is used to calculate the dynamic suitability of the habitat factors of the spawning grounds of the river unit. Taking a unit i as an example, the dynamic suitability curve of the calculated habitat factors is as follows: Figure 5 shown.

[0068] S3: Multiply the dynamic suitability values ​​of each habitat indicator to obtain the comprehensive dynamic suitability of the unit habitat; specifically, taking the grid unit as the unit, the following formula is used to calculate the comprehensive dynamic suitability of the unit:

[0069]

[0070] Where: is the comprehensive dynamic suitability of habitat in unit i, t is a certain moment in the year, s, They are the dynamic suitability of flow velocity, water depth and water temperature of unit i respectively.

[0071] The above formula is further used to calculate the comprehensive dynamic suitability of river units. Taking a unit i as an example, the calculated comprehensive dynamic suitability curve is as follows: Figure 6 shown.

[0072] S4: Count the number of days when the comprehensive dynamic suitability of the unit habitat meets the suitability interval (0,1] of the spawning ground habitat factor, and calculate the unit habitat time satisfaction coefficient based on the counted number of days to evaluate whether the unit can be suitable for spawning of target fish for a long time; Step S4 specifically includes:

[0073] (4.1) Taking grid cells as units, the number of days in a year when the water depth, flow velocity, water temperature and other factors of unit i are simultaneously in the suitability interval of the spawning ground habitat factors is counted, denoted as T di ; The total number of days of fish spawning stage is recorded as T t ;

[0074] (4.2) Taking the grid unit as the unit, the unit habitat time satisfaction coefficient is calculated using the following formula:

[0075]

[0076] Where: TS i is the time satisfaction coefficient of the unit habitat, with a value range of [0,1]. The larger the value, the longer the habitat suitability time is in the non-steady flow state; T di is the number of days that unit i is simultaneously in the habitat factor suitability interval (0-1]; T t The total number of days in the spawning stage of fish.

[0077] S5: Record the start and end dates of the unit habitat's comprehensive suitability in the suitability interval, and count the number of days that it can be continuously in the suitability interval to evaluate whether the unit can continue to be suitable for target fish spawning; Step S5 specifically includes:

[0078] (5.1) Based on step S4, record the start and end dates when the comprehensive suitability of the unit habitat is in the suitability interval (0-1]), that is, the date when the unit area is suitable for fish spawning under the non-constant flow;

[0079] (5.2) The number of consecutive days that the unit is in the suitability interval is counted. The more days, the longer the unit can adapt to fish spawning under the non-constant flow.

[0080] S6: Calculate the total dynamic suitable area of ​​fish spawning habitats, and combine the non-constant flow process Qt to establish the time series t-dynamic suitability total area HAS curve of fish habitats throughout the year, and then evaluate whether the entire river is suitable for fish spawning under the non-flow process. This curve reflects the changes in the size of the area suitable for target fish spawning in the river under the non-constant flow state set in S2, so as to evaluate the dynamic adaptability of the entire river to the spawning of target fish under this flow process.

[0081] Step S6 specifically includes:

[0082] (6.1) Use the following formula to calculate the total dynamic suitable area of ​​fish spawning grounds:

[0083]

[0084] Where: HSA is the total dynamic suitable area of ​​the spawning ground; A i is the area of ​​unit i.

[0085] (6.2) According to the non-steady flow process of S2, the time series-flow curve and the flow-dynamic suitability total area curve obtained by the above formula are recorded to establish the time series-dynamic suitability total area curve of fish habitat;

[0086] (6.3) Based on the time series-dynamic suitability total area curve, the dynamic adaptability of the entire river to the spawning of target fish under non-flow conditions is evaluated. The larger the area, the better the adaptability of the fish under this flow.

[0087] Taking the non-steady flow process of a certain working condition as an example, the non-steady flow flow-dynamic suitability total area curve of fish habitat is as follows: Figure 7 As shown in the figure, the example shows the change of the total area of ​​suitability of the river under this flow process. The target fish species begin to spawn in March and the suitability is the highest in June. The maximum area of ​​the suitable area is 0.5km 2Similarly, different flow processes have different maximum suitable areas. By comparing the maximum suitable areas corresponding to each flow process, the optimal flow process suitable for fish spawning in the river can be obtained.

[0088] By comparing the calculation results of S4-S6 under different non-constant flow rates, the dynamic suitability of fish habitats in rivers under various flow processes can be evaluated. By comparing the calculation results of S4-S6 under different flow processes, the non-constant flow process or ecological scheduling scheme suitable for fish spawning can be optimized.

[0089] What is disclosed above is only a preferred embodiment of the present invention, and cannot be used to limit the scope of rights of the present invention. Therefore, the present invention is not limited to the above optional implementation mode. Anyone can derive other various forms of products under the inspiration of the present invention. However, no matter what changes are made in its shape or structure, all technical solutions that fall within the scope defined by the claims of the present invention fall within the protection scope of the present invention.

Claims

1. A method for evaluating the dynamic suitability of fish habitats, characterized in that The following steps are involved: S1: Establish a habitat dynamic model based on the study area and target fish spawning grounds; S2: using the habitat dynamic model, dividing the river into triangular grids, taking each grid as a unit, setting the actual or designed non-constant flow process of the river, and calculating the dynamic suitability value of the habitat index of each unit under the non-constant flow process, wherein the habitat index includes water depth h, flow velocity v and water temperature T; S3: Multiply the dynamic suitability values ​​of each habitat indicator to obtain the comprehensive dynamic suitability of the unit habitat; S4: Count the number of days when the comprehensive dynamic suitability of the unit habitat meets the suitability interval (0,1) of the spawning ground habitat factors, and calculate the unit habitat time satisfaction coefficient based on the statistical number of days. The unit habitat time satisfaction coefficient is used to evaluate whether the unit is suitable for spawning of target fish for a long time; S5: Record the start and end dates of the unit habitat's comprehensive suitability in the suitability interval, and count the number of days that it can be continuously in the suitability interval to evaluate whether the unit can continue to be suitable for target fish spawning. The greater the number of continuous days, the more suitable the area is for fish spawning under non-constant flow; S6: Calculate the total dynamic suitable area of ​​fish spawning habitats, and combine it with the non-steady flow process Qt to establish the time series t-dynamic suitability total area HAS curve of fish habitats throughout the year, and then evaluate whether the entire river is suitable for fish spawning under non-flow processes.

2. The method according to claim 1, characterized in that The step S1 specifically includes: (1.1) Determine the target fish species based on the study area and select the habitat factors of the spawning grounds; conduct a survey of the target fish species, record the habitat factors of the spawning grounds of the target fish species, and collect continuous long-sequence data of the spawning grounds of the target fish species; (1.2) Conduct experimental research on target fish in the laboratory to obtain the relationship between target fish and habitat factors during the spawning stage, and obtain the suitability curve of each habitat factor during the spawning stage of target fish; (1.3) Establish a hydrodynamic-water temperature model for the study area to simulate the dynamic changes of hydrodynamic and water temperature indicators in the river sections where the target species’ habitats are located; (1.4) Based on the suitability curve of habitat factors during the fish spawning stage obtained from experimental research, and using the hydrodynamic and water temperature changes calculated by the hydrodynamic-water temperature model as the boundary, complete the modeling of the habitat dynamics model of the target fish spawning ground.

3. The method according to claim 2, characterized in that Step (1.3) specifically includes: (1.3.1) Collect data in the research area, collect underwater topography, hydrology, and water temperature data, and organize and analyze the hydrological and water temperature conditions of characteristic hydrological years; (1.3.2) Establish a hydrodynamic model for the study area and simulate the changes in the hydrodynamic indicators of the unsteady flow in the area; (1.3.3) Establish a water temperature model for the study area and simulate the changes in non-steady flow water temperature in the area.

4. The method according to claim 1, characterized in that The step S2 specifically includes: (2.1) Divide the river into grids, take each grid area as a unit, and calculate the temporal changes of various habitat indicators of each unit under the non-constant flow process in a typical year of the river; (2.2) Using the habitat dynamic model, the dynamic suitability values ​​of the unit spawning ground habitat factors water depth h, flow velocity v and water temperature T in the non-steady flow are calculated respectively, 5. The method according to claim 4, characterized in that In step S3, the following formula is used to calculate the comprehensive dynamic suitability of the unit habitat: Where: is the comprehensive dynamic suitability of habitat in unit i, t is a certain moment in the year, s, They are the dynamic suitability of flow velocity, water depth and water temperature of unit i respectively.

6. The method according to claim 1, characterized in that The step S4 specifically includes: (4.1) Taking grid cells as units, the number of days in a year when the water depth, flow velocity, and water temperature of unit i simultaneously meet the suitability interval (0, 1) of the spawning habitat factors is counted, denoted as T di ; The total number of days of the fish spawning stage is recorded as T t ; (4.2) Taking the grid unit as the unit, the unit habitat time satisfaction coefficient is calculated using the following formula: Where: TS i is the unit habitat time satisfaction coefficient, with a value range of [0,1]. The larger the value, the longer the habitat suitability time is satisfied in the non-steady flow state, and the better the dynamic adaptability of the unit area to fish spawning.

7. The method according to claim 1, characterized in that The step S5 specifically includes: (5.1) Record the start and end dates when the comprehensive suitability of the unit habitat is within the suitability interval (0-1], that is, the date when the unit area is suitable for fish spawning under the non-constant flow; (5.2) The number of consecutive days that unit i is in the suitability interval is counted. The more days, the longer the time that the non-constant flow can continue to adapt to fish spawning.

8. The method according to claim 1, characterized in that Step S6 specifically includes the following steps: (6.1) Use the following formula to calculate the total dynamic suitable area of ​​fish spawning grounds: Where: HSA is the total dynamic suitable area of ​​the spawning ground; A i is the area of ​​unit i; (6.2) According to the non-steady flow process of S2, the time series-flow curve and the flow-dynamic suitability total area curve obtained by the above formula are recorded to establish the time series-dynamic suitability total area curve of fish habitat; (6.3) Based on the time series-dynamic suitability total area curve, the dynamic adaptability of the entire river to the spawning of target fish under non-flow conditions can be evaluated. The larger the total area, the better the adaptability of the fish under this flow.

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