Method for evaluating dynamic suitability of fish habitat

Abstract

The application discloses a kind of fish habitat dynamic suitability evaluation method, consider the dynamic change characteristics of annual non-constant water depth, flow rate, water temperature and other habitat habitat factors of river, according to the dynamic response curve of habitat factor change of fish habitat suitability, the change process of each region suitability and weighted available area in year is calculated in river, on this basis, the number of days suitable for each region in fish spawning stage in river is counted, the time satisfaction coefficient and suitable time duration days located in the interval of suitability are calculated, and the annual change curve of dynamic suitability total area is described.Through the above calculation method, the adaptability of fish spawning stage to river in the whole year can be more reasonably evaluated, so as to more scientifically guide the operation of ecological regulation.

Description

Technical Field

[0001] This invention relates to the field of ecohydraulics technology, specifically to a method for evaluating the dynamic suitability of fish habitats. Background Technology

[0002] Current habitat suitability assessment methods all study the impact of river physical, chemical, and biological characteristics on indicator species habitats using a constant-condition design, thereby obtaining the range and quality of suitable habitats for fish at different life stages. However, in reality, rivers have non-constant flow throughout the year, and fish selection of spawning grounds and other habitats is a dynamic assessment. Studies have shown that fish spawning requires continuous and appropriate stimulation of water depth, flow velocity, and water temperature. However, current habitat models do not consider the effects of non-constant river flow throughout the year and do 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 temperature of rivers throughout the year, especially during the spawning period. Further improvements are needed to refine the scientific basis of ecological regulation.

[0003] In summary, this invention provides a method for evaluating the dynamic suitability of fish habitats, aiming to solve the above-mentioned problems. Summary of the Invention

[0004] The purpose of this invention is to provide a method for evaluating the dynamic suitability of fish habitats, to more reasonably evaluate the adaptability of fish during the spawning stage to the non-steady flow of rivers throughout the year, and thus to more scientifically guide the operation of ecological regulation.

[0005] To achieve the above-mentioned objectives, the technical solution adopted in this invention is a method for evaluating the dynamic suitability of fish habitats, comprising the following steps:

[0006] S1: Establish a habitat dynamic model based on the study area and the spawning grounds of the target fish;

[0007] S2: Using the aforementioned habitat dynamic model, the river is divided into triangular grids. Each grid is a unit. An actual or designed non-constant flow process of the river is set, and the dynamic suitability value of the habitat factors of each unit under the non-constant flow process is calculated. The habitat factors include water depth h, flow velocity v, and water temperature T.

[0008] S3: Multiply the dynamic fitness values ​​of each habitat factor to obtain the overall dynamic fitness of the unit habitat;

[0009] S4: The number of days that the comprehensive dynamic suitability of the habitat of the statistical unit simultaneously meets the suitability range (0,1) of the spawning ground habitat factors. The unit habitat time satisfaction coefficient is calculated based on the statistical number of days. The unit habitat time satisfaction coefficient is used to evaluate whether the unit can be suitable for the target fish to spawn for a long time.

[0010] S5: Record the start and end dates of the overall dynamic suitability of the habitat of the unit within the suitability range, and count the number of days that can be continuously within the suitability range. This is used to evaluate whether the unit can be continuously suitable for the spawning of target fish. The longer the number of consecutive days, the more suitable the unit is for fish spawning under non-constant flow conditions.

[0011] S6: Calculate the dynamic suitable total area of ​​fish spawning ground habitat, and combine it with the non-constant flow process Qt to establish the time series t-dynamic suitability total area HAS curve of fish habitat throughout the year, so as to evaluate whether the entire river is suitable for fish spawning under the non-constant flow process.

[0012] Furthermore, step S1 specifically includes:

[0013] (1.1) Based on the study area, identify the target fish species 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-term data of the spawning grounds of the target fish species.

[0014] (1.2) Conduct experimental research on the target fish in the laboratory to obtain the relationship between the target fish and habitat factors during the spawning stage, and obtain the suitability curves of each habitat factor for the target fish during the spawning stage;

[0015] (1.3) Establish a hydrodynamic-temperature model for the study area to simulate the dynamic changes of hydrodynamic and temperature indicators in the river section where the target species' habitat is located;

[0016] (1.4) Based on the habitat factor suitability curves obtained from the experimental study, and using the hydrodynamic and water temperature change processes calculated by the hydrodynamic-water temperature model as the boundary, the habitat dynamic model of the target fish spawning ground is completed.

[0017] Furthermore, step (1.3) specifically includes:

[0018] (1.3.1) Data collection in the study area: collect underwater topography, hydrology, and water temperature data, and organize and analyze the hydrological and water temperature conditions of characteristic hydrological years;

[0019] (1.3.2) Establish a hydrodynamic model for the study area to simulate the changes in unsteady hydrodynamic parameters of the area;

[0020] (1.3.3) Establish a water temperature model for the study area to simulate the non-steady flow water temperature changes in the area.

[0021] Furthermore, step S2 specifically includes:

[0022] (2.1) Divide the river into grids, and use the grids as units. Based on the non-constant flow process of the river in a typical year, calculate the changes of each habitat factor over time in each unit under the non-constant flow process.

[0023] (2.2) Using the aforementioned habitat dynamic model, the dynamic suitability values ​​of water depth h, flow velocity v, and water temperature T for the unit spawning ground habitat factors in unsteady flow were calculated, respectively. , , .

[0024] Furthermore, in step S3, the comprehensive dynamic suitability of the unit habitat is calculated using the following formula:

[0025]

[0026] In the formula: Let t represent the overall dynamic fitness of habitat for unit i, where t is a point in time within the year. , , These are the dynamic suitability of flow velocity, dynamic suitability of water depth, and dynamic suitability of water temperature for unit i, respectively.

[0027] Furthermore, step S4 specifically includes:

[0028] (4.1) Using a grid as the unit, count the number of days in a year where the water depth, flow velocity, and water temperature of unit i simultaneously meet the suitability range (0,1] of the spawning ground habitat factors, denoted as . The total number of days in the fish spawning stage is recorded as follows: ;

[0029] (4.2) Using the grid as the unit, the time satisfaction coefficient of the unit habitat is calculated using the following formula:

[0030]

[0031] In the formula: The value is the habitat time satisfaction coefficient of the unit, with a value range of [0,1]. The larger the value, the longer the habitat suitability is satisfied in the non-steady flow state, and the better the dynamic adaptability of the unit to fish spawning.

[0032] Furthermore, step S5 specifically includes:

[0033] (5.1) Record the start and end dates of the overall dynamic suitability of the habitat of the recording unit being in the suitability range (0-1], which are the dates when fish in the unit are suitable for spawning under the non-constant flow.

[0034] (5.2) The number of consecutive days that statistical unit i is in the suitability interval. The more days, the longer the fish can adapt to spawning under the non-constant flow.

[0035] Furthermore, step S6 specifically includes the following steps:

[0036] (6.1) The dynamic suitable total area of ​​fish spawning grounds is calculated using the following formula:

[0037]

[0038] In the formula: The dynamic suitable total area of ​​the spawning grounds; Let i be the area of ​​cell i;

[0039] (6.2) Based on the non-constant flow process of S2, record the time series-flow curve and the flow-dynamic fitness total area curve obtained by the above formula, and establish the time series-dynamic fitness total area curve of fish habitat;

[0040] (6.3) Based on the time series-dynamic fitness total area curve, the dynamic adaptability of the entire river to the spawning of target fish under non-constant flow process can be evaluated. Different flow processes have different maximum suitable areas. By comparing the maximum suitable areas corresponding to each flow process, the optimal flow process for fish spawning in the river can be obtained.

[0041] This invention offers the following advantages: It considers the dynamic changes in river habitat factors such as non-constant water depth, flow velocity, and water temperature throughout the year. Based on the dynamic response curve of fish habitat suitability to changes in habitat factors, it calculates the annual changes in suitability and weighted usable area for each region within the river. Furthermore, it statistically analyzes the number of suitable days for each region during the fish spawning stage, calculates the time satisfaction coefficient and the number of consecutive days within the suitability interval, and plots the annual change curve of the total dynamic suitability area. This calculation method allows for a more reasonable evaluation of the river's adaptability during the fish spawning stage throughout the year, thus providing more scientific guidance for ecological management. Attached Figure Description

[0042] Figure 1 This is a flowchart of a method for evaluating the dynamic suitability of fish habitats according to the present invention;

[0043] Figure 2 A grid partitioning diagram of the river region;

[0044] Figure 3 The habitat factor variation curves (h~t, v~t, T~t) for unit i.

[0045] Figure 4The habitat suitability curve for a certain fish species ( ~V、 ~H、 ~T);

[0046] Figure 5 The habitat factor dynamic suitability value curve for unit i ( ~t、 ~t、 ~t);

[0047] Figure 6 The comprehensive dynamic fitness value curve of unit i ( ~t);

[0048] Figure 7 This is a schematic diagram of the dynamic curve of total area of ​​fish over time and with dynamic fitness. Detailed Implementation

[0049] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings.

[0050] This invention provides a method for evaluating the dynamic suitability of fish habitats, specifically as follows: Figure 1 As shown, considering the dynamic changes in river habitat factors such as non-constant water depth, flow velocity, and water temperature throughout the year, the annual changes in the suitability and weighted usable area of ​​each region in the river are calculated based on the dynamic response curve of fish habitat suitability to changes in habitat factors. Furthermore, the number of suitable days for each region in the river during the fish spawning stage is statistically analyzed, the time satisfaction coefficient and the number of consecutive days within the suitability interval are calculated, and the annual change curve of the total dynamic suitability area is plotted. This includes the following steps:

[0051] S1: Establish a habitat dynamic model based on the study area and the spawning grounds of the target fish;

[0052] (1.1) Based on the ecosystem of the study area, identify the target fish species and select the habitat factors of the spawning grounds; conduct a survey of the target fish species, record the habitat factors such as time, location, area, water depth, flow velocity, and water temperature of the target fish spawning grounds, and collect continuous long-term data of the target fish spawning grounds.

[0053] Using a section of the Yangtze River basin as the study area, and based on recent regional fish surveys, a rare fish species was selected as a representative of drifting-egg-laying fish. This fish has specific requirements for its spawning grounds, and its eggs require drifting to hatch. Habitat factors such as water depth, current velocity, and water temperature were recorded at the surveyed spawning grounds.

[0054] (1.2) Conduct experimental research on the target fish in the laboratory to obtain the relationship between the target fish and habitat factors such as water depth, flow velocity, and water temperature during the spawning stage, and obtain the suitability curve of the target fish and habitat factors during the spawning stage.

[0055] Numerous studies have been conducted on the habitat suitability curves for this fish. This study utilizes existing suitability curves for current velocity, water depth, and water temperature. Figure 3 As shown.

[0056] (1.3) Establish a hydrodynamic-temperature model for the study area to simulate the dynamic changes in hydrodynamic and temperature indicators of the river section where the target species' habitat is located; step (1.3) specifically includes:

[0057] (1.3.1) Data collection in the study area: collect underwater topography, hydrology, and water temperature data, and organize and analyze the hydrological and water temperature conditions of characteristic hydrological years;

[0058] (1.3.2) Establish a hydrodynamic model for the study area to simulate the changes in unsteady hydrodynamic parameters of the area;

[0059] (1.3.3) Establish a water temperature model for the study area to simulate the non-steady flow water temperature changes in the area;

[0060] The rivers in the study area are divided into grids, such as... Figure 2 As shown in the figure. A two-dimensional hydrodynamic and water temperature model is used, with the annual inflow process of the regional river as the boundary, to simulate the changes in water depth, velocity, and water stability in unsteady flow. Taking a certain unit i as an example, the simulation results of velocity, water depth, and water temperature are as follows. Figure 4 As shown.

[0061] (1.4) Establish a habitat dynamic model of the target fish spawning ground: Based on the habitat factor suitability curve of fish spawning stage obtained by experimental research, and with the hydrodynamic and water temperature change process calculated by the hydrodynamic-water temperature model as the boundary, complete the modeling of the habitat dynamic model of the target fish spawning ground.

[0062] S2: Using the aforementioned habitat dynamic model, the river is divided into triangular grids. Each grid is considered a unit. An actual or designed non-constant flow process is defined for the river. The dynamic suitability values ​​of habitat factors such as water depth h, flow velocity v, and water temperature T are calculated for each unit under the non-constant flow process. These values ​​are used to subsequently calculate the comprehensive dynamic suitability of the unit's habitat. Step S2 specifically includes:

[0063] (2.1) Divide the river into grids, with each grid area as a unit. Based on the non-constant flow process of the river in a typical year, calculate the changes of each habitat factor (water depth h, flow velocity v, water temperature T) over time in each unit under the non-constant flow process.

[0064] (2.2) Using the habitat dynamic 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 unsteady flow was recorded. , , .

[0065] Using the habitat dynamic model established in step (1.4), the dynamic fitness of habitat factors in the spawning grounds of river units was calculated. Taking unit i as an example, the calculated dynamic fitness curve of habitat factors is shown below. Figure 5 As shown.

[0066] S3: Multiply the dynamic fitness values ​​of each habitat factor to obtain the overall dynamic fitness of the unit habitat; specifically, using a grid as the unit, the overall dynamic fitness of the unit is calculated using the following formula:

[0067]

[0068] In the formula: Let t represent the overall dynamic fitness of habitat for unit i, where t is a point in time within the year. , , These are the dynamic suitability of flow velocity, dynamic suitability of water depth, and dynamic suitability of water temperature for unit i, respectively.

[0069] The above formula is then used to calculate the overall dynamic fitness of the river unit. Taking unit i as an example, the calculated overall dynamic fitness curve is shown below. Figure 6 As shown.

[0070] S4: Calculate the number of days that the comprehensive dynamic suitability of the habitat of a statistical unit simultaneously meets the suitability range (0,1) of the spawning ground habitat factors. Based on the statistically counted number of days, calculate the unit's habitat time satisfaction coefficient to evaluate whether the unit can be suitable for the target fish to spawn for an extended period. Step S4 specifically includes:

[0071] (4.1) Using a grid as the unit, count the number of days in a year when the water depth, flow velocity, water temperature, and other factors in unit i are simultaneously within the suitable range of spawning ground habitat factors, denoted as . The total number of days in the fish spawning stage is recorded as follows: ;

[0072] (4.2) Using the grid as the unit, the time satisfaction coefficient of the unit habitat is calculated using the following formula:

[0073]

[0074] In the formula: The unit habitat time satisfaction coefficient has a value range of [0,1]. The larger the value, the longer the habitat suitability time is satisfied in the non-steady flow state. The number of days that unit i is simultaneously located within the habitat factor suitability range (0-1); This represents the total number of days during the fish spawning stage.

[0075] S5: Record the start and end dates of the overall dynamic suitability of the habitat of the unit within the suitability range, and count the number of days that the habitat can remain within the suitability range continuously, to evaluate whether the unit can sustainably provide suitable spawning conditions for the target fish; Step S5 specifically includes:

[0076] (5.1) Based on step S4, record the start and end dates when the comprehensive dynamic suitability of the unit habitat is in the suitability range (0-1), which are the dates when the unit is suitable for fish to spawn under the non-constant flow.

[0077] (5.2) The number of consecutive days that the statistical unit is in the suitability range. The more days, the longer the fish can adapt to spawning under the non-constant flow.

[0078] S6: Calculate the dynamic suitable total area of ​​fish spawning ground habitat. Combined with the non-constant flow process Qt, establish the annual time series t-dynamic suitability total area HAS curve of fish habitat to evaluate whether the entire river is suitable for fish spawning under the non-constant flow process. This curve reflects the change in the area of ​​the river suitable for target fish spawning under the non-constant flow state set in S2, thus evaluating the dynamic adaptability of the entire river to target fish spawning under this flow process.

[0079] Step S6 specifically includes:

[0080] (6.1) The dynamic suitable total area of ​​fish spawning grounds is calculated using the following formula:

[0081]

[0082] In the formula: The dynamic suitable total area of ​​the spawning grounds; Let be the area of ​​cell i.

[0083] (6.2) Based on the non-constant flow process of S2, record the time series-flow curve and the flow-dynamic fitness total area curve obtained by the above formula, and establish the time series-dynamic fitness total area curve of fish habitat;

[0084] (6.3) Based on the time series-dynamic fitness total area curve, evaluate the dynamic adaptability of the entire river to the spawning of target fish under non-constant flow process. The larger the area, the better the adaptability of the fish under the flow.

[0085] Taking a non-steady flow process under a certain operating condition as an example, the non-steady flow-dynamic fitness total area curve of fish habitat is as follows: Figure 7 As shown in the example diagram, the total area of ​​suitability for the river changes under this flow process. The target fish species begin to spawn in March, with the suitability peaking in June, when the maximum suitable area reaches 0.5 km². 2 Similarly, different flow processes have different maximum suitable areas. By comparing the maximum suitable areas corresponding to each flow process, the optimal flow process for fish spawning in the river can be obtained.

[0086] By comparing the S4-S6 calculation results for different non-constant flow rates, the dynamic suitability of fish habitats in rivers under various flow processes can be evaluated. Furthermore, by comparing the S4-S6 calculation results for different flow processes, suitable non-constant flow processes or ecological scheduling schemes for fish spawning can be selected.

[0087] The above-disclosed embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the invention. Therefore, the present invention is not limited to the above-described optional embodiments. Anyone can derive other products in various forms under the guidance of the present invention. However, regardless of any changes made in their shape or structure, any technical solution that falls within the scope of the claims of the present invention shall be protected within the scope of the present invention.

Claims

1. A method for evaluating the dynamic suitability of fish habitats, characterized in that The method comprises the following steps: S1: establishing a habitat dynamic model based on a study area and a target fish spawning ground; S2: adopting the habitat dynamic model, dividing a river into triangular grids, taking each grid as a unit, setting an actual or designed unsteady flow process of the river, and calculating a dynamic suitability value of each unit under the unsteady flow process, wherein the habitat factors include water depth h, flow velocity v, and water temperature T; S3: multiplying the dynamic suitability values of each habitat factor to obtain a unit habitat comprehensive dynamic suitability; S4: counting the number of days when the unit habitat comprehensive dynamic suitability meets the spawning ground habitat factor suitability interval (0, 1], and calculating a unit habitat time satisfaction coefficient according to the counted number of days, wherein the unit habitat time satisfaction coefficient is used to evaluate whether the unit can be suitable for the target fish spawning for a long time; S5: recording the start and end dates of the unit habitat comprehensive dynamic suitability in the suitability interval, and counting the number of days that can continuously be in the suitability interval, which is used to evaluate whether the unit can be suitable for the target fish spawning for a long time, and the greater the number of continuous days, the more suitable the unit is for the fish spawning under the unsteady flow; S6: calculating a total dynamic suitability area of the fish spawning ground habitat, combining the unsteady flow process Q-t, and establishing a time series t-dynamic suitability total area HAS curve of the fish habitat throughout the year, so as to evaluate whether the entire river is suitable for the fish spawning under the unsteady flow process.

2. The method of claim 1, wherein, The step S1 specifically comprises: (1.1) determining a target fish based on a study area, selecting habitat factors of a spawning ground, investigating the target fish, recording habitat factors of the target fish spawning ground habitat, and collecting long sequence data of the target fish spawning ground habitat; (1.2) conducting experimental research on the target fish in a laboratory to obtain the relationship between the target fish in the spawning stage and the habitat factors, and obtaining the suitability curve of each habitat factor of the target fish in the spawning stage; (1.3) establishing a water dynamics-temperature model of the study area to simulate the dynamic changes of water dynamics and temperature indexes of a river section where the target species habitat is located; (1.4) taking the suitability curve of the habitat factors of the fish in the spawning stage obtained by the experimental research as a basis, and taking the water dynamics and temperature change process calculated by the water dynamics-temperature model as a boundary, the habitat dynamic model of the target fish spawning ground is completed.

3. The method of claim 2, wherein, The step (1.3) specifically comprises: (1.3.1) collecting underwater topography, hydrology, and water temperature data, and analyzing the characteristics of the hydrology and water temperature of a characteristic hydrology year; (1.3.2) establishing a water dynamics model of the study area to simulate the changes of unsteady flow water dynamics indexes of the region; (1.3.3) establishing a water temperature model of the study area to simulate the changes of unsteady flow water temperature of the region.

4. The method of claim 1, wherein, The step S2 specifically comprises: (2.1) dividing the river into grids, taking the grid as a unit, and calculating the changes of each habitat factor with time under the unsteady flow process of a typical year of the river; (2.2) The habitat dynamic model is used to calculate the dynamic suitability values of the habitat factors of water depth h, flow velocity v and water temperature T of the oviposition site in the non-constant flow, respectively, as follows , , .

5. The method of claim 4, wherein, In the step S3, the unit habitat comprehensive dynamic suitability is calculated by the following formula: ； wherein: is the overall habitat suitability of unit i at time t, t is a time within a year, , , are the flow velocity suitability, water depth suitability, and water temperature suitability of unit i, respectively.

6. The method of claim 1, wherein, The step S4 specifically comprises: (4.1) Statistics the number of days in which the water depth, flow velocity, water temperature of the unit i in the year meet the habitat factor suitability interval (0, 1] of the spawning ground, denoted as ; and the total number of days in the fish spawning stage is denoted as ; (4.2) Calculate the unit habitat time satisfaction coefficient by using the following formula: ； In the formula: is the unit habitat time meeting coefficient, the value range is [0, 1], and the larger the value is, the longer the habitat suitability time meeting in the unsteady flow state is, and the better the dynamic adaptability of the unit to fish spawning is.

7. The method of claim 1, wherein, The step S5 specifically comprises: (5.1) Record the start and end dates of the unit habitat comprehensive dynamic suitability in the suitability interval (0-1], which is the date of the unit suitable for fish spawning under the non-constant flow; (5.2) Count the number of consecutive days that the unit i is in the suitability interval, and the more the number of days, the longer the time that can continuously adapt to fish spawning under the non-constant flow.

8. The method of claim 1, wherein, Step S6 specifically comprises the following steps: (6.1) Calculate the total area of the dynamic suitability of the fish spawning ground by using the following formula: ； wherein: is the total area of the dynamic suitability of the egg laying site; is the area of unit i, is the habitat integrated dynamic suitability of unit i; (6.2) According to the non-constant flow process of S2, record the time sequence-flow curve and the flow-dynamic suitability total area curve obtained by using the above formula, and establish the time sequence-dynamic suitability total area curve of the fish habitat; (6.3) According to the time sequence-dynamic suitability total area curve, the dynamic adaptability of the whole river to the target fish spawning under the non-constant flow process can be evaluated, and different maximum suitable areas exist under different flow processes. By comparing the maximum suitable areas corresponding to each flow process, the optimal flow process suitable for fish spawning in the river is obtained.

Images