Target river section determination method for ecological scheduling of natural fish breeding reservoir

Abstract

The invention discloses a method for determining a dispatching target river section for ecological dispatching of a reservoir for natural breeding of fishes laying drifting eggs. The method comprises the following steps: calculating spawning site distribution of target fishes for ecological dispatching of the reservoir based on a fish early-stage resource investigation result; further analyzing fish spawning site distribution based on a breeding biology survey result; the distribution position of the fish spawning site is confirmed based on a fish acoustic detection result; further confirming the distribution position of the fish spawning site based on an environmental DNA detection result; and according to the determined specific distribution position of the scheduling target fish spawning site, determining a target river section for reservoir ecological scheduling. By means of the technical scheme, the adverse effect of reservoir dispatching operation on natural breeding of the fishes laying the drifting eggs can be relieved, and natural breeding activity of the fishes laying the drifting eggs can be promoted.

Description

Technical Field

[0001] The invention belongs to the field of ecology, and particularly relates to a method for determining a target river section for ecological dispatching of a reservoir for natural reproduction of fish with drifting eggs. Background Art

[0002] Fish that lay drifting eggs are an important ecological type among river fishes. They play a vital role in maintaining local biodiversity and improving the structure and function of ecosystems. At the same time, the realization of natural reproduction activities of fish that lay drifting eggs is closely related to specific hydrological processes. The realization of their spawning activities usually requires the stimulation of flood peak processes with certain hydrological conditions. However, the peak-cutting effect and hydrological flattening effect caused by the operation of cascade reservoirs will lead to significant changes in the conditions of natural flood pulse processes required for the natural reproduction of fish that lay drifting eggs, thereby affecting the realization of their natural reproduction activities. In order to mitigate the impact of reservoir water storage on the natural reproduction of fish that lay drifting eggs, it is necessary to use reservoir ecological regulation to create suitable spawning habitats as much as possible to ensure the natural reproduction of fish that lay drifting eggs under the dam. In the implementation of reservoir ecological regulation to promote the natural reproduction of fish that lay drifting eggs, it is very important to clarify the target river section of ecological regulation according to the specific distribution location of fish spawning grounds for scientific and effective reservoir ecological regulation. However, there is currently no method to determine the target river section for reservoir ecological regulation to promote the natural reproduction of fish that lay drifting eggs. Summary of the invention

[0003] In order to solve the problems existing in the prior art, the present invention provides a method for determining the target river section for ecological scheduling of natural reproduction reservoirs for fish laying drifting eggs. The method comprises: estimating the distribution of spawning grounds of target fish for reservoir ecological scheduling based on early fish resource survey results; further analyzing the distribution of fish spawning grounds based on reproductive biology survey results; confirming the distribution location of fish spawning grounds based on fish acoustic detection results; further confirming the distribution location of fish spawning grounds based on environmental DNA detection results; and determining the target river section for reservoir ecological scheduling according to the specific distribution location of the determined scheduling target fish spawning grounds.

[0004] In the method for determining the target river section for reservoir ecological scheduling as described above, optionally, the distribution of spawning grounds of the target fish for reservoir ecological scheduling is estimated based on early fish resource surveys, including obtaining the embryonic development time of eggs of the scheduling target fish and the flow velocity of the section upstream of the sampling point through early fish resource surveys; and estimating the distribution of spawning grounds in the river section upstream of the early fish resource sampling section based on the embryonic development time of eggs and the average flow velocity of the section upstream of the sampling point.

[0005] In the method for determining the target river section for ecological scheduling of water reservoirs as described above, optionally, the distribution of fish spawning grounds is further analyzed based on the results of reproductive biology surveys, including obtaining information such as body length, weight, developmental period, number and distribution of the target fish for scheduling through reproductive biology surveys; and further analyzing and verifying the distribution of fish spawning grounds based on the number and distribution of sexually mature individuals and the spawning ground distribution estimated from early fish resources.

[0006] In the method for determining the target river section for reservoir ecological scheduling as described above, optionally, the distribution location of fish spawning grounds is confirmed based on the results of fish acoustic surveys, including: obtaining the fish density and temporal and spatial distribution characteristics of different detection areas through fish acoustic detection; analyzing the matching between the fish clustering areas obtained from the fish acoustic survey and the spawning ground distribution locations estimated based on early resource results, so as to further confirm the distribution location of fish spawning grounds.

[0007] In the method for determining the target river section for reservoir ecological regulation as described above, optionally, the distribution location of fish spawning grounds is further confirmed based on environmental DNA (eDNA) detection, including: obtaining the species composition, relative abundance and spatial distribution characteristics of fish laying drifting eggs through eDNA detection; and further analyzing and confirming the distribution location of fish spawning grounds based on the distribution characteristics of the eDNA relative abundance with obvious peaks.

[0008] In the method for determining the target river section for reservoir ecological scheduling as described above, optionally, the target river section for reservoir ecological scheduling is determined based on the specific distribution location of the spawning grounds of the determined scheduling target fish, including: conducting on-site habitat surveys based on the above early fish resource surveys, fish reproductive biology surveys, fish hydroacoustic detection, and environmental DNA detection results, and then determining the specific spawning ground locations of the scheduling target fish; determining the target river section for reservoir ecological scheduling based on the specific spawning ground locations of the scheduling target fish.

[0009] The beneficial effects brought by this embodiment are as follows:

[0010] The distribution of spawning grounds of target fish species for reservoir ecological regulation is estimated based on the results of early fish resource surveys; the distribution of fish spawning grounds is further analyzed based on the results of reproductive biology surveys; the distribution of fish spawning grounds is confirmed based on the results of fish acoustic detection; the distribution of fish spawning grounds is further confirmed based on the results of environmental DNA detection; the target river section for reservoir ecological regulation is determined based on the specific distribution of the spawning grounds of the target fish species for regulation. Reservoir ecological regulation is carried out based on the target river section for reservoir ecological regulation, thereby alleviating the adverse effects of reservoir regulation on the natural reproduction of fish species that lay drifting eggs and promoting their natural reproduction activities. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1A flow chart of a method for determining a target river section for ecological regulation of a reservoir for natural reproduction of fish with drifting eggs provided by an embodiment of the present invention;

[0012] Figure 2 The collection location of copper fish broodstock from May to July 2022 provided by the embodiment of the present invention and its relationship with the spawning ground location estimated from the early resource survey results;

[0013] Figure 3 The collection location of broodstock of Rhinophora cylindricalis from May to July 2022 provided in the embodiment of the present invention and its relationship with the spawning ground location estimated from the early resource survey results;

[0014] Figure 4 A matching analysis between the fish clustering points obtained by acoustic detection of fish provided in the embodiment of the present invention and the spawning ground distribution locations of two important fish species (copper fish and cylindrical goby) estimated based on early resource results;

[0015] Figure 5 The corresponding relationship between the approximate distribution location of fish spawning grounds and the location of fish gathering places provided in the embodiment of the present invention;

[0016] Figure 6 The specific location of the target fish spawning ground between Mudong Town, Banan District and Shituo Town, Fuling District is provided in the embodiment of the present invention. DETAILED DESCRIPTION

[0017] To make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0018] See also Figure 1 The embodiment of the present invention provides a method for determining a target river section for ecological scheduling of a reservoir for natural reproduction of fish with drifting eggs, the method comprising the following steps:

[0019] Step 101: Calculate the approximate spawning ground distribution of target fish species for reservoir ecological regulation based on early fish resource surveys.

[0020] Specifically, the embryonic development time of fish eggs of the target fish for scheduling and the flow velocity of the upstream section of the sampling point are obtained through the early fish resource survey; the drifting distance of the fish eggs is estimated based on the collected embryonic development time of the fish eggs and the average flow velocity of the upstream section of the sampling point, and then the approximate distribution of the spawning grounds in the upstream river section of the early fish resource sampling section is determined. The calculation formula is as follows.

[0021] S=V×T / 1000

[0022] In the above formula, S is the drift distance of different types of fish eggs (km), V is the average flow velocity of the sampling point section when different types of fish eggs are collected (m / s), and T is the time (s) that the embryos of these fish eggs have experienced when different types of fish eggs are collected.

[0023] Step 102: further analyzing the distribution of fish spawning grounds based on the results of the reproductive biology survey.

[0024] Specifically, through reproductive biology surveys, we obtained information on the length, weight, development period, number and distribution of the target fish for scheduling; fish gather in groups at spawning grounds before natural reproduction, so the river sections where a large number of sexually mature individuals can be collected are the river sections where the concentrated spawning grounds of fish are specifically distributed or close to them. Based on the number and distribution of sexually mature individuals, combined with the approximate distribution of the early spawning grounds of fish resources calculated in step 101, we further analyzed and verified the distribution of fish spawning grounds.

[0025] Step 103: confirm the distribution location of fish spawning grounds based on the fish acoustic survey results.

[0026] Specifically, fish density and temporal and spatial distribution characteristics of fish in different detection areas were obtained through fish acoustic detection. The matching between the fish clustering areas obtained from the fish acoustic survey and the spawning ground distribution locations estimated based on early resource results was analyzed, and the distribution locations of fish spawning grounds were further confirmed through the relatively high-density fish clustering distribution areas.

[0027] Step 104: further confirm the distribution location of fish spawning grounds based on environmental DNA (eDNA) detection.

[0028] Specifically, eDNA detection was used to obtain the species composition, relative abundance and spatial distribution characteristics of fish species that lay drifting eggs; based on the distribution characteristics of the obvious peak in the relative abundance of eDNA, the distribution location of fish spawning grounds was further analyzed and confirmed.

[0029] Step 105: Determine the target river section for reservoir ecological regulation based on the specific distribution locations of the determined regulation target fish spawning grounds.

[0030] Specifically: Based on the above-mentioned early fish resource surveys, fish reproductive biology surveys, fish hydroacoustic detection and environmental DNA testing results, an on-site habitat survey is carried out to determine the specific spawning grounds of the target fish for scheduling; based on the specific spawning grounds of the target fish for scheduling, the target river section for the ecological scheduling of the reservoir is determined.

[0031] The distribution of spawning grounds of target fish species for reservoir ecological regulation is estimated based on the results of early fish resource surveys; the distribution of fish spawning grounds is further analyzed based on the results of reproductive biology surveys; the distribution of fish spawning grounds is confirmed based on the results of fish acoustic detection; the distribution of fish spawning grounds is further confirmed based on the results of environmental DNA detection; the target river section for reservoir ecological regulation is determined based on the specific distribution of the spawning grounds of the target fish species for regulation. Reservoir ecological regulation is carried out based on the target river section for reservoir ecological regulation, thereby alleviating the adverse effects of reservoir regulation on the natural reproduction of fish species that lay drifting eggs and promoting their natural reproduction activities.

[0032] The following takes the tail of the Three Gorges Reservoir as the implementation area to explain in detail the process of using this method to determine the target river section for ecological regulation of reservoirs that promote the natural reproduction of fish with drifting eggs:

[0033] Step 1) Estimate the approximate spawning ground distribution of target fish for reservoir ecological regulation based on early fish resource surveys.

[0034] Early fish resource surveys were conducted in Fuling section from May to July 2022 and in Mudong section from April to July 2022 to obtain the embryonic development time of the target fish eggs and the average flow velocity of the upstream section of the sampling point, and the location of the spawning grounds of the target fish (copper fish and cylindrical goby) distributed in the upstream river section of each sampling section was calculated (Table 1). At the same time, combined with the results of the early fish resource survey during the survey period, the spawning scale of the target fish (copper fish and cylindrical goby) in different spawning grounds during the survey period was obtained, as shown in Table 1 below.

[0035] Table 1 The approximate distribution and spawning scale of the spawning grounds of copperfish and cylindrical goby based on the early fish resource survey

[0036]

[0037] Step 2) Further analyze the distribution of fish spawning grounds based on the results of reproductive biology surveys.

[0038] Through the reproductive biology survey, the body length, weight, development period, number and distribution of the dispatching target fish were obtained (Table 2). Parent fish of copper fish were collected in the surveyed river sections of Yudong Street, Mudong Town and Shituo Town ( Figure 2 ), while broodstock of Rhinophora cylindrica were collected in all the investigated river sections ( Figure 3 ).

[0039] The location of the copper fish broodstock surveyed was located within the river section of the approximate spawning ground obtained based on early fish resource calculations or in the river section downstream of the spawning ground, while the location of the cylindrical goby broodstock surveyed was all located within the river section of the approximate spawning ground obtained based on early fish resource calculations.

[0040] Table 2 Survey results on reproductive biology of parent fish of the target fish species for scheduling

[0041]

[0042] Step 3) Confirm the distribution location of fish spawning grounds based on the results of fish acoustic surveys.

[0043] The fish density and temporal and spatial distribution characteristics of different detection areas were obtained through fish acoustic detection. The results showed that the three places with the highest fish density in the Mudong detection area were the waters near Zhangjia Creek, with an average density of about 2.19 ind. / 1000m 3 ; The average density of the waters on the north bank 700m downstream of the railway bridge is about 1.28ind. / 1000m 3 ; The beach waters on the south bank about 1.3 km upstream of the Mudong Town Pier have a density of about 1.80 ind. / 1000m 3 The three places with the highest fish density in the Changshou detection area are the 1.6km waters downstream of Xiaoshimen, with an average density of about 4.48ind. / 1000m 3 ; Xiaoshimen is close to the water, with an average density of about 3.34ind. / 1000m 3 ; In Shantuo Village upstream of Changshou District, the density is about 1.15ind. / 1000m 3 .

[0044] The matching of fish aggregation areas obtained from fish acoustic surveys with the spawning ground distribution locations estimated based on early resource results was analyzed ( Figure 4 ), and further confirmed the distribution of fish spawning grounds through the distribution areas of relatively high-density fish clusters. The results showed that high-density fish clusters were either directly located in the river section of the spawning ground or located near the upstream of a spawning ground, indicating that the spawning ground distribution location estimated based on early resource results is relatively accurate. Fish clusters in the spawning grounds and in the river section upstream of the spawning ground are conducive to the fish quickly entering the appropriate river section to complete the spawning process when the hydrological process is suitable. In other words, considering the fitness cost of fish spawning (minimizing the additional energy consumption during spawning), the location of the specific spawning ground of fish should be not far from the fish cluster point.

[0045] Step 4: Further confirm the distribution location of fish spawning grounds based on environmental DNA (eDNA) detection.

[0046] The species composition, relative abundance and spatial distribution characteristics of fish species that lay drifting eggs were obtained through eDNA detection. During the peak spawning period of fish (June 20-June 30), 29 species of fish species that lay drifting eggs were detected in samples collected from 52 environmental DNA monitoring sections in the Mudong Town, Banan District-Shituo Town, Fuling District. Among the 29 fish species, the species with relatively high gene sequences (frequency of OUT) include four fish species, including Cylindrospermum cylindricum, Copperfish, Mongolian bream and Chinese sand loach. In addition, the gene sequences of fish species such as Smooth-lipped Snakehead, Grass Carp, Chinese Spinularia sinensis, Silver Goby and Plowhead Loach were also relatively abundant in the samples. Among them, the relative abundance of the gene sequence of Cylindromus cylindricus in sections S5, S28, S29 and S32 was significantly higher than that in other sections, indicating that these four sections are the sections where Cylindromus cylindricus appears most in clusters; at the same time, the relative abundance of the gene sequence of Copperfish in sections S2, S4, S16, S17 and S38 was significantly higher than that in other sections, indicating that these five sections are the sections where Copperfish appears most in clusters.

[0047] Based on the distribution characteristics of the obvious peaks in the relative abundance of eDNA, further analysis was conducted to confirm the distribution of fish spawning grounds. The results of the environmental DNA survey showed that except for one section (the upstream section of Maliuzui Town) where the peak of the relative abundance of fish gene sequences appeared, all other sections were located in the river section where fish clusters were determined by fish hydroacoustic detection or adjacent to the river section ( Figure 5 ). This also shows that the river section with a significant peak in relative abundance of eDNA is the river section where fish instantaneously spawn.

[0048] Step 5: Determine the target river section for reservoir ecological regulation based on the specific distribution locations of the target fish spawning grounds.

[0049] Based on the above early fish resource surveys, fish reproductive biology surveys, fish hydroacoustic detection and environmental DNA testing, and field habitat surveys, the specific spawning sites of the dispatching target fish are determined. Based on the results of early fish resource and reproductive biology surveys, hydroacoustic detection of fish clusters in the river sections where the spawning sites are roughly distributed was conducted during the peak spawning period or after spawning. The results showed that high-density fish clusters were either directly located in the river section of the spawning site or located upstream of a spawning site, indicating that fish clusters are clearly formed during or after spawning. Furthermore, based on the results of early fish resource surveys and fish hydroacoustic surveys, the environmental DNA method was used to further confirm the specific clustering locations of drifting egg-laying fish during spawning during the peak period of fish spawning. The results showed that in the river section from Mudong Town, Banan District to Shituo Town, Fuling District, there were obvious peak values ​​of genetic material concentration in the water samples of 9 sections; through the corresponding analysis of environmental DNA, reproductive biology, early fish resource results and fish hydroacoustic detection results, it was shown that the locations of these sections were most likely the specific spawning sections of drifting egg-laying fish during spawning in the study section. Finally, based on the field habitat survey, it was found that most of the 9 sections were located at the bends of the river or the places where it suddenly narrowed, and only one section was located at the floodplain where the river entered the wide water surface from the narrow canyon, and its flow state was complex; there were large areas of gravel shoals distributed at the 9 fish clustering points or not far downstream, and these habitats are suitable habitats for many fish to spawn. In summary, the specific river sections where drifting egg-laying fish lay eggs between Mudong Town, Banan District and Shituo Town, Fuling District, are determined to be: Xiawan Village, Wangjiawan, Jiangjiawan, Shagongxi, Dashimen, Yangjiagou, Jiangnan Town, Xiawan Village and Mabanxi ( Figure 6 ).

[0050] According to the specific spawning grounds of the target fish species, the target river sections for ecological regulation of the Three Gorges Reservoir to promote the natural reproduction of fish species that lay drifting eggs at the tail of the reservoir are determined to be the Xiawan Village river section, Wangjiawan river section, Jiangjiawan river section, Shagongxi river section, Dashimen river section, Yangjiagou river section, Jiangnan Town river section, Xiawan Village river section and Mabanxi river section.

[0051] It is known from common technical knowledge that the present invention can be implemented by other embodiments that do not deviate from its spirit or essential features. Therefore, the above disclosed embodiments are only illustrative in all respects and are not exclusive. All changes within the scope of the present invention or within the scope equivalent to the present invention are included in the present invention.

Claims

1. A method for determining a target river section for ecological regulation of a reservoir for natural reproduction of fish with drifting eggs, characterized in that: The method includes: Calculate the distribution area of ​​spawning grounds of target fish species for reservoir ecological regulation based on early fish resource surveys; Confirm the distribution area of ​​spawning grounds of the target fish species based on reproductive biology surveys, fish acoustic surveys, and environmental DNA surveys; The target river section for reservoir ecological regulation is determined based on the distribution area of ​​the spawning grounds of the target fish for regulation.

2. The method for determining a target river section according to claim 1, characterized in that: The spawning ground distribution area of ​​the target fish for reservoir ecological scheduling based on the early fish resource survey includes: obtaining the embryonic development time of the eggs of the scheduling target fish and the flow velocity of the section upstream of the sampling point through the early fish resource survey; based on the embryonic development time of the eggs and the average flow velocity of the section upstream of the sampling point, the spawning ground distribution area in the river section upstream of the early fish resource sampling section is estimated.

3. The method for determining a target river section according to claim 2, characterized in that: Confirming the distribution area of ​​spawning grounds of the target fish for scheduling based on reproductive biology surveys includes: obtaining the body length, weight, developmental period, number and distribution information of the target fish for scheduling through reproductive biology surveys; determining the distribution area of ​​spawning grounds of the target fish for scheduling based on the number and distribution of sexually mature individuals, combined with the distribution area of ​​spawning grounds of the target fish for reservoir ecological scheduling estimated based on early fish resource surveys.

4. The method for determining a target river section according to claim 3, characterized in that: Confirming the distribution area of ​​spawning grounds of the target fish for scheduling based on fish acoustic surveys includes: obtaining the fish density and temporal and spatial distribution characteristics of different detection areas through fish acoustic detection; matching the fish clustering areas obtained from the fish acoustic surveys with the spawning ground distribution of the target fish for reservoir ecological scheduling estimated based on early fish resource surveys, to further confirm the distribution area of ​​spawning grounds of the target fish for scheduling.

5. The method for determining a target river section according to claim 4, characterized in that: The spawning ground distribution areas of the target fish for scheduling are confirmed based on environmental DNA surveys, including: obtaining the species composition, relative abundance and spatial distribution characteristics of fish species that lay drifting eggs through environmental DNA testing; based on the distribution characteristics of obvious peaks in environmental DNA relative abundance, combined with the spawning ground distribution areas of the target fish for reservoir ecological scheduling estimated based on early fish resource surveys, the spawning ground distribution areas of the target fish for scheduling are further confirmed.

6. The method for determining a target river section according to claim 5, characterized in that: According to the distribution area of ​​the spawning grounds of the target fish spawning grounds for scheduling, the target river section for the ecological scheduling of the reservoir is determined, including: determining the river section containing the section in the distribution area of ​​the spawning grounds of the target fish spawning grounds for scheduling as the target river section for the ecological scheduling of the reservoir.

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