A method for accurately locating the wintering grounds of schizothorax in frozen rivers on the Qinghai-Tibet Plateau

Abstract

A method for accurately locating fish wintering grounds in a continuously frozen river on the Qinghai-Tibet Plateau comprises the following steps: determining a study area as a continuously frozen river section; determining a continuously frozen period; locating a water body position: searching for a live water body position in the continuously frozen river section, and determining the found water body position as a potential wintering ground; and determining the potential wintering ground as the final wintering ground if the following conditions are met in the potential wintering ground: (1) determining that typical fish species are present in the potential wintering ground; (2) determining that the potential wintering ground has a wintering period and wintering ground loyalty; (3) determining that there are hot springs, and that the hot springs have a heating effect on the potential wintering ground; (4) determining that the potential wintering ground has a deep water area formed by concave bank erosion; and (5) determining that the potential wintering ground has food sufficient for fish wintering. The present invention can accurately locate wintering grounds in continuously frozen rivers, which is conducive to better understanding the habitat and migration patterns of fish, and protecting the wintering grounds of fish and the fish species in the Qinghai-Tibet Plateau.

Description

Technical Field

[0001] The present invention relates to the field of fish habitat positioning, and in particular to a method for accurately positioning fish wintering grounds in frozen rivers on the Qinghai-Tibet Plateau. Background Art

[0002] Fish wintering grounds refer to waters where fish live in clusters during the winter. In winter, fish face factors that are not conducive to survival, such as low water temperature and low dissolved oxygen, and fish need to enter the wintering grounds to survive. Wintering grounds can provide better cover or shelter conditions and provide sufficient food resources. In rivers and streams in high-altitude and high-latitude areas, wintering grounds are the limiting factor for the size of fish populations, and the mortality rate of fish during the wintering period is the determining factor of fish productivity. The Qinghai-Tibet Plateau has the third coldest place in the world with ice and snow content second only to the Arctic and Antarctic, and is known as the Third Pole. The source parts of many major Asian rivers, called source rivers, are distributed in the hinterland of the Qinghai-Tibet Plateau. In the high-altitude and cold Qinghai-Tibet Plateau, source rivers have the characteristics of small flow, slow gradient of the river channel, and little water in winter. Under the influence of extreme low temperatures in winter, source rivers generally freeze at the bottom, and all the river water from the river surface to the river bottom is frozen. Figure 1 As shown, even the frozen river section has no water and fish cannot survive.

[0003] Previous studies have shown that there are two ways for schizothorax to overwinter: (1) In rivers with continuous bottom freezing on the Qinghai-Tibet Plateau that are connected to rivers and lakes, fish often migrate downstream to overwinter in deep lakes where the rivers flow into. For example, Qinghai Lake is the overwintering ground for naked carp of Qinghai Lake; (2) schizothorax migrate to deep rivers downstream where continuous bottom freezing does not occur. For example, schizothorax overwinter in rock caves, a phenomenon that occurs in deep rivers without continuous bottom freezing. Because the Dangqu River section in the southern source of the Yangtze River experiences continuous bottom freezing in winter and has no connected lakes, the overwintering method of schizothorax is different from the two overwintering methods studied by previous researchers. Dangqu is located in the high altitude area in the heart of the Qinghai-Tibet Plateau, in Zaduo County, Yushu Prefecture, Qinghai Province, with a total length of 352 km. The average altitude of the river is over 4,600 meters, and continuous bottom freezing occurs in winter. In terms of fish composition, a total of five fish species were found in the southern source of the Yangtze River, two schizothorax fish and four plateau loaches. Among them, the small-headed naked schizothorax, the most highly distributed cyprinid fish, is also the most evolved schizothorax species following the uplift of the Qinghai-Tibet Plateau. It is endemic to my country, possessing exceptionally high scientific, ecological, and economic value, and a key species in the Yangtze River's source region. How do fish survive the winter when the Yangtze River's southern source region experiences continuous bottom freezing, and where do they find their wintering grounds? These are the primary questions to be answered in fish habitat research. Do fish migrate downstream to deeper reaches like the Tongtian River, where continuous bottom freezing doesn't occur, or does another overwintering mechanism exist? The small-headed naked schizothorax has adapted to the ecological environment of the Yangtze River's source region on the Qinghai-Tibet Plateau, exhibiting a strong geographically isolated distribution. It is rarely found in the lower Jinsha River and is absent from the lower-elevation Tongtian River section in Qumalai County and the Jinsha River below. Based on its geographical distribution, it is determined that this fish will not migrate long distances down the river (migration distance exceeds 600km) to overwinter in the downstream sections of the Jinsha River and other rivers where continuous bottom freezing does not occur. There is only one possible hypothesis left: there may be overwintering grounds in the southern source of the Yangtze River where continuous bottom freezing occurs in winter.

[0004] Currently, studies on the location of fish wintering grounds are often conducted in rivers and lakes where continuous bottom freezing does not occur, using targeted winter netting methods. These studies often rely on deepwater overwintering. For example, fish wintering ground research was conducted in the Shaanxi section of the Yellow River from 2014 to 2015. In 2017, the location of fish wintering grounds in the Songhua River and their ecological water requirements were studied. In 2018, the impact of the Yangqu Hydropower Station on fish wintering grounds in the upper Yellow River was assessed. These studies were conducted within flowing river sections, excluding those with continuous bottom freezing. Their formation mechanisms did not address the presence of living water bodies. Other studies focus on the impact of other environmental factors, such as water temperature, on fish survival and growth in wintering grounds, rather than on the location of wintering grounds. In cold regions of Canada, striped bass also face extremely cold winters, and the presence of wintering grounds is crucial for the fish to complete its life cycle. As of 2018, Canadian researchers remain eager to locate and characterize the wintering grounds of striped bass to support their conservation efforts. Especially due to the sharp decline in fish populations in winter, it has become very difficult to carry out relevant research on the location of overwintering grounds and the mechanism of overwintering ground formation.

[0005] There are relatively few patents on the location and formation mechanism of fish overwintering grounds. The reason is that in rivers where continuous bottom freezing does not occur, deep water areas often become overwintering grounds. A certain water depth provides overwintering space and shelter for fish, which is the fundamental reason for the formation of overwintering grounds. The mechanism is relatively simple. Other patents focus on ecological flow research methods. For example, "A method for calculating the ecological base flow of rivers during the ice-covered period (CN107292118B)" emphasizes the size of the flow. This method is applicable to frozen rivers where continuous bottom freezing does not occur. For rivers with continuous bottom freezing, the flow rate, flow rate, etc. related to ecological flow are not decisive factors. This method is not suitable for studying the formation mechanism of rivers with continuous bottom freezing.

[0006] The significance of accurately locating fish wintering grounds on the Qinghai-Tibet Plateau is as follows: (1) It can better understand the migration and wintering behavior of fish, and understand the location and characteristics of fish wintering grounds, which will help to formulate corresponding protection measures, protect fish habitats and breeding populations, and provide a scientific basis for fish protection. (2) While accurately locating and protecting fish wintering grounds on the Qinghai-Tibet Plateau, it also protects other aquatic organisms in the wintering grounds and wintering migratory birds that feed on fish, maintains biodiversity, and maintains the ecological balance of the region. It is a fundamental response to the protection of the Yangtze River. The two wintering methods revealed by previous researchers are not applicable to the southern source of the Yangtze River where continuous bottom freezing occurs. It is urgent to invent a new method for locating fish wintering grounds in the southern source of the Yangtze River where continuous bottom freezing occurs. Summary of the Invention

[0007] The purpose of the present invention is to provide a method for accurately locating the wintering grounds of fish in rivers with continuously frozen bottoms on the Qinghai-Tibet Plateau. Accurately locating the wintering grounds in rivers with continuously frozen bottoms is conducive to better understanding the habitats and migration patterns of fish, protecting the wintering grounds of fish on the Qinghai-Tibet Plateau and the fish belonging to them, and providing scientific support for the protection of the Qinghai-Tibet Plateau.

[0008] To achieve the above object, the technical solution adopted by the present invention is:

[0009] A method for accurately locating fish wintering grounds in a frozen river on the Qinghai-Tibet Plateau comprises the following steps:

[0010] Step 1: Determine the study area as the continuous bottom frozen river section, and set up monitoring sections in the continuous bottom frozen river section as shown in the attached figure;

[0011] Step 2: Determine the continuous bottom freezing period: Use a fully automatic water temperature and water level recorder to monitor the water temperature. The start time of the continuous bottom freezing is when the water temperature reaches 0°C and then begins to drop continuously. The end time of the continuous bottom freezing is when the temperature gradually rises back to zero degrees and the water temperature continues to rise until it is no longer below 0 degrees in the following year. This is used to determine the continuous bottom freezing period of the study river section.

[0012] Step 3: Locate the water body: After determining the bottom-freezing period, search for active water bodies within the bottom-freezing river section and identify the water bodies found as potential wintering grounds.

[0013] Step 4: If the following conditions are met in the potential wintering ground, the potential wintering ground is determined as the final wintering ground:

[0014] (1) Determine the presence of typical fish species in potential wintering grounds;

[0015] (2) determine potential wintering grounds with wintering period and wintering ground fidelity;

[0016] (3) Determine that a hot spring is found 1-2 km upstream along the potential meltwater section, and that the hot spring has a heating effect on the potential wintering grounds;

[0017] (4) Identify potential wintering grounds with deep water areas formed by concave bank erosion;

[0018] (5) Determine whether potential wintering grounds have sufficient food for fish to survive the winter.

[0019] Furthermore, in step three, the location of the active water body in the frozen river section is to distinguish whether there is water under the ice based on the color of the ice surface. The frozen river section is visually white, and the river section with water under the ice and snow is blue.

[0020] Furthermore, in step 4, the potential wintering grounds are determined to have wintering period and wintering ground fidelity, including:

[0021] The bioadhesive bonding-ultrasonic telemetry technology was used to study the time when typical adult fish leave and return to the wintering grounds. The typical fish overwintering period was determined based on the time period from the fish returning to the wintering grounds in autumn to leaving the wintering grounds the following year. If fish overwinter in the same wintering ground for two consecutive years, it indicates that the fish are loyal to the wintering ground.

[0022] Furthermore, the bio-glue bonding-ultrasonic telemetry technology is specifically as follows: the captured adult fish are implanted into the abdominal cavity with a V9 series ultrasonic marker, the water temperature during marking is 1.0-3.5°C, and the marker is implanted into the abdominal cavity using bio-glue bonding instead of surgical sutures. After the bio-glue is dried, the marked fish is placed back into another fish pond to gradually recover its strength to swim normally, and then released back into the wintering grounds.

[0023] Furthermore, the basis for finding the heat source 1-2 km upstream along the potential meltwater section in step 4 is: the wintering site is the meltwater section, and the other river sections are in a frozen state. The heat source is determined by the real-time water temperature process changes along the way; it is determined that the heat source has a heating effect on the potential wintering site, specifically: three key locations are set at the heat source, the heat source confluence and the wintering site, and a fully automatic water temperature recorder is used to monitor the annual hourly water temperature process. The measurement range of the thermometer used for the heat source is 0-125℃, and the measurement range of the thermometer used for the heat source confluence and the wintering site is -20-40℃, with a measurement accuracy of 0.1℃; linear fitting is performed on the water temperature at the confluence during the wintering period and the water temperature in the wintering site to determine the heating effect of the heat source on the wintering site.

[0024] Furthermore, in step 4, it is determined whether the potential wintering grounds have deep water areas formed by concave bank erosion. Specifically, the water depth in the shallow water area is measured by wading through the river and using a ruler, and the deep water area is measured using a micro-underway acoustic Doppler current profiler. The river channel morphology characteristics are detected using remote sensing images or drone aerial photography. Combined with the water depth characteristics and river channel morphology characteristics, an analysis is carried out to determine whether there are deep water areas formed by concave bank erosion.

[0025] Furthermore, step four determines whether the potential overwintering grounds have food that can meet the needs of fish overwintering, which specifically includes: collecting typical fish during the overwintering period, analyzing the intestinal fullness, feeding rate and diet composition of the fish, so as to determine whether the potential overwintering grounds have food that can meet the needs of fish overwintering.

[0026] Furthermore, the method also includes step five, judging whether the fish can safely survive the wintering period through the survival status of the fish during the entire wintering period, thereby judging the quality of the wintering ground.

[0027] The beneficial effects of the present invention are:

[0028] (1) Accurately located fish wintering grounds in rivers on the Qinghai-Tibet Plateau, achieving a breakthrough from zero to one such wintering ground;

[0029] (2) The monitoring period for the wintering site is when the river bottom is frozen rather than when the ice melts in the early or late winter, which maximizes the time for locating the wintering site;

[0030] (3) The invention uses biological glue to bond the marking opening on the abdomen of adult fish, avoiding the secondary damage to the fish caused by surgical sutures, making the survival rate of marked adult fish greater than 98%, which is suitable for the research method of fish habitat fidelity. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic diagram of the frozen river sections on the Qinghai-Tibet Plateau;

[0032] Figure 2 This is a schematic diagram of the fish wintering grounds in the frozen rivers on the Qinghai-Tibet Plateau;

[0033] Figure 3 This is a schematic diagram of the deep water area formed by erosion of the concave banks in the wintering grounds of fish on the Qinghai-Tibet Plateau.

[0034] The reference numerals in the figure are described as follows: 1—curved river channel, 2—water flow, 3—river bend angle, 4—water flow direction, 5—deep water area formed by concave bank erosion. DETAILED DESCRIPTION

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0036] The Yangtze River's source rivers, the Tuotuo, Dangqu, and Chumar rivers, are all located in the heart of the Qinghai-Tibet Plateau. Winters are extremely cold, and suitable wintering grounds are essential for fish survival. A key characteristic of these source rivers is their low flow and shallow waters, often resulting in bottom freezing in temperatures as low as -30 to -40°C during winter. Six species of fish are also found in the Yangtze River's source areas. In winter, fish face unfavorable conditions such as low water temperatures and low dissolved oxygen levels, forcing them to enter wintering grounds. Suitable wintering grounds for fish in rivers and streams must minimize energy expenditure and provide maximum protection. Large adult fish in streams, lacking sufficient rock cover for protection, often overwinter in deep pools, using deep water as a refuge. Avoiding adverse winter habitat conditions such as low water temperatures and dissolved oxygen, and utilizing depth or surface ice for protection from predators, are two key factors for river fish wintering. Many fish do not completely stop moving in winter and continue to feed throughout the wintering period, even when the temperature drops below 5°C. Therefore, food is the third important condition for the formation of fish wintering grounds.

[0037] Based on the winter hydrological conditions and fish populations of the Yangtze River source region, the present invention aims to identify sections of rivers with continuously frozen bottoms, determine the duration of continuous freezing in these sections, and locate live water bodies within these sections during the continuous freezing period. Within these live water bodies, the presence of overwintering fish is observed, and the fish population and key species are identified. Once the fish population is determined, the water body is identified as a wintering ground. Fish loyalty to wintering grounds is demonstrated through bioadhesive bonding and ultrasonic telemetry technology. Heat sources are traced, and the heating effect of heat sources on wintering grounds is revealed by fitting the heat source with the water temperature during the wintering process. Water depth distribution and river channel type are analyzed to reveal the mechanism of concave bank erosion formed in deepwater areas. Dietary analysis is used to reveal the food satisfaction mechanism during the wintering period. Finally, the mechanism of fish wintering ground formation within the continuously frozen bottom rivers of the Yangtze River source region is determined based on water temperature, water depth, and food availability. Finally, the quality of the wintering grounds is assessed based on the survival of the fish after the wintering period.

[0038] The following describes it in detail through specific embodiments.

[0039] Example 1

[0040] Precise positioning of fish wintering grounds in frozen rivers in the upper reaches of the Yangtze River

[0041] (1) Determine the research area of the frozen river section

[0042] The study area was determined to be the upper reaches of Dangqu River.

[0043] (2) Determine the continuous bottom freezing period

[0044] Based on the river bottom temperature process obtained from in-situ monitoring, it was analyzed that the continuous bottom freezing period is from early December to mid-May.

[0045] (3) Locating the water body

[0046] An observation route was set up from downstream to upstream. Live water bodies were found in the frozen river sections during the continuous bottom-freezing period and identified as potential wintering grounds. Figure 2 As shown, there is water between the ice structures at both ends, and the colors are obviously different, the ice is white and the water is cyan.

[0047] (4) Determine the composition of fish

[0048] The fish population in the river section with water was determined. Juveniles and adults of Triplophysa microphthalma, Triplophysa spinulosa, and Triplophysa swineri were found in this section, as well as juveniles of Gymnosoma microcephala, with Gymnosoma microcephala being the key species.

[0049] (5) Determine the wintering period and wintering site loyalty

[0050] Determine the typical overwintering period for fish. Results from bioadhesive bonding and ultrasonic telemetry indicate that the overwintering period for fish in the upper reaches of the river runs from November 2nd to May 19th. Tagged fish consistently returned to the overwintering grounds and overwintered there over the three-year observation period.

[0051] (6) Determine the location of the heat source

[0052] The heat source is determined by the real-time water temperature change along the process. The water temperature change function along the process is simulated. The model of water temperature T (℃) and the distance d (m) from the heat source is T = 23-0.01d, R 2 =0.90. The water temperature in the wintering grounds decreases linearly from the upstream hot spring to the downstream deep water area, but the lowest water temperature in the wintering grounds remains above zero degrees.

[0053] (7) Determine the heating effect of heat sources on the wintering grounds

[0054] Compared with the frozen state of the bottom, the water in the wintering site always remains in the liquid state under the action of hot springs. The linear fitting result of the water temperature in the wintering site (Y) and the water temperature at the confluence during the wintering period (X) is: Y = 0.84X-7.7, R 2 =0.52, indicating that the water temperature of the wintering site changes with the water temperature at the confluence, thereby confirming the heating effect of the hot spring on the wintering site.

[0055] (8) Study the formation mechanism of deep water areas

[0056] The deep water area is more than 0.8m deep and 150m long. The wintering ground river channel has a 90° concave bank, which forms a horizontal circulation during the flood season, eroding the inner river channel of the concave bank and forming a deep pool. The concave bank erosion is the reason for the formation of the deep water area in the wintering ground. Figure 3As shown: 1 is the bend in the river channel at the wintering ground, 2 is the water flow, which flows upward and downward, 3 is the angle of the river bend, 4 is the direction of the water flow, and 5 is the deep water area formed by concave bank erosion.

[0057] (9) Study on the mechanism of food satisfaction during winter

[0058] During the continuous bottom freezing period, the fish feeding rate reached 70%, the intestinal fullness index reached level 2, and the intestinal contents were mainly diatoms and zooplankton. In addition, the spiny plateau loach fed a large amount of benthic animals.

[0059] The fish survival rate during the wintering period reached 98%, with some losses coming from predation by wintering migratory birds. The extremely high survival rate of fish after wintering proves that the wintering ground is of extremely high quality.

[0060] Example 2

[0061] Precise positioning of fish wintering grounds in frozen rivers in the middle reaches of the southern source of the Yangtze River

[0062] (1) Determine the research area of the frozen river section

[0063] The study area was determined to be the middle reaches of Dangqu River.

[0064] (2) Determine the continuous bottom freezing period

[0065] According to the river bottom temperature process obtained from in-situ monitoring, it is analyzed that the continuous bottom freezing period starts from mid-December.

[0066] Ten days to the end of April.

[0067] (3) Locating the water body

[0068] An observation route was set up from downstream to upstream, and living water bodies were found in the frozen river sections during the continuous bottom freezing period.

[0069] (4) Determine the composition of fish

[0070] The fish species composition in the river section with water was determined. Juveniles and adults of Triplophys sphenodon, Triplophys sternii, Triplophys slendertail, and Triplophys slendertail were found in this section.

[0071] (5) Determine the wintering period and wintering site loyalty

[0072] Determine the typical overwintering period for fish. Monitoring indicates that the overwintering period for fish in the middle reaches of the river is from November 10th to May 15th. During the three-year observation period, marked fish consistently returned to their overwintering grounds and overwintered there.

[0073] (6) Determine the location of the heat source

[0074] The heat source is determined by the real-time water temperature change along the route. The water temperature change function along the route is simulated to determine the heating effect of the heat source on the wintering ground. The model of water temperature T (℃) and distance d (m) from the heat source is T = 30-0.01d, R 2 =0.97. The water temperature in the wintering grounds showed a linear decreasing trend from the upstream hot spring to the downstream deep water area, but the lowest water temperature in the wintering grounds remained above zero degrees.

[0075] (7) Determine the heating effect of heat sources on the wintering grounds

[0076] Compared with the frozen state of the bottom, the water in the wintering site always remains in the liquid state under the action of hot springs. The linear fitting result of the water temperature in the wintering site (Y) and the water temperature at the confluence during the wintering period (X) is Y = 0.76X-6.4, R 2 =0.66, indicating that the water temperature of the wintering site changes with the water temperature at the confluence, thereby confirming the heating effect of the hot spring on the wintering site.

[0077] (8) Study the formation mechanism of deep water areas

[0078] The deep water zone is over 0.9 meters deep and 140 meters long. The wintering grounds have an 80-degree concave bank, which creates a horizontal circulation during flood season, eroding the inner bank and forming a deep pool. This concave bank erosion is the cause of the deep water zone in the wintering grounds.

[0079] (9) Study on the mechanism of food satisfaction during winter

[0080] During the continuous bottom freezing period, the fish feeding rate reached 80%, the intestinal fullness index reached level 2, and the intestinal contents were mainly diatoms and zooplankton. In addition, the spiny plateau loach fed a large amount of benthic animals.

[0081] After the wintering period, the fish survival rate reached 99%, and part of the loss was caused by the predation of wintering migratory birds. The extremely high survival rate of fish after wintering proves that the wintering ground is of extremely high quality.

[0082] Example 3

[0083] Precise positioning of fish wintering grounds in frozen rivers in the lower reaches of the Yangtze River

[0084] (1) Determine the research area of the frozen river section

[0085] The study area was determined to be the lower reaches of Dangqu River.

[0086] (2) Determine the continuous bottom freezing period

[0087] Based on the river bottom temperature process obtained from in-situ monitoring, it was analyzed that the continuous bottom freezing period is from mid-to-late December to mid-April.

[0088] (3) Locating the water body

[0089] An observation route was set up from downstream to upstream, and living water bodies were found in the frozen river sections during the continuous bottom freezing period.

[0090] (4) Determine the composition of fish

[0091] The fish population in the river section with water was determined. Juveniles and adults of Triplophysa microphthalma, Triplophysa spinulosa, Triplophysa swineri, and Triplophysa swineri were found in this section, with Triplophysa microcephala being the key species.

[0092] (5) Determine the wintering period and wintering site loyalty

[0093] Determine the typical overwintering period for fish. Monitoring indicates that the overwintering period for fish in the downstream river reaches from November 20 to May 10. During the three-year observation period, marked fish consistently returned to the overwintering grounds and overwintered there.

[0094] (6) Determine the location of the heat source

[0095] The heat source is determined by the real-time water temperature change along the route. The water temperature change function along the route is simulated to determine the heating effect of the heat source on the wintering site. The model of water temperature T (℃) and distance d (m) from the heat source are T = 40-0.009d, R 2 =0.95. The water temperature in the wintering grounds decreases linearly from the upstream hot spring to the downstream deep water area, but the lowest water temperature in the wintering grounds remains above zero degrees.

[0096] (7) Determine the heating effect of heat sources on the wintering grounds

[0097] Compared with the frozen state of the bottom, the water in the wintering site always remains in the liquid state under the action of hot springs. The linear fitting result of the water temperature in the wintering site (Y) and the water temperature at the confluence during the wintering period (X) is Y = 0.70X-9.2, R 2 =0.73, indicating that the water temperature of the wintering ground changes with the water temperature at the confluence, thereby confirming the heating effect of the hot spring on the wintering ground.

[0098] (8) Study the formation mechanism of deep water areas

[0099] The deep water zone is over 1 meter deep and 200 meters long. The wintering grounds have a 70-degree concave bank. During flood season, lateral circulation forms, eroding the inner bank and forming deep pools. This concave bank erosion is the cause of the deep water zone in the wintering grounds.

[0100] (9) Study on the mechanism of food satisfaction during winter

[0101] During the continuous bottom freezing period, the fish feeding rate reached 76%, the intestinal fullness index reached level 2-3, and the intestinal contents were mainly diatoms and zooplankton. In addition, the spiny plateau loach fed on a large number of benthic animals, and the adult small-headed naked fish fed on both fish and benthic animals.

[0102] After the wintering period, the fish survival rate reached 96%, part of the loss was caused by the predation of wintering migratory birds. The extremely high survival rate of fish after wintering proves that the wintering ground is of extremely high quality.

[0103] The present invention uses a precise positioning method to discover fish wintering grounds in the frozen rivers of the southern source of the Yangtze River. The number of overwintering fish reached 90,000, including 32,000 adult fish of the cyprinid fish, the world's highest-altitude cyprinid fish, which wintered in the southern source wintering grounds. This demonstrates the important role of the southern source wintering grounds in the wintering habitat of fish in the Yangtze River source. Key fish species showed extremely high loyalty to the wintering grounds, overwintering there during the three years of observation, indicating the importance of the discovered wintering grounds to specific groups of fish. The inventors of this application found that the breeding population of cyprinid fish returned to the wintering grounds from late October to mid-November and left in mid-to-late May. The survival rate of fish after wintering was extremely high, proving that the discovered wintering grounds were of extremely high quality. The present invention achieves the precise positioning of high-quality fish wintering grounds in the source of the Yangtze River. This method is also applicable to the precise positioning of fish wintering grounds in other frozen rivers of the Qinghai-Tibet Plateau.

[0104] The invention's precise positioning of wintering grounds during the period of continuous bottom-freezing in river sections is crucial. This period is optimal for identifying wintering grounds within these sections, as meltwater in other sections of the river would otherwise interfere with the identification of wintering grounds. To determine the fish's wintering period, a bio-adhesive-ultrasonic telemetry technique was used to ultrasonically tag adult fish, resulting in a survival rate exceeding 95%, ensuring the survival of the experimental fish and the accuracy of the experiment.

[0105] The influx of hot springs is a unique mechanism for the formation of wintering grounds for fish on the Qinghai-Tibet Plateau. The formation of wintering grounds in frozen rivers on the Qinghai-Tibet Plateau requires three necessary conditions: (1) the influx of hot springs; (2) the formation of deep water areas by erosion of concave banks; and (3) the shift in the diet of key adult fish from their summer herbivorous diet to a carnivorous one. The precise location of wintering grounds for fish on frozen rivers on the Qinghai-Tibet Plateau was first discovered and revealed by the inventors of this application. Therefore, the method for precisely locating wintering grounds for fish on frozen rivers on the Qinghai-Tibet Plateau proposed in this invention is scientific, innovative, and original, and is a pioneering work in both the field of fish habitat research and the patent field. This invention can also provide a reference for research and inventions in the same field at home and abroad.

[0106] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for accurately locating fish wintering grounds in frozen rivers on the Qinghai-Tibet Plateau, characterized by: The steps include: Step 1: Determine the study area as the frozen river section with continuous bottom, and set up monitoring sections in the frozen river section with continuous bottom; Step 2: Determine the continuous bottom freezing period: Use a fully automatic water temperature and water level recorder to monitor the water temperature. The start time of the continuous bottom freezing is when the water temperature reaches 0°C and begins to drop continuously. The end time of the continuous bottom freezing is when the temperature gradually rises back to 0°C and the water temperature continues to rise until it no longer drops below 0°C in the following year. This is used to determine the continuous bottom freezing period of the study river section. Step 3: Locate the water body: After determining the bottom-freezing period, search for active water bodies within the bottom-freezing river section and identify the water bodies found as potential wintering grounds. Step 4: If the following conditions are met in the potential wintering ground, the potential wintering ground is determined as the final wintering ground: (1) Determine the presence of typical fish species in potential wintering grounds; (2) determine potential wintering grounds with wintering period and wintering ground fidelity; (3) Determine that a hot spring is found 1-2 km upstream along the potential meltwater section, and that the hot spring has a heating effect on the potential wintering grounds; (4) Identify potential wintering grounds with deep water areas formed by concave bank erosion; (5) Determine whether potential wintering grounds have sufficient food for fish to survive the winter.

2. The method for accurately locating fish wintering grounds in frozen rivers on the Qinghai-Tibet Plateau according to claim 1, characterized in that: In step three, the location of active water bodies in the frozen river section is to distinguish whether there is water under the ice based on the color of the ice surface. The frozen river section is visually white, and the river section with water under the ice and snow is blue.

3. The method for accurately locating fish wintering grounds in frozen rivers on the Qinghai-Tibet Plateau according to claim 1, characterized in that: In step 4, potential wintering grounds are determined to have wintering period and wintering ground fidelity, including: The bioadhesive bonding-ultrasonic telemetry technology was used to study the time when typical adult fish leave and return to the wintering grounds. The typical fish overwintering period was determined based on the time period from the fish returning to the wintering grounds in autumn to leaving the wintering grounds the following year. If fish overwinter in the same wintering ground for two consecutive years, it indicates that the fish are loyal to the wintering ground.

4. The method for accurately locating fish wintering grounds in frozen rivers on the Qinghai-Tibet Plateau according to claim 3, characterized in that: The bio-glue bonding-ultrasonic telemetry technology is specifically as follows: the V9 series ultrasonic markers are used to implant the markers into the abdominal cavity of the captured adult fish. The water temperature during marking is 1.0-3.5°C. The markers are implanted into the abdominal cavity using bio-glue bonding instead of surgical sutures. After the bio-glue is air-dried, the marked fish are placed back into another fish pond to gradually recover their strength to swim normally, and then released back into the wintering grounds.

5. The method for accurately locating fish wintering grounds in frozen rivers on the Qinghai-Tibet Plateau as claimed in claim 1, characterized in that: In step 4, the basis for finding the heat source hot spring 1-2 km upstream along the potential meltwater section is: the wintering site is the meltwater section, and the other river sections are in a continuous bottom frozen state. The heat source hot spring is determined by the real-time water temperature process changes along the way; it is determined that the heat source hot spring has a heating effect on the potential wintering site, specifically: three key locations are set at the heat source, the heat source confluence and the wintering site, and a fully automatic water temperature and water level recorder is used to monitor the annual hourly water temperature process with a measurement accuracy of 0.1°C; a linear fit is performed on the confluence water temperature and the wintering site water temperature during the wintering period to determine the heating effect of the heat source hot spring on the wintering site.

6. The method for accurately locating fish wintering grounds in frozen rivers on the Qinghai-Tibet Plateau as claimed in claim 1, characterized in that: In step 4, determine whether the potential wintering grounds have deep water areas formed by concave bank erosion. Specifically, the water depth in the shallow water area is measured by wading through the river and using a ruler, and the deep water area is measured using a micro-underway acoustic Doppler current profiler. The river channel morphology characteristics are detected using remote sensing images or drone aerial photography. Combined with the water depth characteristics and river channel morphology characteristics, analysis is carried out to determine whether there are deep water areas formed by concave bank erosion.

7. The method for accurately locating fish wintering grounds in frozen rivers on the Qinghai-Tibet Plateau according to claim 1, characterized in that: Step 4 determines whether the potential overwintering grounds have sufficient food for fish to overwinter, specifically including: collecting typical fish during the overwintering period, analyzing the intestinal filling degree, feeding rate and diet composition of the fish, so as to determine whether the potential overwintering grounds have sufficient food for fish to overwinter.

8. The method for accurately locating fish wintering grounds in frozen rivers on the Qinghai-Tibet Plateau as claimed in claim 1, characterized in that: It also includes step five, judging whether the fish can safely survive the wintering period through the survival status of the fish throughout the wintering period, so as to judge the quality of the wintering ground.

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