Plateau river schizothorax spawning site position and habitat characteristic investigation method

Abstract

The invention provides a plateau river schizothorax spawning site position and habitat characteristic investigation method. The method comprises the steps that 1, the breeding time of schizothorax in a target river section is determined; 2, preliminarily determining the spawning water area of the schizothorax in the target river section; and step 3, in-situ investigation of a spawning site. And 4, carrying out habitat investigation on the spawning site. And step 5, analyzing to obtain the spawning site conditions of the schizothorax. According to the method, precise positioning of the spawning site of the schizothorax is efficiently and rapidly obtained, and habitat characteristics of the spawning site are mastered.

Description

Technical Field

[0001] The invention belongs to the technical field of schizothorax spawning ground positioning, and in particular relates to a method for investigating the location and habitat characteristics of schizothorax spawning grounds in plateau rivers. Background Art

[0002] Fish spawning ground investigation is an important part of fish ecology and resource protection research. It is of great significance for mastering basic theoretical research such as the characteristics of fish reproductive behavior, the response of fish reproduction to habitat conditions, and carrying out applications such as natural reproduction protection of fish and spawning ground restoration.

[0003] Schizothorax is a group of carp fish that are endemic to the plateaus of Asia. They live in rivers with fast currents and low water temperatures on the Qinghai-Tibet Plateau. There are more than 80 species of schizothorax in China. The Qinghai-Tibet Plateau is the area where schizothorax are most concentrated. Schizothorax mostly lay sinking eggs, which is different from the characteristics of fish that lay drifting eggs. For a long time, due to the difficulty of conducting field surveys in plateau rivers, research on the spawning behavior, spawning site location and spawning environmental conditions of schizothorax has been almost blank. Among the existing fish spawning site positioning methods, the fish spawning site positioning methods with patent announcement numbers CN108932377B, CN115413608B and CN113111956B all focus on fish that lay drifting eggs, and are not suitable for schizothorax that lay sinking eggs. Patent number CN117356485A only introduces the method of locating the spawning grounds of the Yangtze River source small-headed naked fish, and the field empirical investigation data is limited, and it has not been well extended to the investigation of spawning grounds of schizothorax fish in other rivers.

[0004] Prior art 1 A method for accurately locating the spawning grounds of schizothoracine fish, patent number CN117356485A. Public steps 1. Determine the research area; step 2. Determine the sexual maturity period according to the size of the egg diameter and the stage of gonad development, and then determine whether spawning behavior has occurred according to whether the eggs are emptied and whether the anal fin of the parent fish is broken, and determine the spawning time accordingly; step 3. According to the research area determined in step 1, identify the river section of the spawning ground of the schizothoracine fish determined in step 2 during the spawning period of the schizothoracine fish; step 4. Carry out accurate locating of the spawning ground in the river section of the spawning ground determined in step 3; determine the specific time of spawning within the spawning period obtained in step 2, and after determining the specific spawning time, accurately locate the spawning ground of the schizothoracine fish.

[0005] Disadvantages of the prior art 1 (1) This invention only solves the problem of locating the spawning grounds of the genus Schizothoracis, which is widely distributed and has relatively low spawning environment requirements. Its applicability to other schizothoracic fish is unclear, especially for species that are difficult to obtain sufficient samples through fish resource surveys. Steps 1 and 2 of this invention are difficult to implement and cannot be extended to the spawning ground surveys of other schizothoracic fish.

[0006] (2) The invention is costly. Steps 1 and 2 require a large amount of preliminary work on fish resources and fish biology dissection, which is time-consuming and difficult to quickly determine the location of the spawning grounds of schizothorax in a certain area.

[0007] (3) The invention is unable to obtain systematic data on the environmental conditions required for spawning of schizothorax fish, and is therefore unable to support the specific needs of schizothorax fish spawning ground protection and restoration work. Summary of the invention

[0008] The purpose of the present invention is to solve the defects of the above-mentioned prior art and provide a method for investigating the location and habitat characteristics of spawning grounds of schizothorax in plateau rivers.

[0009] The present invention is based on the first large amount of empirical data from field investigations in China, and obtains the precise location and habitat characteristic parameters of the spawning grounds of schizothorax. On this basis, according to the response relationship between biological behavior and environmental characteristics in the principles of fish ecology, the precise positioning of the spawning grounds in the target waters is obtained, and the key habitat elements of the spawning grounds and their suitable parameter ranges are clarified. Different from the past methods of inferring the spawning grounds of schizothorax only through a small amount of field investigation data and a large amount of qualitative description literature, the present invention can accurately obtain the location of the spawning grounds of schizothorax and collect early resource samples such as eggs and fry, and clarify the key habitat elements of the spawning grounds of schizothorax and their suitable parameter ranges based on a large amount of field investigation data. The present invention can accurately locate the spawning grounds of schizothorax, fill the gap in investigation technology, and provide scientific support for the investigation and protection of schizothorax habitats.

[0010] The present invention adopts the following technical solution: The survey method for the location and habitat characteristics of spawning sites of schizothorax in plateau rivers includes the following steps: Step 1. Determine the breeding period of schizothorax in the target waters through literature research and mature broodstock surveys.

[0011] Step 2. Based on the description in existing literature, infer the distribution of river sections where the spawning grounds of snapper fish are located.

[0012] Step 3. Based on the breeding period determined in the literature and the inferred river section location of the spawning ground, conduct field investigations to confirm the location of the spawning ground by obtaining samples of schizothorax fish eggs and fry.

[0013] Step 4. In the determined spawning grounds, simultaneously measure habitat elements such as water temperature, flow rate, water depth, bottom type, turbidity, dissolved oxygen, water temperature and pH value of the spawning grounds.

[0014] Step 5. Based on the developmental stages of fish eggs and fry obtained from field surveys, as well as species identified by morphological and molecular methods, determine the type and time of spawning, analyze the habitat conditions of the spawning grounds, and determine the key elements of the spawning ground habitat and the appropriate conditions of each parameter.

[0015] Furthermore, step 1 specifically includes: consulting literature, determining the main reproductive period of schizothorax based on the reproductive biology of schizothorax in the target area (the annual variation of the sex body index and gonad development in reproductive biology) or the otolith solar ring of larvae and juveniles, using the monthly variation graph of the gonad maturation coefficient, and the appearance period of stage IV, V and VI gonads in the biological research results, and further combining the spawning date inferred from the otolith solar ring research of larvae and juveniles to finally determine the main spawning period of schizothorax in the target area.

[0016] Furthermore, step 2 specifically includes: clarifying the main distribution range of schizothorax fish resources based on the temporal and spatial distribution characteristics described in the literature, and on this basis, preliminarily determining the main river sections for spawning schizothorax fish based on the qualitative description of the habitat characteristics of the spawning grounds and the distribution positions of broodstock with gonad development stages V or VI collected in the mature broodstock survey.

[0017] And the spatiotemporal distribution characteristics of schizothorax resources refer to the spatial distribution of adult and fry of schizothorax; the habitat characteristics of the spawning ground refer to the river bottom quality, water depth and flow velocity characteristics of the target river section.

[0018] Furthermore, step 3 specifically includes: conducting verification of the main spawning period and spawning river sections of schizothorax according to the target areas of steps 1 and 2, using targeted sampling tools based on the characteristics of schizothorax in laying sinking eggs, selecting representative waters for field investigations, performing morphological identification and molecular confirmation on the collected eggs and fry, clarifying the spawning species of schizothorax, and determining the spawning time based on early developmental characteristics.

[0019] Furthermore, step 4 includes, based on the fish spawning grounds determined by the field investigation in step 3, simultaneously conducting a detailed habitat investigation to obtain detailed data on environmental factors of the spawning grounds of schizothorax fish, clarifying the habitat conditions for spawning of schizothorax fish, and analyzing key habitat elements and appropriate parameter ranges.

[0020] The detailed data of spawning environment factors include: bottom conditions, water flow velocity, water depth, water temperature, dissolved oxygen, transparency, pH value and longitude and latitude.

[0021] Furthermore, step 5 includes analyzing and summarizing the location and time of spawning grounds and spawning habitat requirements of schizothorax fish in the target river section.

[0022] Beneficial effects of the present invention: (1) The present invention has conducted preliminary literature research and preparation work, and has initially mastered the breeding time and spawning habitat characteristics of schizothorax in the target waters, without the need for a large number of on-site investigations of fish resources and fish biology. The most important thing is to combine the characteristics of spawning by schizothorax to invent a targeted method for collecting fish eggs. After practical verification, the present invention is scientific and efficient, and has achieved the first precise positioning and habitat investigation of schizothorax spawning grounds in a large river section in China.

[0023] (2) The present invention has a clear path and is applicable to the investigation of spawning sites of schizothorax fish that lay sinking eggs in plateau rivers, and is easy to promote.

[0024] (3) The habitat characteristics of the spawning grounds of schizothorax obtained by the present invention can provide more accurate guidance for the investigation of spawning grounds of schizothorax in other regions, and can also effectively support the protection and restoration of spawning grounds of schizothorax. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a diagram of the on-site sampling process of the spawning ground of the present invention.

[0026] Figure 2 These are fertilized eggs of schizothorax obtained from a hand-scoop net.

[0027] Figure 3 These are microscopic photos of the collected fish eggs.

[0028] Figure 4 It is a flow chart of the steps of the present invention.

[0029] Schizothorax: It is a general term for fish of the schizothorax subfamily of the Cyprinidae family of the order Cypriniformes. It is only distributed in the Qinghai-Tibet Plateau and its surrounding areas, and there are more than 80 species in my country.

[0030] Fish spawning ground: A body of water that can provide suitable environmental conditions for fish reproduction. It is a key place for fish to reproduce. Different fish have their own specific spawning ground environmental conditions. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention is described clearly and completely below. 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 creative work are within the scope of protection of the present invention.

[0032] Example According to the method of the present invention, a main stream and tributary of a large plateau river in the middle reaches are selected to carry out investigation and assessment of the spawning grounds of schizothorax. The specific investigation area is the main stream of the lower middle reaches of a large plateau river, as well as the downstream of the main tributaries and the confluence section.

[0033] like Figure 4 As shown, the method for investigating the location and habitat characteristics of spawning grounds of plateau river schizothorax of the present invention comprises: Step 1. Determine the main spawning period of schizothorax in the target river section.

[0034] According to literature, the main schizothorax species distributed in the middle reaches of a certain plateau river are Lhasa schizothorax, giant beard schizothorax, heterodontoschizothorax, bibarbelly leaf beard schizothorax, Lhasa naked schizothorax and sharp naked carp. Liu Jieya's (2016) survey showed that the breeding period of giant beard schizothorax is from March to April. Lai Bolin's (2024) analysis of the otolith sun rings of heterodontoschizothorax larvae and juveniles collected showed that the hatching time in 2022 was from March 11 to May 2, and based on the accumulated temperature, it was estimated that its breeding time was from February 8 to April 23.

[0035] Combining the data on fish biology and otolith solar rings of larval and juvenile fish, it was determined that the breeding period of schizothorax fish in this area is from February to May.

[0036] Step 2. Determine the spawning waters of schizothorax in the target river section.

[0037] The survey data of fish larvae and juveniles in the middle and lower reaches of a large plateau river show that the larvae and juveniles of these schizothorax have been collected in this river section. Combined with the results of fish biology surveys, mature parent fish with gonadal development to stage IV and V of giant schizothorax, heterodontoschizothorax, Lazaro schizothorax, and bibarbelly leaf barbel have been collected in this river section, indicating that the spawning grounds of these fish are distributed in this river section. According to relevant literature, schizothorax generally spawn in river sections with gravel and sand as the bottom. The spawning grounds require certain water flow conditions. After the eggs are laid, they fall into the cracks of gravel to hatch. Some schizothorax even dig shallow pits in the gravel area of ​​the river beach to lay eggs and hatch in them. Among them, the sharp naked carp, Lhasa schizothorax, heterodontia schizothorax, and giant beard schizothorax mostly spawn in long pebble beaches with relatively coarse gravel, steady water flow, and shallow water depth; the Lhasa naked schizothorax and double-bearded leaf beard spawn in waters with relatively gentle water flow and fine gravel, and their spawning grounds are mostly river backwaters or tributary confluences. According to the literature and the situation of fry, egg-flowing or sperm-flowing broodstock (gonad development to stage V) investigated by the application team in the early stage, the spawning grounds of schizothorax in the target area may be distributed in the main and tributary rivers, and it is speculated that they are mainly distributed in the downstream of large tributaries, estuaries, and the wide valley waters of the adjacent main stream where they merge.

[0038] Step 3. In situ survey of spawning grounds.

[0039] Based on the main spawning periods and spawning river sections of schizothorax in the target area determined in steps 1 and 2, and in view of the characteristics of schizothorax in laying sinking eggs, targeted sampling tools are used to select representative waters for field investigations, and the collected eggs and fry are morphologically identified and molecularly confirmed. The species of spawning schizothorax are identified, the spawning time is estimated based on the early developmental characteristics, and the location of the spawning grounds is confirmed.

[0040] Based on the comprehensive analysis of literature, the survey method of spawning grounds of schizothorax in the middle and lower reaches of a large plateau river was determined, which is as follows: (1) Survey time and river section The survey will be carried out from March to April 2024, and the surveyed river sections include the main stream of the middle and lower reaches of the target river, as well as the downstream and confluence sections of the main tributaries.

[0041] (2) Survey methods ① Field sample collection method In combination with the spawning characteristics of schizothorax and the characteristics of the spawning ground habitat, fish eggs are mainly collected by kicking the hand net. The specific process is as follows: place the hand net (mesh size 0.5-0.8mm) close to the riverbed, kick the bottom sediment upstream of the hand net with your feet, collect the stirred suspended matter into the net, and then select the collected fish eggs and fry. Figure 1 shown.

[0042] ②Species identification and sample preservation The collected eggs are counted, observed for developmental period, and cultured one by one. When the morphological characteristics are obvious, species identification is carried out in combination with relevant literature, and relevant records are kept. The fry are fixed in 7% formalin solution, picked out after 15 minutes, counted one by one, and stored in 5% formalin. The fry collected each time are placed in labels and stored separately for species identification in the laboratory.

[0043] The number of eggs and fry of each type of fish in each sample and the developmental period of each fish were recorded separately. Part of the samples were taken for each sample and preserved in anhydrous ethanol. For samples with doubtful species identification, they were directly preserved in anhydrous ethanol to facilitate molecular genetic identification later. Referring to the description of the morphological characteristics of eggs and fry of related species in the literature, the species were identified under a stereomicroscope based on the measurable traits, countable traits and pigment characteristics. Figure 2-Figure 3 shown.

[0044] For samples with doubtful morphological identification, molecular genetic identification is performed. Genomic DNA is extracted from the collected molecular samples (eggs or fry fixed with anhydrous ethanol), followed by PCR amplification and sequencing. The obtained mtDNA Cytb or COI gene sequences are compared with known standard sequences (the corresponding standard sequences are obtained by sequencing accurately identified morphological samples) to confirm the species.

[0045] Step 4. Conduct habitat surveys of spawning grounds.

[0046] Based on the fish spawning grounds determined by the field survey in step 3, a detailed habitat survey is carried out simultaneously to obtain detailed data on environmental factors of the spawning grounds of schizothorax fish, clarify the habitat conditions for spawning of schizothorax fish, and analyze key habitat elements and appropriate parameter ranges.

[0047] While collecting eggs and fry of schizothorax fish, a survey of habitat conditions in the spawning grounds was also conducted simultaneously. The specific survey contents are as follows.

[0048] Habitat characteristics: Portable devices such as current meters, laser rangefinders and depth sounders were used to simultaneously collect river width (m), water depth (m), flow velocity (m / s) and bottom sediment type as habitat spatial factors. The bottom sediment types were divided into sand (<4 mm), fine gravel (4-8 mm), coarse gravel (8-16 mm), small pebbles (16-32 mm), large pebbles (32-64 mm), small pebbles (64-128 mm), large pebbles (128-256 mm) and boulders (>256 mm).

[0049] Water body physical and chemical factors: During the survey, water temperature (℃), dissolved oxygen (mg / L), transparency (m), pH value and other water environment indicators at each sampling point were measured as water body physical and chemical factors. Transparency was measured using a transparency disk; water temperature, dissolved oxygen and pH value were measured using a portable water quality analyzer.

[0050] When investigating the physical, water temperature and chemical elements of fish habitats, the longitude and latitude of each sampling point were recorded by a handheld GPS device, and the measurement time was recorded. To ensure the accuracy of environmental data, each environmental indicator was randomly measured three times near the sampling point or on the cross section, and the average value was taken as the environmental data of the sampling point, and the measurement time was accurately recorded. Physical elements and other physical and chemical factors are mainly used to analyze the characteristics of fish spawning grounds and nursery habitats, as well as subsequent quantitative analysis of habitat area. Figure 4 shown.

[0051] Step 5. Analyze the conditions of the spawning grounds of schizothorax Based on steps 3 and 4, the location of spawning grounds, spawning time and spawning habitat requirements of schizothorax in the target river section were analyzed and summarized.

[0052] (1) Confirm the location and time of spawning. A total of 562 fish eggs were collected in the target river section from March 19 to April 26, 2024. After identification, the eggs of the heterodont schizothorax, the bibarbelly leaffish and the Lhasa naked schizothorax were collected. Based on the collected fish eggs, a total of 10 schizothorax spawning grounds were confirmed, of which 1 was located in the mainstream of the target river and 9 were located in the river section from the downstream of the main tributaries to the estuary. The spawning grounds of the Lhasa naked schizothorax are widely distributed, and fertilized eggs have been collected in all 10 spawning grounds. There are 3 spawning grounds for the heterodont schizothorax and 1 spawning ground for the bibarbelly leaffish. In general, the spawning grounds of schizothorax such as the heterodont schizothorax, the Lhasa naked schizothorax and the bibarbelly leaffish are distributed in the wide valley sections of the mainstream of the target river, as well as in the downstream and estuary sections of the main tributaries.

[0053] (2) Suitable conditions for spawning of schizothorax The habitat characteristics of the fish spawning grounds determined by the actual collected fish eggs were analyzed. The results showed that the water depth of the spawning grounds ranged from 20-60cm, the flow rate ranged from 0.105-0.581m / s, the water temperature was 7.2-14.7℃, the dissolved oxygen was 7.28-9.54mg / L, the turbidity was 0.54-19.7NTU, and the pH was 7.34-8.56. According to the riverbed particle size analysis, the most suitable bottom particle size range for spawning of schizothorax fish was 2-64mm, followed by 64-256mm.

[0054] The above results show that the spawning grounds of schizothoracine fish are generally in river sections with gravel and sand as the main sediments with a particle size of 2-64mm. The spawning grounds require certain water flow conditions, with a flow rate of 0.2-0.6m / s being more suitable and a water depth of 20-60cm. This type of habitat is mainly distributed near the shore of the wide valley section of the main and tributary rivers of the target rivers, or on the river beaches or backwater bays, or in waters where large tributaries flow into.

[0055] In summary, through the method of the present invention, the spawning location of schizothorax in the lower middle reaches of the target river and its suitable spawning environmental conditions were successfully confirmed, and the precise positioning of schizothorax spawning grounds over a large area was achieved for the first time in China.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for investigating the location and habitat characteristics of spawning grounds of schizothorax in plateau rivers, characterized in that: The steps include: Step 1. Determine the breeding time of schizothorax in the target river section: By consulting the literature, the spawning date of schizothorax was inferred through the reproductive biology characteristics and the daily growth pattern of otoliths of larvae and juveniles in the target river section, and finally the main spawning period of schizothorax in the target river section was determined; Step 2. Preliminary determination of the spawning waters of schizothorax in the target river section: The distribution range was determined based on the temporal and spatial distribution characteristics of schizothorax resources described in the literature, and the river sections where schizothorax spawned were preliminarily determined based on the qualitative description of the habitat characteristics of the spawning grounds and the distribution of broodstock at stage V or VI of gonadal development collected during the mature broodstock survey; Step 3. In situ survey of spawning grounds: Based on steps 1 and 2, design targeted sampling tools according to the spawning characteristics of schizothorax, select representative waters for field surveys, conduct species morphological identification and molecular confirmation of collected eggs and fry, identify the spawning schizothorax species, and infer the spawning time based on early developmental characteristics to confirm the location of the spawning grounds; Step 4. Conduct habitat survey of spawning grounds: Based on the fish spawning grounds determined by the field survey in step 3, a habitat survey is carried out simultaneously to obtain detailed data on environmental factors for spawning of schizothorax fish, clarify the habitat conditions for spawning of schizothorax fish, and analyze key habitat elements and appropriate parameter ranges; Step 5. Analyze and obtain the conditions of the spawning grounds of schizothorax: Based on steps 3 and 4, the location of spawning grounds, spawning time and habitat requirements of schizothorax in the target river section were analyzed and summarized.

2. The method according to claim 1, characterized in that Step 1 is specifically based on the sex body index and the annual variation law of gonad development in reproductive biology. The sex body index refers to the gonad maturity coefficient, that is, the ratio of the fish gonad weight to the body weight. The annual variation law of gonad development refers to the law of the appearance of stage IV, stage V and stage VI gonads in each month of the year in biological research.

3. The method according to claim 1, characterized in that The spatiotemporal distribution characteristics of schizothorax resources in step 2 refer to the spatial distribution of adult and fry of schizothorax; the habitat characteristics of the spawning ground refer to the river bottom quality, water depth and flow velocity characteristics of the target river section.

4. The method according to claim 1, characterized in that: Step 4: Detailed data on spawning environmental factors include: bottom conditions, water flow velocity, water depth, water temperature, dissolved oxygen, transparency, pH value, and longitude and latitude.

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