Method for estimating effective accumulated temperature of spawning and breeding of fishes laying drifting eggs

Abstract

The invention discloses a method for estimating the effective accumulated temperature of spawning and breeding of fishes laying drifting eggs. The method comprises the following steps: acquiring daily average water temperature data of each year in a spawning site of target fishes laying drifting eggs; determining the time when the target fishes laying the drifting eggs begin to lay eggs in the spawning site in each year; the minimum value of the daily average water temperature of all years is determined; the minimum value of the daily average water temperature of each year and the occurrence date of the minimum value are determined; determining the lowest critical water temperature required by the oviposition and reproduction of the target fishes laying the drifting eggs; determining a possible distribution range of biological zero degrees; respectively calculating effective accumulated temperature required by spawning and breeding under different assumed biological zero degrees in different years; variable coefficients of the effective accumulated temperature in all evaluation years under different assumed biological zero-degree conditions are calculated respectively; determining the real biological zero degree of the target fish according to the variable coefficient; and determining the minimum effective accumulated temperature required by egg laying and breeding of the target fish according to the biological zero degree. According to the method, the effective accumulated temperature required by spawning and breeding of the fishes laying the drifting eggs is estimated.

Description

Technical Field

[0001] This invention relates to the field of ecology, and more particularly to a method for estimating the effective accumulated temperature for spawning and reproduction in drifting fish. Background Technology

[0002] Water temperature is both a necessary and limiting condition for spawning in drifting fish, which spawn within their suitable spawning temperature range. Water temperature plays a crucial role in influencing gonadal development, steroid hormone expression, ovulation inhibition, advancing or delaying spawning time, and altering embryo survival rates. For drifting fish, achieving the critical spawning temperature and meeting the pre-spawning effective accumulated temperature conditions are both key factors for successful spawning. The effective accumulated temperature for fish reproduction refers to the cumulative temperature above the biological zero point (the minimum effective temperature threshold required for development or reproduction) during the fish's reproductive process, measured in °C*d. Obtaining effective accumulated temperature data is of great significance for predicting peak spawning periods, assessing the suitability of reproductive environments, implementing artificial breeding control, and conducting climate change research.

[0003] In acquiring effective accumulated temperature data, the key is to determine the biological zero point required for spawning and reproduction in different fish species. This typically requires rigorous indoor temperature control experiments. However, these experiments face several challenges: 1) Obtaining suitable subjects is difficult (e.g., nationally protected animals and fish species unique to the upper Yangtze River whose artificial breeding techniques are not yet fully developed are hard to introduce into the laboratory); 2) Precise temperature control is challenging, and the water temperature process curve is difficult to accurately match with the natural water temperature process curve, increasing the difficulty of experimental design; 3) Limited indoor experimental conditions increase fish stress or maladaptive behaviors, potentially affecting the accuracy of the final results. Therefore, there is an urgent need to develop a method based on field measurements to statistically determine the biological zero point and effective accumulated temperature for fish that lay drifting eggs. Summary of the Invention

[0004] In view of this, this application proposes a method for estimating the effective accumulated temperature for spawning and reproduction of drifting-egg fish, which can provide support for predicting the peak spawning period of fish, assessing the suitability of the breeding environment, implementing artificial breeding regulation, and carrying out climate change research.

[0005] According to one aspect of this application, this application provides a method for estimating the effective accumulated temperature for spawning and reproduction in drifting-egg-laying fish, the method comprising:

[0006] Obtain the daily average water temperature data of the spawning grounds of drifting target fish species for each year;

[0007] Determine the start time of spawning in the spawning grounds for target fish species that lay drifting eggs in each year;

[0008] Determine the minimum daily average water temperature for all years;

[0009] Determine the minimum daily average water temperature for each year and the date on which it occurs;

[0010] Determine the minimum critical water temperature required for spawning and reproduction of target fish species that lay drifting eggs;

[0011] Based on the minimum daily average water temperature over all years and the minimum critical water temperature required for the spawning and reproduction of the target fish, the possible distribution range of biological zero is determined.

[0012] Based on the minimum daily average water temperature and its occurrence date for each year, the possible distribution range of biological zero, and the time when the target fish begin spawning in the spawning grounds in each year, the effective accumulated temperature required for spawning and reproduction under different hypothetical biological zero (possible biological zero) conditions in different years is calculated.

[0013] Calculate the coefficient of variation of effective accumulated temperature under different hypothetical biological zero conditions for all assessment years;

[0014] The true biological zero of the target fish is determined based on the magnitude of the coefficient of variation.

[0015] Based on the established biological zero, determine the minimum effective accumulated temperature required for the target fish to spawn and reproduce.

[0016] Preferably, obtaining the daily average water temperature data of the spawning grounds of drifting target fish includes: 1) determining the distribution location of the main spawning grounds of drifting target fish based on early fish resource surveys and on-site catch surveys and dissections; 2) obtaining water temperature data at different measurement times in each year at hydrological stations within or near the spawning grounds of the target fish through data collection or on-site water temperature measurements, with the years of water temperature data acquisition being at least 15 years to meet basic statistical requirements; 3) calculating the daily average water temperature using the arithmetic mean method based on the water temperature data at different times.

[0017] Preferably, determining the start time of spawning for target fish species that lay drifting eggs in the spawning grounds in each year includes: 1) determining the specific start time of spawning for target fish species that lay drifting eggs in each year based on the results of early fish resource field surveys. The early fish resource survey should begin before the target fish spawn; 2) for years lacking early fish survey data, the specific start time of spawning for target fish species can be determined based on the spawning time of target fish species obtained from the results of early fish resource field surveys and the minimum critical water temperature required for spawning.

[0018] Preferably, the minimum value of the daily average water temperature for all years is determined, that is: the minimum value of the daily average water temperature data for each year of the obtained spawning grounds of drifting target fish is taken.

[0019] Preferably, determining the minimum critical water temperature required for the spawning and reproduction of target fish species that lay drifting eggs includes: determining the minimum critical water temperature required for the spawning and reproduction of fish by using comparative analysis methods based on existing monitoring data or indoor experiments.

[0020] Preferably, determining the possible distribution range of biological zero includes:

[0021] 1) Based on the minimum daily average water temperature for all assessment years, determine the lower limit of the possible distribution range of biological zero temperature for the target fish species, i.e., BZ. lower ;

[0022] 2) Based on the minimum critical water temperature required for spawning and reproduction of the target fish species, determine the upper limit of the possible distribution range of biological zero temperature for the target fish species, i.e., BZ. upper ;

[0023] 3) The possible distribution range of biological zero is: [BZ lower, BZ upper ]

[0024] Preferably, the calculation of the effective accumulated temperature required for spawning and reproduction at different biological zero degrees Celsius in different years includes:

[0025] 1) Determine the starting point for calculating effective accumulated temperature based on the date on which the minimum daily average water temperature first occurs in each year;

[0026] 2) Determine the endpoint for calculating effective accumulated temperature based on the time when the target fish begin spawning in the spawning grounds each year;

[0027] 3) Based on the above, integrating the possible distribution range of biological zero, the effective accumulated temperature for different assessment years under different hypothetical biological zero is calculated using the following formulas:

[0028] Formula 1:

[0029]

[0030] In the above formula, EAW i WT represents the effective accumulated temperature under different hypothetical biological zero temperatures in year i. i,s WT is the average water temperature on the day (day s) on which the minimum daily average water temperature first occurs in year i. i,e Let BZ be the average water temperature on day e, the date the target fish begins spawning in the spawning grounds in year i. [BZ lower BZ upperThe formula is to substitute the values ​​of the biological zero-degree range into the above formula to calculate the effective accumulated temperature of the target fish in each year from the first occurrence of the minimum daily average water temperature (day s) to the start of spawning (day e) under different assumed biological zero degrees.

[0031] Preferably, the coefficient of variation of the effective accumulated temperature under different hypothetical biological zero conditions is calculated for all assessment years. This includes calculating the effective accumulated temperature for different years under different hypothetical biological zero conditions using the coefficient of variation formula, i.e.:

[0032] Formula 2-4:

[0033]

[0034] In the above formula, CV BZ The coefficient of variation of effective accumulated temperature under different hypothetical biological zero conditions over all assessment years; one value corresponds to one biological zero. BZ The standard deviation of effective accumulated temperature under different hypothetical biological zero conditions over all assessment years is given, with one value corresponding to one biological zero. The effective accumulated temperature under different hypothetical biological zero conditions is the average value over all assessment years; one biological zero corresponds to one value; n is the total number of assessment years.

[0035] Preferably, determining the true biological zero of the target fish includes comparing the magnitude of the coefficient of variation under different biological zero conditions, and, based on the principle of long-term adaptation of fish to the ecological environment, identifying the biological zero with the smallest coefficient of variation as the true biological zero of the target fish.

[0036] Preferably, determining the minimum effective accumulated temperature required for the spawning and reproduction of the target fish includes determining the minimum effective accumulated temperature required for the spawning and reproduction of the target fish based on the determined true biological zero temperature of the target fish.

[0037] This application discloses a method for estimating the biological zero point and effective accumulated temperature for spawning and reproduction in fish species that lay drifting eggs. The method includes: acquiring multi-year daily average water temperature data of the target fish's spawning grounds; determining the start time of spawning in each year; statistically analyzing the minimum daily average water temperature and its occurrence date for all years; determining the minimum critical water temperature required for spawning; determining the possible distribution range of the biological zero point based on the above data; calculating the effective accumulated temperature required for spawning in each year under different assumed biological zero points; calculating the coefficient of variation of the effective accumulated temperature over all years under each assumed condition; determining the true biological zero point according to the principle of minimizing the coefficient of variation; and further determining the minimum effective accumulated temperature required for spawning and reproduction. Based on field measurement data, this invention can statistically estimate the biological zero point and effective accumulated temperature of fish species that lay drifting eggs, and is applicable to fields such as predicting peak spawning periods and assessing the suitability of reproductive environments.

[0038] Other features and advantages of this application will be described in detail in the following detailed description section. Attached Figure Description

[0039] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application, and the illustrative embodiments and descriptions thereof are used to explain this application. In the drawings:

[0040] Figure 1 This application provides a method for estimating the effective accumulated temperature for spawning and reproduction in drifting-egg fish.

[0041] Figure 2 The distribution locations of the main spawning grounds of the longfin gudgeon in the main stream section of the upper reaches of the Yangtze River within the protected area, as shown in the specific implementation case;

[0042] Figure 3 This represents the relationship between the coefficient of variation of effective accumulated temperature under different hypothetical biological zero conditions and biological zero in all assessment years in a specific implementation case. Detailed Implementation

[0043] It should be noted that, where there is no conflict, the embodiments and features of each embodiment in this application can be combined with each other.

[0044] This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0045] This invention proposes a method for estimating the biological zero point and effective accumulated temperature for spawning and reproduction in fish that lay drifting eggs. This includes determining the possible distribution range of the biological zero point, calculating the effective accumulated temperature required for spawning and reproduction under different hypothetical biological zero points (possible biological zero points) in different years, calculating the coefficient of variation of the effective accumulated temperature under different hypothetical biological zero point conditions across all assessment years, determining the true biological zero point of the target fish, and determining the minimum effective accumulated temperature required for spawning and reproduction of the target fish. This invention covers the entire process of statistically determining the biological zero point and effective accumulated temperature of fish based on field measurement data, solving the previous problem of difficulty in estimating the biological zero point and effective accumulated temperature of fish.

[0046] This invention proposes a method for estimating the effective accumulated temperature for spawning and reproduction in drifting-egg fish, comprising the following steps:

[0047] Step 1: Using early fish resource surveys and on-site catch dissection methods, determine the main spawning grounds of the target fish species that lay drifting eggs. Then, through data collection or on-site water temperature measurements, obtain water temperature data from hydrological stations within or near the spawning grounds for different times each year. The years for which water temperature data is obtained must be at least 15 years to meet basic statistical requirements. Based on this, calculate the daily average water temperature using the arithmetic mean method from the water temperature data at different times.

[0048] Step 2: Based on the results of early fish resource field surveys or by combining the time of fish spawning and the time of occurrence of the minimum critical water temperature required for fish spawning, directly determine or deduce the time when the target fish species that lay drifting eggs begin spawning in the spawning grounds in each year.

[0049] Step 3: Compare and statistically analyze the daily average water temperature data of the target fish spawning grounds or nearby areas for each year to determine the minimum daily average water temperature for all assessment years.

[0050] Step 4: Through comparative analysis, determine the minimum daily average water temperature for each assessment year and the date on which it occurs;

[0051] Step 5: Based on existing monitoring data or indoor experiments, use comparative analysis to determine the minimum critical water temperature required for the spawning and reproduction of target fish species that lay drifting eggs. Fish will not spawn when the water temperature is below this critical temperature.

[0052] Step 6: Based on the minimum daily average water temperature for all years and the minimum critical water temperature required for the spawning and reproduction of the target fish, comprehensively determine the possible distribution range of biological zero (assuming the distribution range of biological zero).

[0053] Step 7: Based on the minimum daily average water temperature and its occurrence date for each year, the possible distribution range of biological zero, and the time when the target fish begin spawning in the spawning grounds in each year, calculate the effective accumulated temperature required for spawning and reproduction under different hypothetical biological zero (possible biological zero) conditions in different years.

[0054] Step 8: Based on the effective accumulated temperature calculated under different hypothetical biological zero conditions in different years, use the coefficient of variation formula to calculate the coefficient of variation of the effective accumulated temperature under different hypothetical biological zero conditions in all evaluation years.

[0055] Step 9: By comparing the magnitude of the coefficient of variation under different biological zero conditions, and based on the principle of long-term adaptation of fish to the ecological environment and the principle of minimizing the coefficient of variation, determine the true biological zero of the target fish.

[0056] Step 10: Based on the established biological zero, determine the minimum effective accumulated temperature required for the target fish to spawn and reproduce.

[0057] This application provides a method for estimating the effective accumulated temperature for spawning and reproduction in drifting-egg fish, comprising the following steps:

[0058] Obtain the daily average water temperature data of the spawning grounds of drifting target fish species for each year;

[0059] Determine the time when the target fish species begin spawning in the spawning grounds each year;

[0060] Determine the minimum daily average water temperature for all years;

[0061] Determine the minimum daily average water temperature for each year and the date on which it occurs;

[0062] Determine the minimum critical water temperature required for the target fish species to spawn and reproduce;

[0063] The possible range of biological zero is determined based on the minimum and lowest critical water temperatures of the daily average water temperatures over all years.

[0064] Calculate the effective accumulated temperature required for oviposition and reproduction under different hypothetical biological zero temperatures in different years;

[0065] Calculate the coefficient of variation of effective accumulated temperature under different hypothetical biological zero conditions for all assessment years;

[0066] Based on the principle of minimizing the coefficient of variation, the true biological zero of the target fish is determined;

[0067] Based on the stated biological zero degree, determine the minimum effective accumulated temperature required for the target fish to spawn and reproduce.

[0068] The acquisition of daily average water temperature data includes:

[0069] Identify the location of the main spawning grounds of the target fish species;

[0070] Collect annual water temperature data from hydrological stations within or near the spawning grounds, with a data period of no less than 15 years;

[0071] The daily average water temperature was calculated using the arithmetic mean method.

[0072] The methods for determining the start of spawning include:

[0073] Determined directly based on the results of early field surveys of fish resources;

[0074] Alternatively, it can be deduced by combining the time required for the minimum critical water temperature to occur during spawning.

[0075] According to the method of claim 1, the lower limit of the possible distribution range of the biological zero degree is the minimum value of the daily average water temperature of all years, and the upper limit is the lowest critical water temperature minus 1°C.

[0076] The minimum effective accumulated temperature is the minimum value of the effective accumulated temperature in each year at true biological zero.

[0077] Implementation Case:

[0078] This example uses the longfin gudgeon (a national second-class protected animal that lays drifting eggs) in the main stream of the Yangtze River Rare and Endemic Fish National Nature Reserve as the target fish species for evaluation. The method and steps proposed in this invention are used to detail the estimation process of its biological zero point and the effective accumulated temperature required for spawning and reproduction.

[0079] Step 1) Obtain daily average water temperature data for the spawning grounds of drifting target fish species. From 2019 to 2024, an early resource survey of drifting fish species was conducted at the Yibin, Hejiang, and Jiangjin sections of the upper Yangtze River protected area. The spawning distribution location was estimated based on the egg development period of *Gyromitra esculenta* and the average flow velocity at each sampling section. Based on this, combined with the dissection results of catches at each estimated spawning ground, the main spawning grounds of *Gyromitra esculenta* in the main stream section of the upper Yangtze River protected area were determined. It was found that the main spawning grounds of *Gyromitra esculenta* were mainly distributed in the Rongshan Town section of Luzhou, the Jingangtuo section of Chongqing, and the Youxi Town section, accounting for 5.41%, 24.42%, and 42.62% of the total spawning scale of all *Gyromitra esculenta* spawning grounds, respectively. Figure 2 Based on the location of the main spawning grounds, we checked whether there were any hydrological stations in or near the main spawning grounds. The results showed that there was a key hydrological station near the spawning grounds—the Zhutuo Hydrological Station. We then reviewed the historical water temperature data of this station and obtained the daily water temperature data at 8:00 and 16:00 from 2002 to 2024. We then used the arithmetic mean method to obtain the average daily water temperature data for each year.

[0080] Step 2) Determining the spawning start time of drifting target fish species in each year's spawning grounds: Based on the results of the early resource replenishment survey of drifting fish conducted at the Jiangjin section (the monitoring section closest to the main spawning grounds) from 2019 to 2024, the spawning start time of *Gyrodon brevicaulis* in the main spawning grounds was obtained from 2019 to 2024 (generally around March 20th, when the water temperature reaches 16℃ or above). Simultaneously, early fish resource data from the Jiangjin section from 2002 to 2018 were collected and compiled. Combined with the spawning time of *Gyrodon brevicaulis* obtained from the early fish resource survey results from 2019 to 2024, and the minimum critical water temperature required for spawning, the specific spawning start time of *Gyrodon brevicaulis* in each year from 2002 to 2018 was determined.

[0081] Step 3) Determine the minimum daily average water temperature for all years. Based on the daily average water temperature data of Zhutuo Hydrological Station from 2002 to 2024, the minimum daily average water temperature for the above years is 7.1℃.

[0082] Step 4) Determine the minimum daily average water temperature and its occurrence date for each year. Based on the daily average water temperature data of the Zhutuo Hydrological Station from 2002 to 2024, the minimum daily average water temperature and its occurrence date for each year at the Zhutuo Hydrological Station are obtained. For example, the minimum daily average water temperature in 2004 occurred on February 1, 2004, at 9.2℃. Meanwhile, the minimum water temperature in some years spans across years. For example, the minimum daily average water temperature in 2003 occurred on December 28, 2002, at 9.2℃. This date will be considered the date of occurrence of the minimum daily average water temperature in 2003, and thus the starting date for calculating the effective accumulated temperature for the year 2003.

[0083] Step 5) Determine the minimum critical water temperature required for the spawning and reproduction of the target fish species that lay drifting eggs. Based on the results of the early resource survey of drifting fish conducted in the Yibin, Hejiang and Jiangjin sections of the upper Yangtze River protected area from 2019 to 2024, and combined with existing published literature on the habitat conditions required for the spawning and reproduction of the longfin gudgeon, the minimum critical water temperature required for the spawning and reproduction of the longfin gudgeon is determined to be 16℃. Below this temperature, the longfin gudgeon will not lay eggs under natural conditions.

[0084] Step 6) Determine the possible range of biological zero. Based on Step 3, the lower limit of biological zero for longfin gudgeon is 7℃; determine the biological zero at which drifting egg-laying fish begin gonad development, and determine the minimum effective accumulated temperature required for spawning and reproduction of drifting egg-laying fish; based on Step 6, the upper limit of biological zero for longfin gudgeon is 15℃ (16℃-1℃, fish gonad maturation requires a water temperature process); therefore, the range of biological zero BZ is [7℃, 15℃].

[0085] Step 7) Calculate the effective accumulated temperature required for spawning and reproduction under different hypothetical biological zero (possible biological zero) conditions in different years. Determine the starting point for calculating the effective accumulated temperature based on the date on which the minimum daily average water temperature first occurs in each year; determine the ending point for calculating the effective accumulated temperature based on the time when the target fish begins spawning in the spawning grounds in each year; based on the above starting point, ending point, and the range of biological zero (BZ), calculate the effective accumulated temperature required for spawning and reproduction under different hypothetical biological zero (possible biological zero) conditions in different years using Formula 1 (Table 1).

[0086] Table 1. Calculation results of effective accumulated temperature required for spawning and reproduction under different hypothetical biological zero (possible biological zero) conditions in different years (data in the table, unit: ℃*d).

[0087]

[0088] Step 8) Calculate the coefficient of variation of effective accumulated temperature under different hypothetical biological zero conditions across all assessment years. Based on the results of Step 7 (Table 1 data), use Formula 2-4 to calculate the coefficient of variation of effective accumulated temperature under different hypothetical biological zero conditions across all assessment years. Figure 3 ).

[0089] Step 9) Determine the true biological zero of the target fish. According to the results of Step 8, the coefficient of variation is the smallest when the biological zero is 7°C, indicating that the true biological zero of the longfin gudgeon is about 7°C.

[0090] Step 10) Determine the minimum effective accumulated temperature required for the target fish to spawn and reproduce. According to Step 9, when the biological zero is about 7°C, the minimum effective accumulated temperature required for the longfin gudgeon to spawn and reproduce is 327.8°C*d (bold numbers in Table 1).

[0091] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for estimating the effective accumulated temperature for spawning and reproduction in drifting-egg fish, characterized in that, The method includes: Obtain the daily average water temperature data of the spawning grounds of drifting target fish species for each year; Determine the start time of spawning in the spawning grounds for target fish species that lay drifting eggs in each year; Determine the minimum daily average water temperature for all years; Determine the minimum daily average water temperature for each year and the date on which it occurs; Determine the minimum critical water temperature required for spawning and reproduction of target fish species that lay drifting eggs; Determine the possible distribution range of biological zero; Calculate the effective accumulated temperature required for oviposition and reproduction under different biological hypotheses in different years; Calculate the coefficient of variation of effective accumulated temperature under different hypothetical biological zero-degree conditions for all assessment years; Determine the true biological zero of the target fish based on the coefficient of variation; The minimum effective accumulated temperature required for spawning and reproduction of the target fish species is determined based on their actual biological zero temperature.

2. The method for estimating the effective accumulated temperature for spawning and reproduction in drifting-egg-laying fish according to claim 1, characterized in that, Obtaining the daily average water temperature data of the spawning grounds of drifting target fish species for each year includes determining the location of the main spawning grounds of the target fish species and obtaining the daily average water temperature data of the river sections within or near the main spawning grounds.

3. The method for estimating the effective accumulated temperature for spawning and reproduction in drifting-egg-laying fish according to claim 1, characterized in that, The possible range of biological zero is determined based on the minimum daily average water temperature over all years and the minimum critical water temperature required for the spawning and reproduction of the target fish species.

4. The method for estimating the effective accumulated temperature for spawning and reproduction in drifting-egg fish according to claim 1, characterized in that, Calculate the effective accumulated temperature required for spawning and reproduction under different biological hypotheses for different years, including: Based on the minimum daily average water temperature and its occurrence date for each year, the possible distribution range of biological zero, and the time when the target fish begin spawning in the spawning grounds in each year, the effective accumulated temperature required for spawning and reproduction under different assumed biological zero conditions in different years is calculated.

5. The method for estimating the effective accumulated temperature for spawning and reproduction in drifting-egg fish according to claim 1, characterized in that, Determining the true biological zero of a target fish based on the coefficient of variation includes: By comparing the coefficients of variation under different biological zero conditions, and based on the principle of long-term adaptation of fish to the ecological environment, the biological zero with the smallest coefficient of variation is identified as the true biological zero of the target fish.

6. The method for estimating the effective accumulated temperature for spawning and reproduction in drifting-egg-laying fish according to claim 1, characterized in that, Based on the established biological zero temperature of the target fish species, the minimum effective accumulated temperature required for spawning and reproduction of the target fish species is determined through corresponding analysis.

7. The method for estimating the effective accumulated temperature for spawning and reproduction in drifting-egg fish according to claim 1, characterized in that: Based on points 3, 4, and 5 above, the biological zero point at which drifting-egg-laying fish begin gonadal development is determined, and based on point 6, the minimum effective accumulated temperature required for spawning and reproduction in drifting-egg-laying fish is determined.

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