A method for assessing the initial adaptability of a lake released fish

Abstract

The application discloses a kind of lake release fish initial adaptability evaluation method, it is related to release fish adaptability evaluation technical field.The method comprises the following steps: S1 marking of fish before release;S2 transport and release of marked fish;S3 setting and recapture monitoring of recapture point;S4 processing and data acquisition of recapture fish;S5 release fish initial adaptability evaluation: from spatial adaptability and time adaptability to evaluate the initial adaptability of release fish, spatial adaptability evaluation index includes movement direction and water depth selectivity, time adaptability evaluation index includes initial colonization time and initial feeding time.The application can better obtain the diffusion direction, water depth selectivity, initial colonization time, initial feeding time and other spatial adaptability and time adaptability parameters of artificially bred fish after release, can provide more comprehensive and reliable scientific data for adaptability evaluation of lake artificial propagation release fish, and provide more comprehensive basis for effect evaluation of lake propagation release project.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of evaluation of the adaptability of released fish, and particularly relates to a method for evaluating the initial adaptability of lake released fish. BACKGROUND

[0002] Releasing is an important technical means for the conservation and development of rare native fish resources and the development of aquaculture fisheries, and is widely used at home and abroad. However, despite the large number of releasing activities carried out at home and abroad, the evaluation of the releasing effect is lagging and difficult. This has also led to little direct evidence to prove the success of the releasing activities. Therefore, it is necessary to further strengthen the research and improvement of the evaluation technology of the releasing effect.

[0003] The traditional evaluation of the releasing effect of fish mainly uses the method of marking and recapturing, but there are certain defects in the recapturing method and monitoring indicators. Marking and recapturing is the main research method for evaluating the releasing effect. Through the number, position, time and individual size of the marked released fish recaptured, the survival rate, diffusion distance and growth rate of the released fish are obtained, so as to evaluate the releasing effect. However, due to the rapid diffusion of fish released into natural waters, the potential distribution area is very large, and the recapturing points and frequency are often insufficient due to the limitations of manpower and funds. Most of the releasing activities start recapturing after one month, resulting in very low recapturing quantity, even zero, making it difficult to determine whether most of the released fish have died or not been caught. If the recapturing quantity is relied on to evaluate the releasing effect, it is basically not convincing. Therefore, it is necessary to improve the recapturing monitoring method and monitoring indicators of released fish.

[0004] The initial adaptability of fish entering a new environment is crucial to its survival, but it is rarely concerned. Releasing is generally to transfer artificially bred fish from artificial environment to natural environment, so the released fish will face great environmental differences. Once the released fish successfully adapts to the new environment, it can obtain a high survival rate. Therefore, mastering the initial adaptability of released fish can determine the effect of releasing.

[0005] However, there is no relevant report on the evaluation method of the initial adaptability of released fish at present. SUMMARY

[0006] The present application aims to provide a method for evaluating the initial adaptability of lake released fish, so as to solve the problem of unreasonable recapturing method and monitoring indicators of released fish in the prior art, which leads to the difficulty in effectively carrying out the evaluation of the releasing effect.

[0007] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0008] The application provides a method for evaluating initial adaptability of lake released fish, comprising the following steps:

[0009] S1 marking of fish before release: selecting healthy fish fry or adult fish cultured artificially as marking objects, selecting a marking method with less influence on fish health and behavior according to the size of the fish, and completing marking one week before release;

[0010] S2 transportation and release of fish with marks: transporting the released fish to the release point of the target lake within 1-12 hours before release, randomly selecting 5-10 fish fry before release, and observing the initial filling degree of the digestive tract through dissection; then, measures are taken to reduce the influence of water temperature change before and after release on the released fish, and all the remaining fish are released into the lake as soon as possible after the temperature difference is stable;

[0011] S3 setting of recapture point and recapture monitoring: setting recapture points along the lake shoreline and open water area direction with the release point as the origin, setting one fan-shaped grid recapture point in each level in the same direction, and setting the release origin as a recapture point, the straight-line distance between adjacent recapture points in the same direction is 100-500 m, the water depth of each recapture point is measured, and the same number and type of fishing gear are arranged at each recapture point, the arrangement of the fishing gear is completed within 1-12 hours before release, and the fishery products at each point are collected every day within 7-10 days after release;

[0012] S4 processing and data collection of recaptured fish: the recaptured fish are processed separately according to time and point, whether the recaptured fish is the released fish is determined by whether the fish is marked, and then the released fish is counted, the released fish is dissected, the digestive tract is peeled off for filling degree observation, and the filling degree of the digestive tract of the released fish is classified according to the volume ratio of food in the digestive tract;

[0013] S5 initial adaptability evaluation of released fish: the initial adaptability of the released fish is evaluated from spatial adaptability and temporal adaptability, the spatial adaptability evaluation index includes movement direction and water depth selectivity, and the temporal adaptability evaluation index includes initial colonization time and initial feeding time.

[0014] In the preferred embodiment of the application, in step S1, the marking method includes any one of visible implantation fluorescent marking, T-shaped hanging card marking and micro-metal marking.

[0015] In the preferred embodiment of the application, in step S1, after marking, the health of the marked fish and the marking retention are closely observed during temporary cultivation, sick fish, injured fish and fish with fallen marks are removed in time, and the number of fish finally used for release is accurately checked.

[0016] In another preferred embodiment of the present application, in step S2, when reducing the influence of water temperature change on the released fish before and after release, the following method is adopted: if the released fish is transported by fish fry bag, the fish fry bag is placed in the near-shore lake water to balance the temperature for at least 0.5 h after reaching the release point; if the released fish is transported by water tank or open transport method, ice or sunshade method is adopted after reaching the release point.

[0017] In another preferred embodiment of the present application, in step S3, the fishing gear is put back in place after collecting fish every day, and if damage or loss of the fishing gear is found, the same number and type of fishing gear is replaced in time.

[0018] In another preferred embodiment of the present application, in step S4, the grading range of the degree of stasis is 0-5, wherein 0 indicates that there is no food in the digestive tract, 1, 2, 3 and 4 indicate that the volume ratio of food in the digestive tract is 0-25%, 25-50%, 50-75% and 75-100% respectively, and 5 indicates that the digestive tract is full of food and the digestive tract is swollen.

[0019] In another preferred embodiment of the present application, in step S5, the movement direction is used to reveal the preference of the released fish moving in different directions, and when the average number of released fish recaptured at the lake shore recapture point is more than the average value at the open water area recapture point, the released fish is judged to be near-shore fish; otherwise, it is open water fish.

[0020] In another preferred embodiment of the present application, in step S5, the water depth selectivity refers to the preference of the released fish to the water depth of the lake, and the calculation formula is as follows:

[0021]

[0022] Wherein, S j is the selectivity of the released fish to water layer j, N j is the average number of released fish recaptured at the recapture point in the range of water layer j, m is the total number of water layers, and the value range of water depth selectivity is 0-1, 0 indicating no selection at all and 1 indicating full selection.

[0023] In another preferred embodiment of the present application, in step S5, the initial colonization time refers to the time when the released fish stops continuing migration after being released into the lake; when the number of released fish recaptured on the nth day after release is more than 50% of the recaptured amount on the (n-1)th day after release, it is considered that the nth day after release is the initial colonization time of the released fish.

[0024] In another preferred embodiment of the present application, in step S5, the initial feeding time refers to the time when the released fish starts to feed for the first time after being released into the lake; when the average digestive tract fullness of the released fish on the n+1th day after release is greater than the average fullness on the nth day after release, the nth day after release is considered as the initial feeding time of the released fish.

[0025] Compared with the prior art, the present application has the following beneficial effects:

[0026] (1) The present application innovates the recapture method of released fish. The fan-shaped grid recapture point setting and the recapture time concentrated in the initial period of fish release realize more accurate recapture and higher recapture amount.

[0027] (2) The present application creatively proposes an evaluation index of the initial adaptability of released fish. The adaptability of released fish is evaluated from the combination of spatial adaptability and temporal adaptability, which has the advantages of reliable and accurate evaluation. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a flowchart of the present application;

[0029] Figure 2 is a schematic diagram of the recapture point setting in the present application;

[0030] Figure 3 is a recapture point setting diagram of Qilu carp after release in the embodiment of the present application;

[0031] Figure 4 is a diagram of the daily recapture amount change of Qilu carp fry within 7 days after release in the embodiment of the present application;

[0032] Figure 5 is a diagram of the digestive tract fullness change of Qilu carp fry within 7 days after release in the embodiment of the present application. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The specific embodiments described herein are only used to explain the present application, and are not used to limit the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of the present application.

[0034] As shown in Figure 1 , the present application provides an evaluation method for the initial adaptability of lake released fish, comprising the following steps:

[0035] 1. Marking of fish before release.

[0036] In 2022, a batch of robust and uniformly sized artificially bred Qilu carp fry were selected from a seedling breeding base in Yunnan Province. One week prior to release, the fry were tagged with visible fluorescent markers. After tagging, the fry were temporarily held in net cages, during which time the health of the tagged fish and the retention of the tags were closely monitored, and sick, injured, and tagged fish were promptly removed. The final number of fry available for release was 20,000.

[0037] 2. Transportation and release of tagged fish.

[0038] Three hours before release, tagged fish were packaged in fry bags and transported by truck to the release point in the target lake. Before release, 5-10 fry were randomly selected and dissected to observe the initial filling degree of their digestive tracts. Upon arrival, the fry bags were placed in near-shore lake water for 0.5 hours to allow for temperature equilibration. Monitoring showed that the temperature difference between the water inside the fry bags and the lake water was less than 1°C. The remaining fish were then quickly released artificially into the lake.

[0039] 3. Setting up capture points and monitoring capture.

[0040] Using the release point as the origin, 3-5 layers of fan-shaped grid-like recapture points are set along the left and right shorelines of the lake and the open water area of ​​the lake, such as... Figure 2 As shown. Specifically, in this embodiment, with the release point as the origin, four layers (A, B, C, D) of fan-shaped gridded recapture points are set along the left lake shoreline, right lake shoreline, and open water area of ​​the lake, as shown. Figure 3 As shown in the diagram. One recapture point was set up for each direction and level, with the release origin also serving as a recapture point. The straight-line distance between adjacent recapture points in the same direction was approximately 150-300 meters, and the water depth at each recapture point was measured. Six hours before release, a 10-meter-long, 45-cm-wide, and 33-cm-high fish trap was placed at each recapture point as a fishing gear. For seven days after the fish fry were released, the catch from each point was collected daily. The recapture traps were returned to their original positions after each day's catch. If any traps were found to be damaged or missing, they were promptly replaced with the same number and model.

[0041] 4. Processing and data collection of fish catches.

[0042] The captured fish was processed separately according to time and point. First, whether the captured fish was the released Qilu carp fry was determined by whether it was marked, and counted. Then the released fry was dissected, and the digestive tract was stripped out for observation of the degree of stasis. According to the proportion of food occupying the volume of the digestive tract, the degree of stasis of the released fish was classified. The classification range of the degree of stasis was 0-5, wherein 0 indicated that there was no food in the digestive tract, 1, 2, 3, and 4 indicated that the volume proportion of food in the digestive tract was 0-25%, 25-50%, 50-75%, and 75-100%, respectively, and 5 indicated that the digestive tract was full of food, and the digestive tract was swollen.

[0043] 5. Initial adaptability evaluation of the released fish.

[0044] The initial adaptability of the released Qilu carp fry was evaluated from the aspects of spatial adaptability and temporal adaptability.

[0045] (1) Spatial adaptability index

[0046] Including movement direction and water depth selectivity.

[0047] ① Movement direction

[0048] Used to reveal the preference of the released Qilu carp fry for moving in different directions. When the average number of released fish captured at the lake shore zone capture points was more than that at the open water zone capture points, the released fish was determined to be a near-shore zone fish; otherwise, it was an open water zone fish. The results of the capture showed that the average number of released fish captured at the lake shore zone capture points (A1, B1, C1, D1, A3, B3, C3, and D3) was 3.95 per day, and the average number of released fish captured at the open water zone capture points was 0.36 per day, indicating that the Qilu carp fry was a near-shore zone fish.

[0049] ② Water depth selectivity

[0050] Refers to the preference of the released fish for the water depth of the lake. The calculation formula is as follows:

[0051]

[0052] Wherein, S j is the selectivity of the released fish to water layer j, N j, where is the average number of released fish recaptured at the recapture points within water layer j, and m is the total number of fish in each water layer. The water depth selectivity ranges from 0 to 1 (0 indicates no selection at all, 1 indicates full selection). Based on the measured water depth data from all 13 recapture points, four water layers were defined (≤250cm, 251-350cm, 351-450cm, ≥451cm). The calculation results are shown in Table 1. In the initial stage of release, the Qilu carp fry mainly stayed in waters with a depth of less than 300cm, and after the second day of release, they completely avoided waters with a depth greater than 300cm.

[0053] Table 1. Selectivity of different water layers for Qilu carp fry during the initial release stage.

[0054]

[0055] (2) Time adaptability

[0056] This includes the time of initial settlement and the time of initial feeding.

[0057] ① Initial settlement time

[0058] This refers to the time after released fish cease migrating and begin to settle in the lake for the first time. If the number of released fish recaptured on day n+1 after release is greater than 50% of the number recaptured on day n after release, then day n after release is considered the initial settlement time of the released fish. The recapture results are as follows... Figure 4 As shown, the recapture rate on the 6th day after release was more than 50% of that on the 5th day after release for the first time. Therefore, the 5th day after release can be regarded as the initial settlement time of the released fish.

[0059] ②Time of first feeding.

[0060] This refers to the time when released fish begin feeding for the first time after being released into the lake. If the average digestive tract filling degree of the released fish on day n after release is greater than the average filling degree on day n-1 after release, then day n is considered the time of the first feeding of the released fish. Monitoring results are as follows... Figure 5 As shown, the gastrointestinal tract filling degree of the Qilu carp fry was greater on the 5th day after release than on the 4th day after release, indicating that the 5th day after release was the first feeding time of the released Qilu carp fry, and no 0-level filling degree was observed during the entire monitoring period.

[0061] Based on both spatial and temporal adaptability parameters, artificially bred Qilu carp fry, after being released into lakes, primarily settled in near-shore waters with a depth of less than 300 cm. Initial settlement and resumption of feeding both occurred on the 5th day after release. Under normal circumstances, Qilu carp fry do not die after 4-5 days of starvation. Therefore, it can be determined that artificially released Qilu carp fry achieve a high survival rate, and the Qilu carp propagation and release activities carried out in relevant lakes are effective.

[0062] Therefore, the evaluation method designed by the application can better obtain the diffusion direction, water depth selectivity, initial colonization time, initial feeding time and other spatial and temporal adaptability parameters of artificially bred fish after release, can provide more comprehensive and reliable scientific data for the adaptability evaluation of artificially bred fish in related lakes, and further provide more comprehensive basis for the effect evaluation of lake breeding and releasing project.

[0063] Finally, it should be noted that: the above only for the preferred embodiments of the present application, and not for the limitation of the present application, although the foregoing embodiments of the present application are described in detail, for those skilled in the art, it still can be modified, or part of the technical features of the equivalent replacement, within the spirit and principles of the present application, any modification, equivalent replacement, improvement, etc., should be included in the protection scope of the present application.

Claims

1. A method for assessing the initial adaptability of fish released into lakes, characterized in that, Includes the following steps: S1 Fish tagging before release: Select healthy artificially bred fry or adult fish as the tagging targets. According to the size of the fish, choose any one of the following tagging methods: visible implanted fluorescent tag, T-shaped tag, or micro-metal tag. The tagging should be completed one week before release. S2 Tagged Fish Transportation and Release: Transport the fish to the release point of the target lake 1-12 hours before release, and randomly select 5-10 fry before release to dissect and observe the initial degree of obstruction of the digestive tract; then take measures to reduce the impact of water temperature changes before and after release on the released fish, and release all the remaining fish into the lake as soon as possible after the temperature difference stabilizes. S3 Recapture Point Setup and Monitoring: With the release point as the origin, recapture points are set along the shoreline and open water area of ​​the lake. A fan-shaped grid of recapture points is set up in each direction and at each level. The release origin is also used as a recapture point. The straight-line distance between adjacent recapture points in the same direction is 100-500m. The water depth at each recapture point is measured, and the same number and type of fishing nets are set up at each recapture point. The setting up of the fishing nets is completed within 1-12 hours before the release. The catch at each point is collected every day within 7-10 days after the release. S4 Processing and Data Collection of Recaptured Fish: Recaptured fish were processed separately according to time and location. Whether the recaptured fish were released fish was determined by whether they were marked. The fish were counted and then dissected. The digestive tracts of the recaptured fish were dissected and the degree of filling was observed. The degree of filling of the digestive tracts of the released fish was graded according to the proportion of food occupying the volume of the digestive tract. S5 Initial Adaptability Assessment of Released Fish: The initial adaptability of released fish is assessed from two aspects: spatial adaptability and temporal adaptability. The spatial adaptability assessment indicators include movement direction and water depth selectivity, while the temporal adaptability assessment indicators include initial settlement time and initial feeding time.

2. The method for assessing the initial adaptability of fish released into lakes according to claim 1, characterized in that, In step S1, after the tagging is completed, the health of the tagged fish and the retention of the tags are closely observed during the temporary holding period. Sick fish, injured fish and fish whose tags have fallen off are removed in a timely manner, and the number of fish ultimately used for release is accurately verified.

3. The method for assessing the initial adaptability of fish released into lakes according to claim 1, characterized in that, In step S2, to reduce the impact of water temperature changes before and after release on the released fish, the following methods are adopted: If fish fry bags are used to transport the released fish, after arriving at the release point, the fish fry bags are placed in the near-shore lake water to allow for temperature equilibration, and the equilibration time is at least 0.5 hours; if water tanks or open transport methods are used to transport the released fish, ice or sunshade methods are adopted after arriving at the release point.

4. The method for assessing the initial adaptability of fish released into lakes according to claim 1, characterized in that, In step S3, the fishing nets are returned to their original positions after the catch is collected each day. If any fishing nets are found to be damaged or missing, they are promptly replaced with fishing nets of the same quantity and type.

5. The method for assessing the initial adaptability of fish released into lakes according to claim 1, characterized in that, In step S4, the degree of filling is graded from 0 to 5. Grade 0 indicates that there is no food in the digestive tract. Grades 1, 2, 3, and 4 indicate that the volume of food in the digestive tract is 0-25%, 25-50%, 50-75%, and 75-100%, respectively. Grade 5 indicates that the digestive tract is full of food and the digestive tract is distended.

6. The method for assessing the initial adaptability of fish released into lakes according to claim 1, characterized in that, In step S5, the direction of movement is used to reveal the preference of the released fish to move in different directions. When the average number of released fish recaptured at the shoreline recapture point exceeds the average number of recapture points in the open water area of ​​the lake, the released fish are judged to be nearshore fish; otherwise, they are open water fish.

7. The method for assessing the initial adaptability of fish released into lakes according to claim 1, characterized in that, In step S5, the water depth selectivity refers to the preference of the released fish for lake water depth, and the calculation formula is as follows: S j =N j / j Among them, S j To ensure the selectivity of released fish for water layer j, N j is the average number of released fish caught at the recapture point within water layer j, m is the total number of water layers, and the water depth selectivity ranges from 0 to 1, where 0 means no selection and 1 means full selection.

8. The method for assessing the initial adaptability of fish released into lakes according to claim 1, characterized in that, In step S5, the initial settlement time refers to the time when the released fish stop migrating after being released into the lake and begin to settle for the first time. When the number of fish recaptured on day n after release is greater than 50% of the number recaptured on day n-1 after release, day n after release is considered the initial settlement time of the released fish.

9. The method for assessing the initial adaptability of fish released into lakes according to claim 1, characterized in that, In step S5, the initial feeding time refers to the time when the released fish begin to feed for the first time after being released into the lake; When the average gastrointestinal tract filling degree of the released fish on the (n+1)th day after release is greater than the average filling degree on the nth day after release, the nth day after release is considered to be the time when the released fish first began feeding.

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