Device and method for trapping young tilapia mossambica

Abstract

The invention discloses a method for efficiently trapping young tilapia mossambica. The method is mainly composed of specially-made baits and an improved ground cage. The bait is prepared from the following components: 20% of silkworm chrysalis meal, 20% of acete chinensis meal, 20% of earthworm powder, 12% of wheat germ powder, 11% of lamellar algae powder, 10% of snowflake powder, 5% of vital gluten and 2% of vanillin. The content of animal-derived protein in the bait is increased, so that strong fishy smell can be quickly diffused after the bait enters water; and the flaky algae powder, the snowflake powder and the wheat germ powder can form a suspended atomization belt around the bait, so that the bait is continuously peeled off, and the fish luring and retaining effects are better. The vanillin is added, so that the bait emits sweet milk fragrance, and surrounding tilapia mossambica can be effectively attracted. The following improvements are made on the ground cage: an anti-escape design is added; a bait bag is hung near the fish inlet; the space of a fish collecting area is expanded, so that the capturing efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of marine fishing, and particularly relates to a device and method for trapping juvenile Oreochromis niloticus Background Art

[0002] Oreochromis niloticus is a typical invasive fish species with strong territorial awareness, high environmental adaptability and reproductive ability, a wide diet, and can even prey on the eggs and juveniles of other fish species, posing a serious threat to the structure and function of the local aquatic ecosystem.

[0003] Oreochromis niloticus is a substrate-spawning tilapia with a relatively short sexual maturity time, having the habits of nest-digging and fry-guarding, and relatively strong territorial awareness (Cummings et al., 2017). The fertilized eggs need 2 - 3 days to hatch, and the broodstock will protect the juveniles for about one month. If the conditions are suitable, the broodstock will carry out the next round of reproduction (Gophen, 2016), and it can carry out the next spawning in as short as 6 to 7 days (Coward & Bromage, 2000). According to the literature report (Coward & Bromage, 2000), under suitable environmental conditions and abundant food, Oreochromis niloticus spawns on average once every 26 days. The high frequency of spawning increases the reproductive potential of Oreochromis niloticus and is conducive to its rapid population expansion.

[0004] To effectively control the wild population of Oreochromis niloticus, eradicating its juveniles has become one of the key strategies. Currently, physical trapping methods are generally used to control the number of wild Oreochromis niloticus (Zhang Min et al., 2023; Yu Guilan et al., 2024). However, in the above methods, no description of specifically controlling the juveniles of Oreochromis niloticus is mentioned. Summary of the Invention

[0005] The present invention provides a method for trapping juvenile Oreochromis niloticus. The purposes are, firstly, to provide a new trapping bait formula, and secondly, to provide a new type of cage net. The trapping bait formula has a relatively low cost, relatively small dosage, high coagulation degree in water and is not easy to disintegrate, and has a long service time, and has high palatability to juvenile Oreochromis niloticus; the new type of cage net can overcome the defect in the prior art that it cannot specifically trap juvenile Oreochromis niloticus. Integrating the above two key technologies can greatly improve the trapping efficiency of juvenile Oreochromis niloticus.

[0006] To solve the above technical problems, the present invention provides the following technical solutions:

[0007] A device for trapping juvenile Oreochromis niloticus, comprising a juvenile fish trapping area (1) and a juvenile fish aggregation area (2). The juvenile fish trapping area (1) and the juvenile fish aggregation area (2) are connected by a funnel-shaped internal connection channel (4). The juvenile fish trapping area (1) includes a funnel-shaped juvenile fish inlet (8), a lead weight at the fish inlet (7), a circular frame at the end of the fish inlet (5), a flexible plastic sheet (6), and a bait bag (3). The lead weight at the fish inlet (7) is sewn on the nylon net below the juvenile fish inlet. The circular frame at the end of the fish inlet (5) is sewn at the end of the juvenile fish inlet. The flexible plastic sheet (6) is perforated and fixed to the circular frame at the end of the fish inlet (5) by cable ties. The bait bag (3) is fixed to the nylon net by its own binding rope. Each section of the fishing cage is connected by a funnel-shaped internal connection channel (4). The last section of the juvenile fish aggregation area uses an enlarged circular frame, and a concrete counterweight (10) is installed in the net bag inside the tail end of the trapping device.

[0008] A device for trapping juvenile Oreochromis niloticus, comprising a frame, a net surface, and a detachable bait bag. The frame is sized 25 cm × 25 cm × 5 m. The 25-cm frame can provide sufficient trapping space. The mesh size of the net surface is 4 mm (the body length of the trapped juvenile fish is concentrated between 1.0 cm and 5.0 cm, and the 4-mm mesh is not likely to cause them to escape). A counterweight is fixed to the lower side of the fish inlet. The fish inlet is designed as a downward-inclined funnel-shaped one-way inlet with a width of 10 cm. A flexible plastic sheet is installed at the end of the inlet. The internal connection of the trapping device uses a funnel-shaped structure that is wider at the top and narrower at the bottom. A detachable bait bag is provided at the fish inlet in the middle of the trapping device. The last section of the frame is made into a cylindrical shape using a circular frame to increase the fish aggregation space and improve the trapping efficiency; the tail gradually converges to facilitate the removal of the catch.

[0009] Furthermore, the frame is made of stainless steel; the net surface is made of nylon or polyethylene. The bait bag is a rectangular nylon mesh bag with a mesh size of 2.5 mm and a size of 15 cm × 10 cm. The front and middle parts of the frame are square, and the tail is circular.

[0010] A method for trapping juvenile Oreochromis niloticus specifically includes the following operating steps:

[0011] S1. Select the trapping location and time: Select a shallow water area (water depth 0.5m - 2m) with sandy or muddy bottom, gentle slope (slope less than 45°), and sufficient sunlight to set up trapping points; According to the water temperature change during the day, the water temperature starts to rise around 8:00 am, and the juvenile Oreochromis niloticus become active and start to actively feed. Therefore, set the starting time for placing the trapping device at 8:00 am, and the time for retrieving the trapping device depends on the season. During the breeding season of Oreochromis niloticus (usually from May to October), the harvesting time is set at 20:00 on the same day; During the non-breeding season of Oreochromis niloticus (usually from November to April of the following year), the harvesting time is set at 8:00 am the next day;

[0012] S2. Prepare the trapping bait: Mix shrimp powder, earthworm powder, silkworm pupa powder, and flake algae powder evenly, and stir-fry in a pot until there is a mixed fragrance; After cooling the above raw materials, mix them evenly with wheat germ powder, snowflake powder, wheat gluten powder, and vanillin, pour in an appropriate amount of water, let it stand for 3 minutes to wait for the bait to fully absorb the water, then stir quickly to make the bait form into a ball, and put it into the bait bag;

[0013] S3. Place the trapping bait: Determine the amount of trapping bait according to the background resource quantity of Oreochromis niloticus in the trapping water area, and tie the bait bag containing the trapping bait to the bait bag fixing rope inside the trapping device;

[0014] S4. Install the trapping device: Fix one end of the trapping device to the shore through a rope, and throw the other end into the water area for trapping juvenile Oreochromis niloticus, and place each trapping device at an interval of 10m;

[0015] S5. Harvest: Quickly lift the trapping device out of the water, untie the knot at the tail, and pour the juvenile Oreochromis niloticus out from the tail of the trapping device.

[0016] Furthermore, the formula of the trapping bait in steps S2 and S3 includes the following components: silkworm pupa powder, shrimp powder, earthworm powder, wheat germ powder, flake algae powder, snowflake powder, wheat gluten powder, and vanillin; By mass fraction, the mass percentages of the above components are respectively: silkworm pupa powder 20%, shrimp powder 20%, earthworm powder 20%, wheat germ powder 12%, flake algae powder 11%, snowflake powder 10%, wheat gluten powder 5%, vanillin 2%. Mix shrimp powder, earthworm powder, silkworm pupa powder, and flake algae powder evenly, stir-fry in a pot until there is a mixed fragrance, then cool and mix evenly with wheat germ powder, snowflake powder, wheat gluten powder, and vanillin, pour in an appropriate amount of water, let it stand for 3 minutes to wait for the bait to fully absorb the water, then stir quickly to make the bait form into a ball. When using, first put the bait ball into the bait bag, and then hang the bait bag into the trapping device to trap the juvenile Oreochromis niloticus.

[0017] Furthermore, the silkworm pupa powder is prepared as follows: the frozen silkworm pupae are washed with clean water; the washed silkworm pupae are put into boiling water and boiled for 5 minutes, and then taken out and cooled; the silkworm pupae are spread on clean gauze and the water is drained; the oven temperature is controlled at 60-70°C, and the silkworm pupae are dried at low temperature for 8-10 hours, during which the silkworm pupae are turned over 2-3 times, until the silkworm pupae are completely dry; the dried silkworm pupae are put into a grinder and ground into a coarse powder state.

[0018] Furthermore, the hair shrimp powder is prepared according to the following method: fresh hair shrimps are selected, washed with clean water to remove impurities; the washed hair shrimps are steamed in a pot for 3-5 minutes; the steamed hair shrimps are spread out and naturally dried for 1-2 days until the hair shrimps are completely dry; the dried hair shrimps are put into a grinder and ground into fine powder; the earthworm powder is prepared according to the following method: fresh earthworms are selected, washed with clean water for multiple times until the water becomes clear, and dirt and fishy smell on the body surface are removed; the cleaned earthworms are put into boiling water for blanching for 1 minute, and after being taken out, they are quickly put into ice water for cooling; the cooled earthworms are placed on a clean gauze and the water is thoroughly drained; the drained earthworms are evenly spread on a drying rack or a baking tray, the temperature is controlled at 50-60°C, and they are slowly baked at low temperature for 6-8 hours, and the dried earthworms are put into a grinder and ground into a coarse powder state.

[0019] Furthermore, the wheat germ powder is prepared according to the following method: selecting high-quality wheat grains, repeatedly washing to remove impurities, and thoroughly draining the water; putting the wheat grains into a grinding machine, lightly rolling to remove the outer shell (bran) and part of the endosperm, and using a screening device to separate the wheat germ; after the wheat germs are spread out, they are put into an oven, the temperature is controlled at about 130° C., and low-temperature baking is performed for 15-20 minutes, during which the wheat germs are turned over twice, and baked until they are slightly yellow and emit a wheat aroma; after the baked wheat germs are cooled, they are put into a grinder, and ground. Grind into powder; the flaky algae powder is made as follows: soak fresh seaweed in fresh water to remove surface mud and salt, and finally rinse thoroughly with running water; blanch the cleaned seaweed in boiling water for 3-5 minutes and then take it out; put the seaweed into a blender or a grinder to make coarse particles (it does not need to be completely ground into powder); spread the prepared algae mud on a bamboo curtain and flatten it with a rolling pin to a thickness of about 1-2 mm; put the algae flakes in the sun to dry naturally (1-2 days) to obtain flaky algae powder.

[0020] Further, the snowflake powder is made as follows: Wash the potatoes, peel and slice them, and soak them in clean water; Put the soaked potato slices into a steamer and steam them over high heat for 15 - 20 minutes until they are completely cooked and in a semi - transparent state; Spread the steamed potato slices on baking paper and gently flatten them with a rolling pin to form thin flakes (do not press too tightly), with the thickness controlled at 1 - 2 mm; Spread the flattened potato slices in a well - ventilated place and let them dry naturally for 1 - 2 days until completely dry; Grind the dried potato slices into large pieces with a crusher; Put the large - piece potato powder into a sealed bag and freeze it in the freezer for 30 minutes, then take it out and knead it again to disperse, forming fluffy and loose snowflake powder.

[0021] Further, the vital gluten is made as follows: Mix high - gluten flour and clear water and stir well to knead into a relatively firm and smooth dough, cover it with a wet cloth and let it stand for 30 minutes; Put the rested dough into a large basin filled with cold water and knead the dough by hand, adding water and kneading repeatedly until the water becomes clear, and the remaining part is the gluten mass; Place the washed gluten mass on a gauze and let it drain naturally for 30 minutes; Tear the gluten mass into small pieces and let it dry naturally for 1 - 2 days; Put the dried gluten into a crusher and grind it into fine powder, then sieve it 1 - 2 times to ensure that the powder is uniform and there are no large particles. The vanillin (food additive) is purchased from Shanghai Xinhua Spice Co., Ltd.

[0022] Further, the rope in step S4 is a nylon rope or a hemp rope.

[0023] Compared with the existing technology, the technical solution of the present invention has the following beneficial effects:

[0024] Firstly, the present invention has developed a brand - new trapping bait formula; secondly, it has designed a new type of cage net. In terms of the trapping bait formula, compared with the method of Yu Guilan et al. (2024), the present invention has improved the raw material ratio of the trapping bait for Tilapia zillii, increased the proportion of animal - sourced protein, and significantly reduced the amount used each time. At the same time, the present invention improves the fish - attracting effect by adding an attractant (vanillin) to the trapping bait. In terms of the design of the new type of cage net, the present invention has made an anti - escape design for the fish - inlet, selected a suitable position to fix the bait bag, expanded the space of the tail fish - gathering area, and significantly improved the trapping efficiency.

[0025] To verify the trapping effects of the trapping bait (containing attractant) and the cage net, the present invention selects a certain Shuikou Reservoir reservoir area, which is a key area for the invasion of Tilapia zillii, as the trapping test area, and conducts centralized trapping on juvenile Tilapia zillii, achieving good trapping effects. Practice has proved that the technical solution of the present invention is an environmentally friendly and economically efficient trapping method, which can efficiently trap juvenile Tilapia zillii, specifically manifested in the following aspects:

[0026] In terms of the trapping method:

[0027] (1) Fix the bait bag near the fish inlet, which can hold the trapping bait and improve the trapping efficiency;

[0028] (2) A concrete counterweight is fixed at the end of the tail of the trapping device to ensure that the trapping device can be fully deployed and remain stable underwater, is not easily overturned by the water flow, and enhances the underwater applicability of the trapping device;

[0029] (3) The funnel end of the fish inlet adopts a circular frame and is equipped with flexible plastic sheets. Fish can easily push open the plastic sheets from the outside and enter. After entering, the plastic sheets automatically close, effectively preventing fish from escaping;

[0030] (4) The space of the fish collection area at the tail is increased, which can accommodate more catches and improve the trapping efficiency of the trapping device.

[0031] In terms of the trapping device:

[0032] Ordinary trapping devices generally do not place bait or use general bait pellets during use, and often require a longer time to gather fish. The trapping cycle is long and the catches are not specific. Therefore, the present invention designs a trapping bait according to the feeding characteristics of Oreochromis niloticus. This bait has the following advantages:

[0033] (a) The usage amount is small. Only 100 g at least each time is required for trapping, which is economical and efficient;

[0034] (b) It is more convenient, can be directly put into use, and the operation is simple;

[0035] (c) It has strong pertinence. Oreochromis niloticus is the absolute dominant species in each trapping catch.

[0036] In terms of the trapping bait:

[0037] The present invention increases the proportion of attractant components and animal-derived proteins, which is close to the food composition of wild Oreochromis niloticus; and adds 2% vanillin to provide a milk fragrance for the bait, making the fragrance of the bait spread better in water and enhancing the fish-attracting effect. The present invention adds 5% gluten powder and 12% wheat germ powder to the bait, both of which have viscosity and can keep the bait mass in a state underwater for 1-2 days; and through the combined action of wheat germ powder and snow powder, an atomization circle is formed around the bait, having a continuous fish-attracting effect. Brief Description of the Drawings

[0038] Figure 1 It is a schematic diagram of the overall appearance structure of the trapping device cage in the present invention.

[0039] Figure 2 It is a schematic diagram of the trapping location in an embodiment of the present invention.

[0040] In the figure: 1. Juvenile fish trapping area; 2. Juvenile fish aggregation area; 3. Bait bag; 4. Funnel-shaped internal connection channel; 5. Circular frame at the end of the fish inlet; 6. Flexible plastic sheet; 7. Lead block at the fish inlet; 8. Funnel-shaped juvenile fish inlet; 9. Circular frame; 10. Concrete counterweight block. Detailed implementation method

[0041] The following is a detailed description of the embodiments of the present invention in conjunction with the accompanying drawings: These embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operation processes are given, but the protection scope of the present invention is not limited to the following embodiments.

[0042] Embodiment:

[0043] I. Trapping location and time:

[0044] As Figure 2 shown, after obtaining permission from the local fishery department, from December 6th to December 11th, 2024, two trapping points (two points in the figure) were set in the shallow water area (water depth 0.5m - 2m), gentle slope (slope less than 45°), and well-lit area with sandy and muddy bottom in the Shuikou Reservoir area of Zhanghu Town, Yanping District, Nanping City, Fujian Province to trap the wild population of Oreochromis niloticus.

[0045] II. Investigation of the background fish resources at the trapping location:

[0046] Before trapping, three-layer drift nets were set in the waters near the trapping points to investigate the background fish resources.

[0047] III. Installation of trapping nets:

[0048] The juvenile Oreochromis niloticus live in the shallow water area near the reservoir shore, and after growing to a slightly larger size, they live in the middle and upper water layers of the reservoir. The length of the long cage is generally 2m - 6m, which can cover the area where the juvenile Oreochromis niloticus live and can trap most of the juveniles in this water layer.

[0049] As Figure 1 shown, it includes a juvenile fish trapping area 1 and a juvenile fish aggregation area 2. The juvenile fish trapping area 1 and the juvenile fish aggregation area 2 are connected by a funnel-shaped internal connection channel 4. The juvenile fish trapping area 1 includes a funnel-shaped juvenile fish inlet 8, a lead block 7 at the fish inlet, a circular frame 5 at the end of the fish inlet, a flexible plastic sheet 6, and a bait bag 3. The lead block 7 at the fish inlet is sewn on the nylon net below the juvenile fish inlet, the circular frame 5 at the end of the fish inlet is sewn at the end of the juvenile fish inlet, the flexible plastic sheet 6 is perforated and fixed to the circular frame 5 at the end of the fish inlet by cable ties, the bait bag 3 is fixed to the nylon net by its own binding rope, each section of the cage is connected by the funnel-shaped internal connection channel 4, the last section of the juvenile fish aggregation area uses an enlarged circular frame, and a concrete counterweight block 10 is installed in the net bag inside the end of the trapping device.

[0050] The specifications of the fishing cage are 25 cm × 25 cm × 5 m. The 25-cm fishing cage frame can provide sufficient trapping space. The frame is made of stainless steel wire to ensure stability and corrosion resistance during long-term use in water. The net surface material is nylon, and the mesh size is 4 mm (the body lengths of the trapped juvenile fish are concentrated in the range of 1.0 cm to 5.0 cm, and the 4-mm mesh is not likely to cause them to escape). A counterweight is fixed on the lower side of the fish inlet. The fish inlet is designed as a funnel-shaped one-way inlet that slopes downward, with a width of 10 cm. A flexible plastic sheet is installed at the end of the inlet, making it difficult for the juvenile fish to escape once they enter the fishing cage. The internal connection of the fishing cage uses a funnel-shaped structure that is wider at the top and narrower at the bottom, causing the fish to swim deeper into the fishing cage after entering. A detachable bait bag (the net bag is made of nylon, with a mesh of 2.5 mm and a specification of 15 cm × 10 cm) is set in the middle of the fishing cage, near the inlet of the fishing cage. The last section of the fishing cage is made into a cylindrical shape using a circular frame to increase the fish collection space and improve the trapping efficiency; the tail gradually tapers to facilitate the removal of the catch.

[0051] IV. Trapping bait formula:

[0052] The proportion of each component in the trapping bait is as close as possible to the diet composition of Tilapia zillii under natural conditions. The specific formula is set as follows: silkworm pupa powder 20%, acetes powder 20%, earthworm powder 20%, wheat germ powder 12%, flaky algal powder 11%, snow powder 10%, vital gluten powder 5%, vanillin (purchased from Shanghai Xinhua Spice Co., Ltd.) 2%, and an appropriate amount of clear water.

[0053] The ordinary bait for the control group is the powdered fish bait purchased from a physical fishing gear store.

[0054] V. Preparation of trapping bait:

[0055] Preparation of trapping bait: Mix the acetes powder, earthworm powder, silkworm pupa powder, and flaky algal powder evenly, and stir-fry in a pan until there is a mixed fragrance; after cooling the above raw materials, mix them evenly with wheat germ powder, snow powder, vital gluten powder, and vanillin, pour in an appropriate amount of water, let it stand for 3 min to allow the bait to fully absorb the water, then stir quickly to make the bait form into a ball, and put it into the bait bag.

[0056] Preparation of the control group bait: Add an appropriate amount of clear water to the powdered bait, let it stand for 3 min to allow the bait to fully absorb the water, then stir quickly to make the bait form into a ball, and put it into the bait bag.

[0057] VI. Placement of trapping bait and fishing cage:

[0058] According to the background resource quantity of Oreochromis niloticus in the trapping waters, the dosage of the trapping bait was set at 100 g, and the bait bag was tied to the bait fixing rope inside the fish trap. According to the daily temperature change, the water temperature began to rise around 8:00 am, and Oreochromis niloticus became active and began to feed actively. Therefore, the starting time for placing the fish traps was set at 8:00 am, and the time for retrieving the fish traps was set at 7:00 am the next day. Three fish traps were placed at each trapping point in the experimental waters as the experimental group, and another three fish traps were placed as the control group. The spacing between adjacent fish traps was 10 m. The experiment started at 8:00 am on December 6 and ended at 7:00 am on December 10, lasting for 4 days in total.

[0059] VII. Data Statistics and Analysis:

[0060] During the trapping period, the species composition of the catches in the experimental group and the control group was identified every day, and the body weights of all the catches were measured and recorded. After obtaining the number and body weights of all the juvenile Oreochromis niloticus, data statistical analysis was carried out using Microsoft Excel 2019 and SPSS 27.0.1 software. An independent samples t-test was used for the significance test of differences, and the significance level of the test was set at α = 0.05.

[0061] VIII. Results of the Investigation of Background Fish Resources:

[0062] The results of the investigation of background fish resources are shown in Table 1. A total of 9 species of fish were collected in the Zhanghu section of Shuikou Reservoir, belonging to 9 genera in 3 families of 3 orders. Among them, there were 6 species in Cyprinidae of Cypriniformes, including one species each of genus, Culter, Carassius, Squaliobarbus, Hypophthalmichthys, and Sarcocheilichthys. There were 2 species in Cichlidae of Perciformes, including one species each of Tilapia and Sarotherodon. There was 1 species in Pelteobagrus of Siluriformes. There were two alien fish species, namely Oreochromis niloticus and Oreochromis galilaeus. The statistical results showed (Table 1) that the quantity ratio of Oreochromis niloticus in the Zhanghu section of Shuikou Reservoir was 63.83%, the weight ratio was 54.77%, the abundance was 90 individuals / net, and the resource quantity was 8618.5 g / net.

[0063] Table 1 Results of the Investigation of Background Fish Resources in the Zhanghu Section of Shuikou Reservoir

[0064]

[0065] IX. Analysis of Trapping Effects:

[0066] The trapping results over 4 days showed (Table 2) that the quantity ratio of Oreochromis niloticus in the experimental group [(93.59 ± 2.35)%] was significantly greater than that in the control group [(76.66 ± 6.57)%] (t = -2.425, P = 0.036). At the same time, the abundance of Oreochromis niloticus in the experimental group [(64.67 ± 12.05) fish / net] was also significantly greater than that in the control group [(22.55 ± 5.60) fish / net] (t = -3.168, P = 0.006). The results indicated that the trapping effect of the trapping bait for Oreochromis niloticus (containing attractants) was significantly better than that of the control group bait.

[0067] Table 2 Trapping results of two kinds of baits

[0068]

[0069] The trapping bait in this embodiment has good specificity for Oreochromis niloticus, and the attracting effect on other fish is significantly weaker than that on Oreochromis niloticus. The trapping results showed that the average quantity ratio per cage was (93.59 ± 2.35)%, which was greater than the average quantity ratio per cage (85.38%) in the prior art. The average abundance in this embodiment was (64.67 ± 12.05) fish / net, which was less than the average abundance (124 fish / net) of the application No. CN118489641A. This might be caused by different trapping seasons. This experiment was conducted in December, and the water temperature was relatively low (17 - 19°C), not during the breeding period of Oreochromis niloticus in Shuikou Reservoir, so the number of juvenile fish was less. The trapping bait and trapping cage in this embodiment can obtain better trapping effects in shallow waters (water depth 0.5 - 2 m) with sandy and muddy bottom, gentle slopes (slope less than 45°), water temperature above 20°C, and sufficient light, and preferably far away from human noise. The cage designed for juvenile fish in the present invention has the advantages of strong underwater stability, anti - escape, high capture efficiency, and strong fish - attracting specificity.

[0070] The device and method for trapping juvenile Oreochromis niloticus in the present invention are also suitable for fry of Oreochromis.

[0071] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above - mentioned embodiments. What is described in the above - mentioned embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A device for trapping juvenile Tilapia chinensis, characterized in that: A juvenile fish trapping area (1) and a juvenile fish gathering area (2) are connected via a funnel-shaped internal connection channel (4). The juvenile fish trapping area (1) comprises a funnel-shaped juvenile fish inlet (8), a fish inlet lead block (7), a circular frame at the end of the fish inlet (5), a flexible plastic sheet (6) and a bait bag (3). The fish inlet lead block (7) is sewn on a nylon net below the juvenile fish inlet. The circular frame at the end of the fish inlet (5) is sewn on the end of the juvenile fish inlet. Holes are punched in the flexible plastic sheet (6) and the flexible plastic sheet is fixed to the circular frame at the end of the fish inlet (5) via a cable tie. The bait bag (3) is fixed to the nylon net via a self-contained binding rope. Each section of the ground cage is connected via a funnel-shaped internal connection channel (4). The last section of the juvenile fish gathering area uses an enlarged circular frame. A concrete counterweight (10) is installed in the mesh bag inside the tail end of the trapping device.

2. A device for trapping juvenile Tilapia zeae according to claim 1, characterized in that: The frame is made of stainless steel; the mesh is made of nylon or polyethylene; the bait bag is a rectangular nylon mesh bag with a mesh size of 2.5 mm and a size of 15 cm × 10 cm; the front and middle parts of the frame are square, and the tail is round.

3. A method for trapping juvenile Tilapia chinensis, characterized in that: The specific steps include the following: S1. Select the trapping location and time: select shallow water areas with sand and silt bottom, gentle slopes, and places with sufficient light to set up trapping points; according to the change of water temperature during the day, the water temperature begins to rise around 8:00 am, and the juvenile tilapia becomes active and starts to actively feed, so the starting time of placing the trapping device is set to 8:00 am, and the time of retrieving the trapping device depends on the season. In the breeding season of tilapia, the harvesting time is set to 20:00 on the same day; in the non-breeding season of tilapia, the harvesting time is set to 8:00 am the next day; S2. Make bait for trapping: mix shrimp powder, earthworm powder, silkworm pupa powder and flaky algae powder evenly, and fry them in a pan until there is a mixed aroma; after cooling the above raw materials, mix them evenly with wheat germ powder, snowflake powder, gluten powder and vanillin, pour in appropriate amount of water, let stand for 3 minutes to wait for the bait to fully absorb water, then stir quickly to make the bait clumping, and put it into the bait bag; S3. Place bait: Determine the amount of bait according to the background resources of Tilapia in the trapping waters, and tie the bait bag containing the bait to the bait bag fixing rope in the trapping device; S4. Place the trapping device: Fix one end of the trapping device to the shore with a rope, which is a nylon rope or a hemp rope, and place the other end into the waters for trapping juvenile Tilapia chinensis. Each trapping device should be placed 10m apart. S5. Harvest: Quickly lift the trap out of the water, untie the knot at the tail, and pour out the fry of Tilapia chinensis from the tail of the trap.

4. A method for trapping juvenile Tilapia zeae according to claim 3, characterized in that: The formula of the trapping bait in the steps S2 and S3 comprises the following components: silkworm pupa powder, hair shrimp powder, earthworm powder, wheat germ powder, flaky algae powder, snowflake powder, gluten powder, and vanillin; the contents of the above components are respectively 20% by mass: 20% silkworm pupa powder, 20% hair shrimp powder, 20% earthworm powder, 12% wheat germ powder, 11% flaky algae powder, 10% snowflake powder, 5% gluten powder, and 2% vanillin; the hair shrimp powder, earthworm powder, silkworm pupa powder, and flaky algae powder are evenly mixed, fried in a pan until a mixed aroma is obtained, then cooled and evenly mixed with wheat germ powder, snowflake powder, gluten powder, and vanillin, an appropriate amount of water is poured in, and the bait is allowed to stand for 3 minutes to wait for the bait to fully absorb water, and then quickly stirred to make the bait into a ball. When in use, the bait ball is first put into a bait bag, and then the bait bag is hung in a trapping device to trap young Tilapia.

5. A method for trapping juvenile Tilapia zeae according to claim 4, characterized in that: The silkworm pupa powder is prepared as follows: washing frozen silkworm pupae with clean water; boiling the washed silkworm pupae in boiling water for 5 minutes, taking them out and cooling them; spreading the silkworm pupae on clean gauze and draining the water; controlling the oven temperature at 60-70°C and drying at low temperature for 8-10 hours, turning them over 2-3 times during the drying process, until the silkworm pupae are completely dry; and putting the dried silkworm pupae into a grinder and beating them into a coarse powder state.

6. A method for trapping juvenile Tilapia zeae according to claim 4, characterized in that: The hair shrimp powder is prepared as follows: fresh hair shrimps are selected, washed with clean water to remove impurities; the washed hair shrimps are steamed for 3-5 minutes; the steamed hair shrimps are spread out and naturally dried for 1-2 days until the hair shrimps are completely dry; the dried hair shrimps are put into a grinder and ground into fine powder; the earthworm powder is prepared as follows: fresh earthworms are selected, washed with clean water for multiple times until the water becomes clear, and dirt and fishy smell on the body surface are removed; the cleaned earthworms are put into boiling water for blanching for 1 minute, and after being taken out, they are quickly put into ice water for cooling; the cooled earthworms are placed on a clean gauze and the water is thoroughly drained; the drained earthworms are evenly spread out on a drying rack or a baking tray, the temperature is controlled at 50-60°C, and they are slowly baked at low temperature for 6-8 hours, and the dried earthworms are put into a grinder and ground into a coarse powder state.

7. A method for trapping juvenile Tilapia zeae according to claim 4, characterized in that: The wheat germ powder is prepared as follows: select high-quality wheat grains, wash them repeatedly to remove impurities, and drain them thoroughly; put the wheat grains into a grinding machine, gently crush them to remove the shell and part of the endosperm, and use screening equipment to separate the wheat germ; spread the wheat germs flat, put them into an oven, control the temperature at about 130°C, and bake them at a low temperature for 15-20 minutes, turning them twice during the process, and bake them until they are slightly yellow and emit a wheat aroma; after the baked wheat germs are cooled, put them into a grinder and grind them into powder; the flaky algae powder is prepared as follows: soak fresh seaweed in fresh water to remove surface mud and salt, and finally rinse them thoroughly with running water; blanch the washed seaweed in boiling water for 3-5 minutes and then take them out; put the seaweed into a blender or a grinder and beat them into coarse particles; spread the prepared algae mud on a bamboo curtain and flatten it with a rolling pin to a thickness of about 1-2 mm; put the algae flakes in the sun to dry naturally to obtain flaky algae powder.

8. A method for trapping juvenile Tilapia zeae according to claim 4, characterized in that: The snowflake powder is prepared as follows: washing potatoes, peeling and slicing them, and soaking them in clean water; putting the soaked potato slices into a steamer, steaming them over high heat for 15-20 minutes, until they are fully cooked and translucent; spreading the steamed potato slices on baking paper, and gently flattening them with a rolling pin to form thin slices with a thickness of 1-2 mm; spreading the pressed potato slices in a well-ventilated place, and drying them naturally for 1-2 days until they are completely dry; using a crusher to beat the dried potato slices into large pieces; putting the large potato slice powder into a sealed bag, freezing it in a freezer for 30 minutes, and taking it out and kneading it again to form fluffy and loose snowflake powder.

9. A method for trapping juvenile Tilapia zeae according to claim 4, characterized in that: The gluten powder is prepared as follows: high-gluten flour and clean water are mixed and stirred, kneaded into a hard and smooth dough, covered with a wet cloth, and left to stand for 30 minutes; the rested dough is placed in a large basin filled with cold water, kneaded by hand, and repeatedly added with water and kneaded until the water becomes clear, and the remaining part is the gluten dough; the washed gluten dough is placed on gauze and drained naturally for 30 minutes; the gluten dough is torn into small pieces and dried naturally for 1-2 days; the dried gluten is placed in a grinder, ground into fine powder and sieved 1-2 times to ensure uniform powder quality without large particles. The vanillin is purchased from Shanghai Xinhua Spice Co., Ltd.

10. A method for trapping juvenile Tilapia chinensis, characterized in that: When implementing the operation steps, the device for catching young Tilapia zebulii in claim 1 is used.

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