Biological prevention and control method for typical fouling organisms in southern mariculture net cage and application of biological prevention and control method

Abstract

The invention provides a biological prevention and control method for typical fouling organisms in a southern mariculture net cage and application of the biological prevention and control method. The main idea is as follows: firstly, finding out community composition and space-time change rules of fouling organisms in a sea area, secondly, investigating main fishes in the sea area, determining bait organism composition of the main fishes, selecting fingerlings which can ingest target fouling organisms and meet cage culture conditions, and finally, carrying out culture tests. The biological control effect of the fishes on the target fouling organisms is verified. The invention further provides a method for clearing away the sea squirts attached to the southern mariculture net cage by using the feeding habit of the siganus giganteus, the problem that a large amount of manpower and material resources are consumed in a traditional sea squirt clearing technology is effectively solved, and culture environment damage caused in the traditional sea squirt clearing process is reduced; and the influence on the cultured object in the netting replacement process is reduced, so that the economic loss in the culture period is reduced. A foundation is laid for establishing a biological prevention and control sea squirt model, and the method has a very good application value in natural seawater cage culture.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of biocontrol of fouling organisms in net cages, and relates to a biocontrol method for typical fouling organisms in net cages for seawater aquaculture in the south, in particular to a biocontrol method for sea squirts, a typical fouling organism in net cages for seawater aquaculture in the south, by using Siganus oramin. BACKGROUND

[0002] In net cage aquaculture in the south, the large amount of fouling organisms on the net cover in the high-temperature season is one of the main problems that trouble most practitioners. Fouling organisms refer to microorganisms, plants and animals that adhere to the surface of underwater facilities. The continuous growth and reproduction of fouling organisms can cause damage to the facilities or affect their performance. Marine fouling organisms not only seriously affect the health and stability of the marine ecosystem, but also cause huge economic losses to the aquaculture industry, the shipping industry and marine engineering facilities.

[0003] In the aquaculture industry, fouling organisms will compete with the cultured objects for living space and nutrients, resulting in a decrease in production. In addition, the large amount of fouling organisms leads to an increase in the self-weight of the net cage and a decrease in the buoyancy, causing the net rope to bear more weight and shortening the service life of the net cage. Moreover, during the peak period of biological mass in summer, the fouling organisms will cause the mesh of the net cage to be blocked, hindering the exchange of water between the inside and outside of the net cage and affecting the growth of the cultured objects, and even causing death.

[0004] Sea squirts are one of the most typical marine fouling organisms, belonging to the Chordata Urochordata. Their life history mainly includes two stages: swimming larvae and sessile adults. Adults often attach to various substrates in the sea to live a sessile life. In addition to natural substrates such as rocks and algae, artificial facilities such as ship hulls, piers and net cages are also their main habitats. A large amount of sea squirts will compete with the cultured objects for oxygen and nutrients, resulting in a decrease in production and causing serious negative impacts on aquaculture. On net cages for seawater aquaculture in the south, the biomass of sea squirts accounts for more than 80% of the total amount of fouling organisms in summer. High-density sea squirts attached to the net cage and rope are difficult to remove. Currently, the main method for removal is sun exposure, which is time-consuming and labor-intensive and causes mechanical damage to the net to some extent. Therefore, it is of positive significance to seek a reasonable method for preventing and controlling attached sea squirts for the net cage aquaculture industry in the south. SUMMARY

[0005] The present application is aimed at the above challenges. To solve the above problems, the main purpose of the present application is to propose a biocontrol method for typical fouling organisms in net cages for seawater aquaculture in the south and its application, in particular to propose a biocontrol method for preventing and controlling attached sea squirts in net cages by using fish feeding.

[0006] The general idea of the present application is to first identify the community composition and spatio-temporal variation of fouling organisms in the sea area, secondly investigate the main fish species in the sea area and determine their prey composition, select fish species that can feed on target fouling organisms (sea squirts) and meet the conditions of net cage culture, and finally carry out culture test to verify the biological control effect of fish on target fouling organisms (sea squirts).

[0007] In the first aspect of the present application, a general idea method for biological control of typical fouling organisms in southern marine net cages is provided, comprising the following steps:

[0008] (1) Identify the community composition and spatio-temporal variation of fouling organisms in the sea area:

[0009] According to "Marine Survey Specification Part 6: Marine Biological Survey", the fouling organisms attached to the net cage in the culture sea area are investigated by hanging net test. The main species and community structure of the fouling organisms on the net cage are understood, and the fouling organisms are sampled and analyzed to determine the species and calculate the attachment area of each type of fouling organisms.

[0010] Specifically, a certain size of net is used for hanging net test, and the underwater duration of the hanging net is 1-5 months. Different groups of nets are set at different depths; the net body is perpendicular to the seabed, the main species and community structure of the fouling organisms on the net cage are determined, the fouling organisms on the net are sampled and analyzed to determine the attachment area of each type of fouling organisms.

[0011] (2) Investigate the main fish species in the sea area and determine their prey composition

[0012] The main fish species in the southern sea area are collected, and the stomach contents of the main fish species are extracted on site according to the "Marine Survey Specification". The stomach contents are frozen and stored in the laboratory. The prey composition of the main fish species in the investigation sea area is identified by using 18S rDNA high-throughput sequencing technology. By analyzing the stomach content composition of representative fish species in the culture sea area, fish species that mainly feed on target fouling organisms are selected, and fish species that are the object of biological control are determined.

[0013] Specifically, high-throughput sequencing technology is used to analyze the stomach contents of fish species that mainly feed on target fouling organisms, and the relative abundance of OTUs at the door classification level is calculated. At the same time, OTUs with high relative abundance are selected and compared with the GenBank database to explore their similar species information. Further, OTU sequences belonging to fouling organisms are selected, and a phylogenetic tree is constructed. Finally, combined with the OTU relative abundance data of the target fouling organisms, the feeding differences of representative fish species in the test area on the target fouling organisms are analyzed, and the biological control object is determined.

[0014] (3) Put the biological control object determined in step (2) into the test net cage, set different breeding density gradients, record the change of the target fouling organism attachment area through underwater photography technology, combine image analysis to calculate the weight change amount and the feeding efficiency, and at the same time, based on the weight change amount of the target fouling organism AWtarget fouling organism, the total weight of the biological control object Wbiological control object and the feeding time t, a regression equation is established to predict the reduction amount of the target fouling organism, so as to guide the prevention and control density configuration and the throwing strategy.

[0015] Specifically, the net photos of the fouling organisms attached by the underwater camera are imported into the image processing software Image J, a scale is established according to the size of the net, the fouling organisms on the photographed photos are circled by using the irregular image selection function in the software, and the attachment area of the target fouling organisms on each surface of the net cage is calculated; then the corresponding weight of the target fouling organisms is calculated according to the regression equation of the attachment area and the weight of the target fouling organisms, the weight change of the target fouling organisms in the net cages with different breeding densities is statistically analyzed, and the weight change rate and the feeding efficiency of the biological control object on the target fouling organisms are calculated.

[0016] Further, the feeding efficiency formula is as follows: FR=[C1×(1+K)-C2] / (w×t),

[0017] In the formula, FR: daily feeding efficiency; C1: initial weight; C2: final weight; K: loss rate; w: weight of the biological control object; and t: time, unit: day;

[0018] The regression equation is as follows: AW 目标污损生物 = -A+ B× t + D × W 生物防治对象 ,

[0019] In the formula, AW 目标污损生物 : reduction weight of the target fouling organisms, unit: gram; t: day; W 生物防治对象 : total weight of the biological control object, unit: gram; A is a constant, and B and D are coefficients.

[0020] In the application, the key target fouling organism is sea squirts, and the biological control method for the sea squirts is described.

[0021] In the second aspect of the application, a biological control method for the typical fouling organism sea squirts of the southern seawater breeding net cage by using Siganus canaliculatus is provided, which comprises the following steps:

[0022] (1) Find out the community composition and the spatiotemporal variation law of the fouling organisms in the sea area

[0023] The fouling organisms attached on the breeding net cage in the sea area are investigated by using the hanging net test. The main species and the community structure of the fouling organisms on the net cage are understood, the fouling organisms are sampled and analyzed, the species are determined, and the attachment area of each type of fouling organisms is calculated.

[0024] (2) Investigate the main fish species in the sea area and determine their prey composition

[0025] Collect the main fish species in the South China Sea area, extract the stomach contents of the main fish species on site according to the "Marine Survey Specification", and freeze them for laboratory storage. Use 18S rDNA high-throughput sequencing technology to identify the prey composition of the main fish species in the survey sea area.

[0026] The main fish species in the South China Sea area are: Siganus canaliculatus (Lacepède, 1804) Siganus canaliculatus ), Pseudosciaena crocea (Richardson, 1846) Larimichthys crocea ), Serrulina fusimaculata (Oshima, 1927) Collichthys lucidus ), Upeneus vittatus (Day, 1871) Chrysochir aureus Acanthopagrus latus ), Sparus aurata (Linnaeus, 1758) Saurida elongata ), Saurida elongata (Richardson, 1848) Pampus argenteus ), Selaroides leptolepis (Bleeker, 1852) Lepidotrigla microptera Setipinna taty ), Siganus canaliculatus (Lacepède, 1804) Takifugu flavidus ), Setipinna taty (Valenciennes, 1837) Takifugu alboplumbeus ), Takifugu nigrimarginatus (Oshima, 1927) Lagocephalu wheeler ), Takifugu obscurus (Temminck et Schlegel, 1846) Stephanolepis cirrhifer ), Lagocephalus sceleratus (Gmelin, 1789) Siganus canaliculatus ), Lagocephalus suezensis (Oshima, 1927) Figure 1 ), and 13 other main fish species.

[0027] Using 18S rDNA V4 region universal primers, the Illumina Miseq high-throughput sequencing technology method was used to compare and analyze the differences in the prey food composition of 13 fish species, to select target fish species for subsequent biological control of fouling organisms using the downlink effect of the food chain; according to the prey composition of the main fish species, the relative content of each type of fouling organism in the stomach contents was compared and analyzed, especially the feeding situation of sea squirts, to determine Siganus canaliculatus as the subsequent verification fish.

[0028] (3) Conduct a cultivation test to verify the biological control effect of fish on sea squirts

[0029] Based on step (2), the fish used for the cultivation test was determined to be Siganus canaliculatus. Five groups of Siganus canaliculatus with different cultivation densities were placed in the test net cage, and an underwater camera was used to shoot the attachment area of each type of fouling organism on the net cage, and the attachment area change of each type of fouling organism, especially sea squirts, was calculated. At the same time, based on the weight change amount (ΔW 海鞘 ), the total weight of fish (W 鱼total ) and the feeding time (t), a regression equation was established to predict the amount of sea squirts reduced, guide the prevention and control density configuration and fish release strategy.

[0030] Among them, the experimental fish used in the breeding experiment were all long-fin basket fish with strong physique and uniform size, with a body length of (202±13) mm and a weight of (109±22) g.

[0031] During the experiment, the breeding experiment set up five groups of breeding densities according to the optimal breeding density of longfin basket fish for single breeding and mixed breeding, namely 0 fish / cubic meter, 5 fish / cubic meter, 10 fish / cubic meter, 20 fish / cubic meter, and 40 fish / cubic meter. The results showed that the breeding densities of 5 fish / cubic meter and 10 fish / cubic meter were better. Among them, the longfin basket fish in the 5 fish / cubic meter group showed higher stability and persistence in feeding behavior, and had better tunicate prevention and control effect, which was a more ideal ecological prevention density configuration under the conditions of this experiment.

[0032] Furthermore, during the aquaculture experiment, underwater cameras were used to record the changes in the attachment area of ​​​​scabbards on the aquaculture cages in the sea area through fixed video recording and panoramic photography. The recording and image processing frequency was once a day.

[0033] The regression equation established based on the experiment is as follows: ΔW 海鞘 = −36.48 + 16.36 × t + 0.02667 ×W 鱼total , where, ΔW 海鞘 : weight loss of ascidian, in grams; t: days; W: 鱼Total Total weight of longfin basket fish in grams. This prediction model allows precise setting of fish stocking weight and timing in actual production, improving efficiency and saving costs. The model predicts optimal fish stocking weights and avoids resource waste.

[0034] The third aspect of the present invention provides the use of basket fish in removing ascidians attached to seawater aquaculture cages. The biological control of ascidians is achieved by co-culturing basket fish in the seawater aquaculture cages, and the breeding density is preferably 5 fish / cubic meter.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] The present invention provides a method of utilizing long-fin basket fish ( Figure 2The method can remove the sea squirts attached to the net cage of the southern seawater culture, avoid the net cage blockage, increase the water permeability, maintain the culture environment and reduce the disease occurrence of the cultured fish in the net cage. The sea squirts attached to the net cage of different culture densities of the longfin yellowtail in the culture period of 7 days are removed completely. The traditional method for removing the sea squirts attached to the net cage of the seawater culture mainly relies on the replacement of the whole net cage, and the replaced net cage is dried and cleaned manually, so that the prevention and treatment effect is achieved. The method can effectively solve the problem of the large consumption of manpower and material resources in the traditional sea squirt removal technology, reduce the damage of the culture environment in the traditional sea squirt removal process and the influence on the cultured objects in the replacement process of the net cage, and further reduce the economic loss in the culture period.

[0037] The optimal culture density of the longfin yellowtail for removing the sea squirts. Five groups of culture densities (0 tail / cubic meter, 5 tail / cubic meter, 10 tail / cubic meter, 20 tail / cubic meter and 40 tail / cubic meter) are designed in the test process of the application, the change of the sea squirts in the five groups of culture densities is shot every day, the change amount of the attached area, the weight change amount and the change rate of the sea squirts in different culture densities are calculated, and finally the optimal culture density is obtained. The culture density and size of the longfin yellowtail required in the culture period can be determined according to the estimated attached area of the sea squirts in the net cage and the size of the culture water. The method for preventing and treating the sea squirts by using the longfin yellowtail is simple and convenient, the prevention and treatment effect of the longfin yellowtail on the sea squirts under different culture densities can be evaluated in a short time, the method lays a foundation for establishing the biological prevention and treatment model of the sea squirts, has a positive promoting effect on controlling the overall economic cost and realizing the green prevention and treatment, and has a good application value in the natural seawater net cage culture. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 3 The figure shows the net cage frame of the embodiment of the application.

[0039] Siganus canaliculatus The figure shows the weight change of the attached sea squirts.

[0040] Larimichthys crocea The figure shows the change of the feeding efficiency of the sea squirts. DETAILED DESCRIPTION

[0041] The following examples and experimental examples further illustrate the application and are not to be understood as limiting the application. The examples do not include a detailed description of the conventional methods, which are well known to a person with ordinary skill in the art and are described in many publications.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Methods and materials similar or equivalent to those described herein can be used in the practice of the present application. The preferred materials and methods are described herein.

[0043] The experimental methods in the following examples, unless otherwise specified, are generally carried out according to the conventional conditions, or according to the conditions recommended by the manufacturer.

[0044] The present embodiment provides a method for preventing and treating sea squirts in a net cage for southern marine aquaculture by using long-fin rabbitfish, and the steps are as follows:

[0045] Step 1, determining the attached species, quantity, and community change of fouling organisms in the southern marine aquaculture area

[0046] The hanging net experiment is used to investigate the fouling organisms in the sea area, and all operations are carried out in accordance with the relevant provisions of "Marine Investigation Standard Part 6: Marine Biological Investigation" (GB / T 12763.6-2007). The hanging net experiment is carried out using a polyethylene (PE) mesh with a size of 50 cm x 50 cm. The underwater duration of the hanging net is 1, 2, 3, 4, and 5 months, respectively. The surface layer is 0.5 meters from the water surface, and the bottom layer is 6 meters from the water surface. Each group of mesh is divided into 4 depths (0.5-1.5 meters, 2-3 meters, 3.5-4.5 meters, and 5-6 meters), and a total of 2 parallel groups are set up, totaling 80 mesh samples. The top of the mesh is fixed to the floating row of the culture platform, and the bottom is bound with a weight, so that the mesh body is perpendicular to the seabed. The fouling organisms on the mesh are sampled and analyzed to determine the attached area of various types of fouling organisms.

[0047] Step 2, determining the target fish species that feed on sea squirts

[0048] The high-throughput sequencing technology is used to analyze the representative fish species in the southern sea area, including long-fin rabbitfish ( Collichthys lucidus Chrysochir aureus ), large yellow croaker ( Acanthopagrus latus ), spiny-headed mei-tong fish ( Saurida elongata ), sharp-headed yellow-fin threadfin ( Pampus argenteus ), yellow-fin puffer ( Lepidotrigla microptera ), long eel ( Setipinna taty Takifugu flavidus ), silver pomfret ( Takifugu alboplumbeus ), long-fin red-niece fish ( Lagocephalu wheeler ), yellow carp ( Stephanolepis cirrhifer ), chrysanthemum yellow oriental tilefish ( Figure 1 ), lead point oriental tilefish ( Figure 2 Figure 3 ), light fin rabbit head puffer ( ​ i), silk back fine scale puffer ( ​ ​). The obtained data were statistically analyzed, and the relative abundance of OTUs at the phylum classification level was calculated using Excel. Meanwhile, OTUs with high relative abundance were selected and compared with the GenBank database using BLAST (Basic Local Alignment Search Tool) to explore their similar species information. Further, OTU sequences belonging to fouling organisms were screened, and a phylogenetic tree was constructed using the Neighbor-Joining (NJ) method with MEGA 11 software. Finally, the relative abundance data of OTUs of sea squirts were combined to analyze the differences in predation of sea squirts by representative fish in the test area.

[0049] Step 3, carry out cultivation test to verify the biological control effect of fish on sea squirts, as follows:

[0050] (1) Net production

[0051] First, make the net: the test net is woven from polyethylene material with a mesh size of 30 mm, and the net frame is spliced from PVC pipes with a diameter of 2 cm. The overall net frame specification is 50 cm x 50 cm, and the number of net pieces is 80. Then place the net pieces; the prepared net pieces are threaded with nylon ropes with a diameter of 1 cm and hung vertically in the test sea area for 2 months to wait for the attachment of fouling organisms. Produce the net frame: the seawater aquaculture net frame specification is 1 m x 1 m x 1 m, and the frame material is PVC plastic pipe with a diameter of 2 cm. Cut the PVC plastic pipe to the specified length, 10 plastic pipes for one net, and splice the 10 plastic pipes into the overall net frame through 4 plastic tee joints. Net assembly: take out the net clothes attached with fouling organisms from the water area, fix every four net pieces with 8 mm nylon straps, and then reinforce and bundle them with 10 cm thin ropes. Four net pieces form one side of the outdoor aquaculture net. Before assembling the net, take a photo to record the attachment area of each type of fouling organism on each net piece for subsequent area calculation. After assembly, the four corners are tied to the aquaculture frame on the test platform, and a 2 kg counterweight is hung below the net to ensure that the entire outdoor aquaculture net frame is submerged in the water. The assembled net frame is shown in ​ .

[0052] (2) Siganus canaliculatus release

[0053] During the test, the water temperature was 26.7-27.4℃, the salinity was 28.5-33.1, the pH was 6.93-7.69, and the dissolved oxygen was 6.8-7.6 mg / L. The Siganus canaliculatus used in the test were artificially bred in Dongshan Bay, Zhangzhou City, Fujian Province, and were transported by a live water truck to Fuding City, Fujian Province, and were temporarily raised in the Fujian Fuding Test Base of the East China Sea Fisheries Research Institute for 2 months. The Siganus canaliculatus used in the test were selected for their robustness and uniformity, with a body length of (202±13) mm and a body weight of (109±22) g.

[0054] (3) Data collection

[0055] The observation period was once a day, and the attachment area of the five groups of net cages was observed continuously by combining the methods of taking pictures, recording videos, and direct observation with the Osmo Action 5 Pro underwater camera. The daily changes in the attachment area of the four sides of the net clothes of the five groups of net cages were recorded.

[0056] (4) Data processing

[0057] The photos of the fouling organisms attached to the netting taken by the underwater camera were imported into the image processing software Image J. According to the size of the netting, a scale was established, and the fouling organisms on the photographed photos were circled using the irregular image selection function in the software, focusing on calculating the attachment area of each side of the sea squirt on the net cage. Then, according to the regression equation of the sea squirt attachment area and weight, the corresponding weight was calculated. The changes in the weight of the sea squirt on the five groups of net cages were analyzed using EXCEL, and the weight change rate and the feeding efficiency of the Megalobrama elongata on the sea squirt were calculated.

[0058] (5) Data analysis

[0059] ​ The weight change graph of the attached sea squirt is shown. From the weight change curve of the attached sea squirt on the net cages under the five groups of culture densities, the sea squirt biomass weight of the 0 fish / cubic meter group remained almost unchanged, and the removal rate of the sea squirt attached to the net cages by the Megalobrama elongata in the other four groups was 100%.

[0060] The weight of the sea squirt attached to the net cage of the Megalobrama elongata culture density of 5 fish / cubic meter decreased at a relatively stable rate every day, especially from the 2nd day to the 6th day, with a decrease of about 20 grams per day, which belonged to the type of slow but continuous removal. In the 10 fish / cubic meter group, the sea squirt weight decreased dramatically in the first two days, from 109.31 grams to 75.99 grams, a decrease of about 30%, and then gradually slowed down, with an overall medium to stable decline curve. In the 20 fish / cubic meter group, the sea squirt weight decreased dramatically in the first two days, from 157.79 grams to 41.15 grams, a decrease of 116.64 grams, a decrease of 74% in 2 days, and completely removed on the 3rd day, with a fast but slightly sharp speed. In the 40 fish / cubic meter group, it was directly 0 after the 1st day, with extremely high feeding intensity.

[0061] According to the formula FR = [C1 x (1 + K) - C2] / (w x t) (C1: initial weight; C2: final weight; K: loss rate; w: weight of Megalobrama elongata; t: time (days)), the daily feeding efficiency FR of Megalobrama elongata on the attached sea squirt on the net cage under each culture density was calculated. The results are as follows ​Display: In the 5 tails / cubic meter group, the feeding efficiency gradually increased in the first three days, then slightly fluctuated and continuously decreased, and decreased to 0 on the seventh day, showing a pattern of "first increase, then stable, and then decrease", the feeding process was stable and had strong persistence; In the 10 tails / cubic meter group, the feeding efficiency showed a change pattern of "first decrease, then increase, and finally decrease"; In the 20 tails / cubic meter group, it showed a "slow decrease" change pattern, indicating that at a higher density, the fish group has a large feeding intensity in a short period of time, and the sea moss is quickly depleted; In the 40 tails / cubic meter group, the feeding efficiency decreased rapidly on the first day, and tended to 0 after the third day, showing that the sea moss was quickly removed at high density, and the efficiency fluctuated greatly and had a short duration.

[0062] Further, independent sample t test is used to statistically analyze the differences in feeding efficiency between different culture densities, and the results show that there are significant differences between 5 tails / cubic meter and other groups (P<0.05), and there are also significant differences between 10 tails / cubic meter and other groups (P<0.05), indicating that the feeding efficiency is significantly affected by the density.

[0063] In summary, among the four groups of culture density, the longfin yellowtail in the 5 tails / cubic meter group shows higher stability and persistence in feeding behavior, and has better sea moss control effect, which is an ideal ecological control density configuration under the conditions of this test.

[0064] According to the weight change amount of sea moss, the feeding time and the weight of longfin yellowtail under the four groups of culture density, a regression equation is established: AW 海鞘 = -36.48 + 16.36 x t + 0.02667 x W 鱼total , AW 海鞘 : sea moss weight reduction (grams); t: days (days); W 鱼Total : total weight of longfin yellowtail (grams). The significance test result shows that the feeding time (P=0.002) and the total weight of longfin yellowtail (P=0.001) are both significant positive correlation factors, which means that with the passage of time and the increase of the total weight of longfin yellowtail, the rate of sea moss removal is significantly improved. The prediction model provided by the present application can accurately set the fish weight and time in actual production, improve the operation efficiency, save the cost, reasonably configure the fish weight through the model prediction, and avoid resource waste.

[0065] In summary, the present application provides a new biological control method for preventing and treating sea moss and other attached fouling organisms, which has good popularization and application prospect.

[0066] The unexplained part involved in the present application is the same as the prior art or realized by the prior art. The applicant declares that the present application is illustrated by the above-mentioned embodiments to explain the detailed method of the present application, but the present application is not limited to the above-mentioned detailed method, that is, it does not mean that the present application must rely on the above-mentioned detailed method to be implemented. It should be understood by those skilled in the art that any improvement of the present application, equivalent replacement of each raw material of the product of the present application, addition of auxiliary ingredients, selection of specific mode, etc. fall within the protection scope and disclosure scope of the present application.

Claims

1. A biological control method for typical fouling organisms in southern marine aquaculture cages, characterized in that: The steps include: (1) Investigate the composition and community changes of fouling organisms in the aquaculture area through hanging net tests, and determine the attachment of target fouling organisms; (2) Analyze the stomach contents of representative fish in the aquaculture area, screen fish that mainly feed on the target fouling organisms, and identify fish as targets for biological control; (3) The biological control targets determined in step (2) are placed in the test cages, different breeding density gradients are set, and the changes in the attachment area of ​​the target fouling organisms are recorded by underwater photography technology. The weight change and feeding efficiency are calculated based on the image analysis. 目标污损生物 , Total weight of biological control objects W 生物防治对象 A regression equation was established with the feeding time t to predict the reduction of target fouling organisms and guide the control density configuration and release strategy.

2. The biological control method according to claim 1, characterized in that: in, In step (1), a net hanging test is carried out using mesh of a certain specification. The net hanging underwater lasts for 1 to 5 months, and different groups of mesh are set at different depths. The net body is perpendicular to the seabed. The main types and community structure of fouling organisms on the cage are determined. The fouling organisms on the mesh are sampled and analyzed to determine the attachment area of ​​various types of fouling organisms.

3. The biological control method according to claim 1, characterized in that: in, In step (2), high-throughput sequencing technology is used to analyze the fish that feed on the target fouling organisms. The relative abundance of OTUs at the phylum classification level was calculated based on the stomach contents. At the same time, OTUs with high relative abundance were selected and compared with the GenBank database to explore their similar species information. The OTUs sequences belonging to fouling organisms were further screened and a phylogenetic tree was constructed. Finally, combined with the relative abundance data of OTUs of the target fouling organisms, the feeding differences of representative fish in the test area on the target fouling organisms were analyzed to determine the targets of biological control.

4. The biological control method according to claim 1, characterized in that: in, In step (3), the photos of the mesh with fouling organisms attached taken by the underwater camera are imported into the image processing In the software Image J, a scale was established according to the size of the mesh. The irregular image selection function in the software was used to circle the fouling organisms in the photographs. The attachment area of ​​the target fouling organisms on each surface of the cage was calculated. The corresponding weight of the target fouling organism was then calculated based on the regression equation between the attachment area and weight of the target fouling organism. The changes in the weight of the target fouling organisms on cages with different stocking densities were statistically analyzed, and their weight change rate and the feeding efficiency of the biological control subjects on the target fouling organisms were calculated.

5. The biological control method according to claim 4, Its characteristics are: Among them, the feeding efficiency formula is as follows: FR=[C1×(1+K)-C2] / (w×t), Where, FR: daily feeding efficiency; C1: initial weight; C2: final weight; K: loss rate; w: weight of biological control object; t: time, in days; The regression equation is as follows: ΔW 目标污损生物 = -A + B × t + D × W 生物防治对象 , In the formula, ΔW 目标污损生物 : target fouling organism weight reduction, in grams; t: days; W: 生物防治对象 : total weight of biological control object, in grams; A is a constant, B and D are coefficients respectively.

6. The biological control method according to any one of claims 1 to 5, characterized in that: in, The target fouling organism is the ascidian, and the biological control object is the longfin basket fish.

7. The biological control method according to claim 6, characterized in that: in, The stocking density of longfin basket fish is 5~10 per m 3 The specifications are body length 202±13 mm and weight 109±22 g.

8. The biological control method according to claim 6, characterized in that: in, In step (3), the regression equation is established as follows: ΔW 海鞘 = −36.48 + 16.36 × t + 0.02667 ×W 鱼total , In the formula, ΔW 海鞘 : weight loss of ascidian, in grams; t: days; W: 鱼Total : Total weight of longfin basket fish in grams.

9. The application of basket fish in removing sea squirts attached to marine aquaculture cages is characterized in that: The basket fish are mixed cultured in the seawater aquaculture cage.

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