Fish and shellfish polyculture experiment system and verification method

Abstract

The invention discloses a fish and shellfish polyculture experiment system and a verification method, and the system comprises at least two groups of experiment units which operate independently, an intelligent water distribution unit, a water quality on-line monitoring unit, a waste automatic collection unit and a central control unit. Wherein the experiment module comprises a fish culture area, a shellfish culture area, an adjustable mainstream circulation channel and a bypass circulation loop. The verification method comprises the steps of system initialization and experiment grouping, biological putting and feeding calibration, breeding operation under a controlled condition, multi-processing-group synchronous monitoring and sampling and data analysis and efficiency comprehensive evaluation. According to the method, the experimental platform which can accurately simulate the material circulation process of the fish-shellfish polyculture system, realize synchronous comparison of multiple treatment groups and quantitatively evaluate the nutrient interstage material coupling mechanism is constructed, and a scientific basis is provided for an ecological culture mode with low emission and high resource utilization rate.

Description

Technical Field

[0001] This invention relates to the field of aquaculture technology, and in particular to an experimental system and verification method for polyculture of fish and shellfish. Background Technology

[0002] Currently, intensive aquaculture models, especially monoculture of fish, generally face the problem of low feed utilization efficiency. Nutrients that are not effectively absorbed and utilized by fish enter the water in large quantities in the form of uneaten feed and feces, causing the continuous accumulation of nutrients such as nitrogen and phosphorus, leading to water quality deterioration, increased disease risk, and seriously restricting the stability and sustainable development of aquaculture systems.

[0003] To address this challenge, the concept of multitrophic level integrated aquaculture has emerged. This concept utilizes the functional complementarity of organisms at different trophic levels (such as fish and shellfish) to transform waste excreted by one organism into a nutrient source for another, achieving resource recycling and environmental self-repair. However, existing research largely focuses on observing the effectiveness of production applications, lacking a standardized experimental system and verification methods that can operate under precise laboratory control. Specifically, the following technical shortcomings exist: first, it is impossible to accurately quantify the absorption and conversion efficiency of fish farming waste by shellfish; second, it is difficult to clearly elucidate the material coupling mechanisms between organisms at different trophic levels; and third, the comparability of different treatment groups (monoculture and polyculture groups) during experiments is difficult to guarantee, with significant interference from non-experimental factors, leading to insufficient scientific validity and reproducibility of experimental conclusions. Summary of the Invention

[0004] (a) Technical problems to be solved

[0005] To address the shortcomings of existing technologies, this invention constructs an experimental platform that can accurately simulate the material cycling process of a fish-shellfish polyculture system, enable synchronous comparison of multiple treatment groups, and quantitatively evaluate the material coupling mechanism between trophic levels. This provides a scientific basis for an ecological aquaculture model with low emissions and high resource utilization.

[0006] (II) Technical Solution

[0007] To achieve the above objectives, the present invention provides the following technical solution: a fish and shellfish polyculture experimental system, applied to the efficacy verification of multi-trophic-level integrated aquaculture under controlled laboratory conditions, comprising:

[0008] At least two independently operating experimental units, each of which includes a fish and shellfish polyculture experimental module with identical physical structure, used to simulate different aquaculture modes.

[0009] The intelligent water distribution unit is connected to all experimental units and is used to provide and maintain experimental water with completely consistent temperature, salinity, pH value and dissolved oxygen to the experimental units.

[0010] The water quality online monitoring unit has its sampling end placed in the fish farming area, shellfish farming area and internal circulation channel of each set of experimental units, and is used to monitor and record changes in nutrient concentration in the water in real time.

[0011] An automatic waste collection unit is connected to the in-situ fecal separator in each of the experimental units, and is used to periodically and automatically collect fish feces and particulate organic matter generated in the system.

[0012] The central control unit is communicatively connected to the intelligent water distribution unit, the online water quality monitoring unit, and all experimental units, and is used to receive monitoring data and control the operating parameters of each unit.

[0013] As a preferred embodiment, each group of the fish and shellfish polyculture experimental modules includes:

[0014] A group of fish farming areas is equipped with a first automatic feeder and an in-situ manure separator;

[0015] A group of shellfish farming areas, with adjustable attachment substrates inside;

[0016] A set of adjustable main circulation channels fluidly connects the fish farming area and the shellfish farming area, and is equipped with a first water pump and a first flow meter independently controlled by the central control unit;

[0017] A bypass circulation loop is connected in parallel to both ends of the adjustable main circulation channel to maintain water circulation inside the experimental module when the adjustable main circulation channel is closed.

[0018] As a preferred embodiment, the intelligent water distribution unit includes an artificial seawater mother tank, an environmental parameter control system, and multiple high-precision metering pumps. The central control unit controls each metering pump to synchronously and equally inject water into each experimental unit through the following steps:

[0019] A1. Set the target water injection volume Initialize the cumulative water injection volume of each metering pump. ;

[0020] A2. Real-time reading of flow signals from each metering pump to calculate the current cumulative water injection volume. ;

[0021] A3. Calculate the water injection deviation of each pump. = - ;

[0022] A4. Based on water injection deviation The real-time pulse frequency of each metering pump is calculated using a PID control algorithm. = · + · + · ,in , , These are PID control parameters;

[0023] A5. When the cumulative water injection volume of all metering pumps All meet When the value is less than or equal to ε, water injection is stopped, where ε is the allowable error threshold.

[0024] As a preferred embodiment, the online water quality monitoring unit includes a multi-channel automatic sampler and a nutrient analyzer. The central control unit controls the multi-channel automatic sampler to synchronously sample each sampling point in all experimental units through the following steps:

[0025] B1. Set the sampling period T and generate the theoretical sampling time sequence for each sampling point. (j=1,2,...,m);

[0026] B2. At the theoretical sampling time Upon arrival, the sampling valves at the corresponding sampling points of each experimental unit are opened sequentially;

[0027] B3. Record the actual sampling time for each sampling point. And calculate the sampling time deviation. = ;

[0028] B4. When the sampling time deviation at a certain sampling point Exceeding the preset threshold If an anomaly occurs, record the anomaly and adjust the valve opening advance for the next sampling point.

[0029] B5. For the same theoretical sampling time Ensure that the maximum time difference ΔT = max( between the sampling completion times of all experimental units) is achieved. )-min( )≦δ, where k is the experimental unit number and δ is the synchronization time window threshold.

[0030] As a preferred embodiment, the central control unit has preset configuration files for monoculture and polyculture modes. When an experimental unit is set to monoculture mode, the central control unit closes the adjustable main circulation channel corresponding to that unit and starts the bypass circulation loop to maintain the same water circulation state as the polyculture mode unit. When set to polyculture mode, the central control unit opens the adjustable main circulation channel and controls the flow rate of the first water pump according to a preset algorithm or real-time water quality data.

[0031] This invention also proposes a method for verifying fish-shellfish polyculture experiments, which employs a fish-shellfish polyculture experimental system and includes the following steps:

[0032] Step S1, System Initialization and Experiment Grouping:

[0033] At least three experimental groups are set up in the central control unit: fish monoculture group, shellfish monoculture group, and fish-shellfish polyculture group, and at least one experimental unit is assigned to each group; the intelligent water distribution unit is activated through the central control unit, and artificial seawater of the same volume and quality is synchronously injected into all assigned experimental units using a water distribution uniformity control algorithm; according to the set grouping, the central control unit automatically configures the experimental units corresponding to the fish monoculture group and shellfish monoculture group to monoculture mode, and configures the experimental units corresponding to the fish-shellfish polyculture group to polyculture mode;

[0034] Step S2, Biological Release and Feeding Calibration:

[0035] According to the design requirements for stocking density, the same size and quantity of experimental fish were placed in the fish farming area of ​​all experimental units, and the same size and quantity of experimental shellfish were placed in the shellfish farming area of ​​all experimental units; all first automatic feeders were synchronously calibrated through the central control unit to ensure that the amount of feed each time was not statistically significant.

[0036] Step S3, Controlled Aquaculture Operation:

[0037] The experimental system is in operation. The central control unit controls all the first automatic feeders to feed synchronously according to a unified schedule. For the experimental unit in the mixed culture mode, the central control unit drives its adjustable main circulation channel to work, so that the nutrient-containing wastewater generated in the fish farming area flows in a direction through the shellfish farming area. For the experimental unit in the monoculture mode, the central control unit ensures that its bypass circulation loop is operating normally, so that its overall hydrodynamic conditions are consistent with those of the mixed culture unit.

[0038] Step S4: Simultaneous monitoring and sampling of multiple treatment groups:

[0039] During the experiment, the central control unit controlled the online water quality monitoring unit, and used a synchronous sampling control algorithm to periodically and synchronously sample and analyze each monitoring point in all experimental units to obtain real-time concentration data of ammonia nitrogen, nitrite, nitrate and reactive phosphorus. At the same time, the central control unit controlled the automatic waste collection unit to periodically and automatically collect and dispense the feces generated by each experimental unit.

[0040] Step S5: Data Analysis and Comprehensive Performance Evaluation

[0041] After the experiment, carbon and nitrogen stable isotope analysis was performed on the collected waste and biological tissue samples. The central control unit summarized all water quality data and sample analysis results. By comparing the water quality data of the fish monoculture group and the fish-shellfish polyculture group, the nutrient removal efficiency of the polyculture system was calculated. Combined with the stable isotope analysis results, the isotope mixing model was used to quantitatively assess the absorption ratio of nutrients from fish farming waste by shellfish, and material balance models for different treatment groups were constructed to clarify the material coupling relationship between different trophic levels.

[0042] As a preferred embodiment, in step S3, the central control unit controls the flow rate of the first water pump based on real-time water quality data, and the specific control rules are as follows:

[0043] The safe threshold for ammonia nitrogen concentration in fish farming areas is set as follows: Real-time monitoring value ;

[0044] when ≤ At the same time, maintain the base flow rate Q0 of the first water pump;

[0045] when > At that time, the flow rate is dynamically adjusted according to the following formula:

[0046] Q(t) = Q0 × [1 + α × ( ) / ];

[0047] Wherein, α is the flow rate adjustment coefficient, with a value ranging from 0.5 to 2.0;

[0048] Meanwhile, to ensure the filter-feeding efficiency of shellfish on particulate matter, the hydraulic retention time (HRT) in the shellfish farming area should be controlled to be no less than 30 minutes, i.e., Q(t) ≤ ,in This refers to the water volume in the shellfish farming area.

[0049] As a preferred embodiment, step S5, which uses an isotope mixing model to quantitatively assess the absorption ratio of nutrients from fish farming waste by shellfish, specifically includes the following sub-steps:

[0050] Step S51: Determine the carbon stable isotope δ13C and nitrogen stable isotope δ15N values ​​of feed, fish feces, shellfish tissue in monoculture group, and shellfish tissue in fish-shellfish polyculture group;

[0051] Step S52: Construct an isotopic mixing model of shellfish nutrient sources:

[0052] = · + · + · ;

[0053] Where X represents 13C or 15N, The isotopic values ​​of shellfish tissue in the fish-shellfish polyculture group are shown. The isotopic value of the feed. The isotopic values ​​are from fish feces. These are the isotopic values ​​of the monotrophic mollusks' tissues. , , These represent the contribution percentages from each source, and =1;

[0054] Step S53: By solving the above system of equations, the proportion of nutritional contribution of fish excrement to shellfish growth is obtained. This study quantitatively verified the ability of shellfish to absorb and convert nutrients from fish farming waste.

[0055] As a preferred embodiment, step S5, which calculates the nutrient removal efficiency of the polyculture system, specifically includes the following sub-steps:

[0056] Step S54: Calculate the cumulative nutrient salts in the fish monoculture group and the fish-shellfish polyculture group during the same time period:

[0057] = )dt;

[0058] = - )dt;

[0059] in, The nutrient concentration at time t in the monoculture group of fish is given. The nutrient concentration at time t in the fish and shellfish polyculture group. This represents the initial nutrient concentration.

[0060] Step S55: Calculate the nutrient removal rate of the fish and shellfish polyculture system:

[0061] R = ( - ) / ×100%;

[0062] The removal rates of ammonia nitrogen, reactive phosphorus, nitrite nitrogen, and nitrate nitrogen were calculated separately to evaluate the regulatory effect of the mixed-culture model on different nutrients.

[0063] As a preferred embodiment, the experimental fish is *Scorpionichthys schlegelii*, the experimental shellfish is *Crassostrea gigas*, and the culture period is 45 days; in step S4, the sampling frequency is set to: once every 2 days in the first 10 days of the experiment, and once every 5 days thereafter; in step S5, the stable isotope analysis adopts the dual tracer method of carbon stable isotope and nitrogen stable isotope.

[0064] (III) Beneficial Effects

[0065] Compared with the prior art, the present invention provides a fish and shellfish polyculture experimental system and verification method, which has the following beneficial effects:

[0066] I. This invention utilizes a PID control algorithm in an intelligent water distribution unit to achieve synchronized and equal water injection across all experimental units, controlling injection deviation within the ε threshold, thus ensuring precise consistency of initial water volume across all treatment groups from the outset. Simultaneously, the bypass circulation loop design allows monoculture and polyculture groups to maintain the same water circulation state even when the main channel is closed, eliminating systematic errors caused by differences in hydrodynamic conditions.

[0067] Second, this invention also uses an integral method to calculate the nutrient removal rate, replacing the traditional endpoint concentration comparison with the cumulative amount throughout the process. This more accurately reflects the overall control efficiency of the polyculture system throughout the entire breeding cycle and avoids the evaluation bias caused by fluctuations in single-point data.

[0068] Third, this invention dynamically adjusts the water flow rate based on real-time water quality data. When the ammonia nitrogen concentration exceeds the standard, the flow rate is automatically increased to accelerate wastewater transport. Simultaneously, the hydraulic retention time is constrained to be no less than 30 minutes to ensure shellfish filter-feeding efficiency, forming a closed-loop control system of "monitoring-feedback-regulation," significantly improving the system's adaptability and operational stability. Attached Figure Description

[0069] Figure 1 This is a schematic diagram of the overall structure of the fish and shellfish polyculture experimental system of the present invention;

[0070] Figure 2 This is a schematic diagram of the internal structure of the experimental unit of the present invention;

[0071] Figure 3 The flowchart is as follows: This invention provides a method for verifying the polyculture experiment of fish and shellfish. Figure 1 ;

[0072] Figure 4 The flowchart is as follows: This invention provides a method for verifying the polyculture experiment of fish and shellfish. Figure 2 ;

[0073] Figure 5 The flowchart is as follows: This invention provides a method for verifying the polyculture experiment of fish and shellfish. Figure 3 . Detailed Implementation

[0074] To better understand the purpose, structure, and function of this invention, the following will further explain the experimental system and verification method for fish and shellfish polyculture of this invention in conjunction with the accompanying drawings and specific embodiments.

[0075] Example 1

[0076] refer to Figure 1 The present invention provides a fish and shellfish polyculture experimental system, comprising:

[0077] It includes at least two independently operating experimental units, an intelligent water distribution unit, an online water quality monitoring unit, an automatic waste collection unit, and a central control unit.

[0078] This embodiment includes three experimental units: a fish monoculture group, a shellfish monoculture group, and a fish-shellfish polyculture group. Each experimental unit is a physically identical fish-shellfish polyculture experimental module to ensure structural comparability among the treatment groups. The intelligent water distribution unit in this embodiment is connected to all experimental units, providing and maintaining experimental water with completely consistent temperature, salinity, pH, and dissolved oxygen. The core of the intelligent water distribution unit lies in the water distribution uniformity control algorithm of the central control unit. The algorithm uses incremental PID control, adjusting the pulse frequency of the metering pump to achieve precise control of the cumulative water injection volume, ensuring precise consistency of the initial water volume in each unit. The online water quality monitoring unit has sampling points placed in the fish farming area, shellfish farming area, and internal circulation channel of each experimental unit to monitor and record changes in nutrient concentration in the water in real time. A synchronous sampling control algorithm ensures the comparability of all sampling points over time. In this embodiment, the automatic waste collection unit is connected to the in-situ fecal separator in each experimental unit, and is used to periodically and automatically collect fish feces and particulate organic matter generated in the system, providing a sample basis for subsequent stable isotope analysis.

[0079] Specifically, such as Figure 2 As shown, the specific structure of each group of fish and shellfish polyculture experimental modules in this embodiment includes:

[0080] Fish farming area: Contains transparent cylindrical acrylic tanks with a conical bottom for easy waste sedimentation and collection. Inside are an automatic feeder and an in-situ waste separator. The automatic feeder is controlled by a central control unit, enabling timed and quantitative feeding. The in-situ waste separator is a conical collection hopper, its bottom connected to an automatic waste collection unit via pipes. A gentle bottom water flow promptly flushes out fresh fish waste, preventing it from prolonged soaking and decomposition in water.

[0081] Shellfish farming area: Utilizing a multi-layered, three-dimensional structure with adjustable attachment substrates inside. The substrates are made of non-toxic plastic and can be arranged in multiple mesh-frame layers for Pacific oysters and other shellfish to attach and grow. By increasing or decreasing the number of substrates and adjusting the spacing between layers, the farming density and spatial distribution of the shellfish can be flexibly controlled.

[0082] Adjustable main circulation channel: This channel connects the fish farming area and the shellfish farming area, and is equipped with a first water pump and a first flow meter. The first water pump is independently controlled by a central control unit, allowing for precise adjustment of the water flow direction and velocity. When set to "mixed culture mode," this channel opens, allowing nutrient-containing wastewater from the fish farming area to flow directionally through the shellfish farming area.

[0083] Bypass circulation loop: Connected in parallel to both ends of the adjustable main circulation channel. When set to "single-culture mode", the central control unit closes the adjustable main circulation channel and opens the bypass circulation loop at the same time, so that the water inside the experimental module can circulate independently to maintain the same overall water volume, hydrodynamic conditions and filtration load as the mixed-culture mode experimental module.

[0084] In one embodiment, the intelligent water distribution unit of the present invention includes an artificial seawater mother tank, an environmental parameter control system, and multiple high-precision metering pumps.

[0085] The artificial seawater master tank is a large-capacity storage tank (500L in this embodiment) used to prepare a large quantity of artificial seawater at one time, ensuring the consistency of water quality in all experimental units. The environmental parameter control system is connected to the artificial seawater master tank and includes a heating / cooling device, an oxygenation device, and a pH adjustment device, used to uniformly control the temperature (controlled at 18±1℃), dissolved oxygen (maintained above 6mg / L), and pH value (adjusted to 8.1±0.1) of the water in the master tank.

[0086] The inlet ends of multiple high-precision metering pumps (three are set in this embodiment, corresponding to the number of experimental units) are all connected to the artificial seawater mother tank, and the outlet ends are connected to each experimental unit in a corresponding manner.

[0087] In one embodiment, the central control unit controls each metering pump to synchronously and equally inject water into each experimental unit through the following steps:

[0088] A1. Set the target water injection volume Initialize the cumulative water injection volume of each metering pump. ;

[0089] A2. Real-time reading of flow signals from each metering pump to calculate the current cumulative water injection volume. ;

[0090] A3. Calculate the water injection deviation of each pump. = - ;

[0091] A4. Based on water injection deviation The real-time pulse frequency of each metering pump is calculated using a PID control algorithm. = · + · + · ,in , , These are PID control parameters;

[0092] A5. When the cumulative water injection volume of all metering pumps All meet When the value is less than or equal to ε, water injection is stopped, where ε is the allowable error threshold. In this embodiment, ε is set to (0.1L).

[0093] Through the above control (water distribution uniformity control algorithm), the final water injection volumes of the three experimental units were 50.03L, 49.98L and 50.02L respectively, with a maximum deviation of 0.05L, which is much smaller than the allowable error threshold, thus achieving high-precision water distribution uniformity.

[0094] In this embodiment, the online water quality monitoring unit includes a multi-channel automatic sampler and a nutrient analyzer.

[0095] The sampling probes of the multi-channel automatic sampler are inserted into the fish farming area, shellfish farming area, and main circulation channel of each experimental unit. This embodiment sets up 9 sampling points (3 units × 3 locations). The nutrient analyzer is a multi-channel online nutrient analyzer that can automatically analyze ammonia nitrogen (NH4+) in water samples. + -N), nitrite nitrogen (NO2) - -N), nitrate nitrogen (NO3) - -N) and active phosphorus (PO4) 3- -P) concentration.

[0096] In one embodiment, the central control unit controls the multi-channel automatic sampler to synchronously sample each sampling point of all experimental units through the following steps:

[0097] B1. Set the sampling period T and generate the theoretical sampling time sequence for each sampling point. (j=1,2,...,m);

[0098] B2. At the theoretical sampling time Upon arrival, the sampling valves at the corresponding sampling points of each experimental unit are opened sequentially;

[0099] B3. Record the actual sampling time for each sampling point. And calculate the sampling time deviation. = ;

[0100] B4. When the sampling time deviation at a certain sampling point Exceeding the preset threshold If an anomaly occurs, record the anomaly and adjust the valve opening advance for the next sampling point.

[0101] B5. For the same theoretical sampling time Ensure that the maximum time difference ΔT = max( between the sampling completion times of all experimental units) is achieved. )-min( ) ≦δ, where k is the experimental unit number and δ is the synchronization time window threshold. (In this embodiment, δ is set to 5min).

[0102] Through the above control (synchronous sampling control algorithm), the actual sampling time of all sampling points in this embodiment is completed within 9:00±1.5min, and the maximum time difference between different units in the same round is 3.2min, which meets the requirement of δ≤5min, effectively eliminating the interference of daily water quality changes caused by sampling time difference.

[0103] In one embodiment, the central control unit of this embodiment has preset configuration files for "single-culture mode" and "mixed-culture mode". When a certain experimental unit is set to "single-culture mode", the central control unit closes the adjustable main circulation channel corresponding to that unit and starts the bypass circulation loop, setting the water pump flow rate of the bypass loop. This ensures that the total circulation flow rate of the unit is consistent with that of the mixed culture mode (set to 5L / min in this embodiment). When set to "mixed culture mode", the central control unit opens the adjustable main circulation channel and dynamically controls the flow rate of the first water pump based on real-time water quality data.

[0104] Example 2

[0105] like Figure 2-5 As shown, this embodiment uses Scorpionfish and Pacific oyster as experimental subjects, and verifies them according to the following methods and steps:

[0106] Step S1: System Initialization and Experiment Grouping

[0107] Three experimental groups were set up in the central control unit: a fish monoculture group (assignment experimental unit), a shellfish monoculture group (assignment experimental unit), and a fish-shellfish polyculture group (assignment experimental unit). The intelligent water distribution unit was activated, and artificial seawater of equal volume (50L) and quality was synchronously injected into the three experimental units according to the equal-volume water injection steps in Example 1. Based on the group settings, the central control unit automatically configured the fish monoculture group and the shellfish monoculture group as "monoculture mode," and configured the fish-shellfish polyculture group as "polyculture mode."

[0108] Step S2: Biological introduction and feeding calibration

[0109] In the fish monoculture group, 15 rockfish (average weight 50±2g) were stocked in the fish farming area, while the shellfish farming area was left empty. In the shellfish monoculture group, 30 Pacific oysters (average shell length 5±0.3cm) were stocked in the shellfish farming area, while the fish farming area was left empty. In the fish-shellfish polyculture group, 15 rockfish were stocked in the fish farming area, and 30 Pacific oysters were stocked in the shellfish farming area. All the first automatic feeders were synchronized and calibrated by the central control unit to ensure that the feeding amount was 3% of the fish's body weight each time (i.e., approximately 2.25g per unit per feeding). All organisms were temporarily housed in the system for 7 days to acclimatize to the environment.

[0110] Step S3: Controlled Aquaculture Operation

[0111] The culture cycle was set at 45 days. The central control unit controlled all first-stage automatic feeders to feed synchronously according to a unified schedule (8:00 AM and 4:00 PM daily). For the polyculture units, the central control unit drove the adjustable main circulation channel to direct the nutrient-rich wastewater from the fish culture area through the shellfish culture area. For the monoculture units (fish monoculture and shellfish monoculture), the central control unit ensured the normal operation of their bypass circulation loops, maintaining a total circulation flow rate of 5 L / min, consistent with the polyculture units. Table 1 below summarizes the average concentrations of the main water quality indicators for each treatment group during the experiment (average of all sampling points over 45 days):

[0112] Table 1

[0113]

[0114] As shown in the table, the concentrations of ammonia nitrogen, nitrite nitrogen, nitrate nitrogen, and reactive phosphorus in the fish-shellfish polyculture group (FS group) were significantly lower than those in the fish monoculture group (F group) (P<0.05). Compared with the shellfish monoculture group (S group), ammonia nitrogen and reactive phosphorus were slightly higher, but the difference was not significant (P>0.05). This indicates that shellfish in the polyculture system effectively absorbed and converted the nutrients excreted by fish, resulting in a significant improvement in water quality.

[0115] Step S4: Synchronous monitoring and sampling of multiple treatment groups

[0116] During the experiment, the central control unit controlled the online water quality monitoring unit to perform periodic synchronous sampling and analysis at each monitoring point in all experimental units according to the synchronous sampling steps in Example 1. The sampling frequency was set as follows: once every 2 days for the first 10 days of the experiment, and once every 5 days thereafter. The concentrations of ammonia nitrogen, nitrite, nitrate, and reactive phosphorus were measured each time. At the same time, the central control unit controlled the automatic waste collection unit to automatically collect and dispense the feces generated by each experimental unit every 3 days, and store them at low temperature (-20℃) for later use.

[0117] Step S5: Data Analysis and Comprehensive Performance Evaluation

[0118] After the experiment, carbon and nitrogen stable isotope analysis was performed on the collected waste and biological tissue samples.

[0119] (1) Calculation of nutrient removal efficiency

[0120] Calculate the cumulative nutrient salts in the fish monoculture group and the fish-shellfish polyculture group over 45 days:

[0121] = )dt;

[0122] = - )dt;

[0123] Taking ammonia nitrogen as an example, the calculation is as follows: =12.45 mg / L·d, =6.83 mg / L·d, then the ammonia nitrogen removal rate R = (12.45 - 6.83) / 12.45 × 100% = 45.1%. Similarly, the active phosphorus removal rate is calculated to be 38.6%, the nitrite nitrogen removal rate is 41.2%, and the nitrate nitrogen removal rate is 22.3%.

[0124] (2) Quantitative assessment of isotope mixing model

[0125] The δ13C and δ15N values ​​of feed, fish feces, shellfish tissue in monoculture, and shellfish-co-culture were measured. The results are as follows: δ13 =-18.5‰, δ13 =-19.2‰, δ13 =-20.1‰ (Belamcanda chinensis group), δ13 =-19.4‰ (fish and shellfish polyculture group). Constructing an isotopic mixing model:

[0126] δ13 = ·δ13 + ·δ13 + ·δ13

[0127] Substituting, we get: -19.4 = ×(-18.5)+ ×(-19.2)+ ×(-20.1)

[0128] Combination =1, solving for the equation yields... =0.35, meaning that fish feces contribute 35% of the nutrients needed for shellfish growth. Similarly, based on δ15N, the following is calculated... =0.33, with an average value of 34%. This result quantitatively verifies the ability of shellfish to absorb and transform nutrients from fish farming waste.

[0129] This embodiment, through specific aquaculture experiments combined with water quality monitoring and stable isotope tracing technology, quantitatively confirmed the significant nutrient removal effect of the fish-shellfish polyculture system on aquaculture water, and revealed the proportion of contribution of shellfish to the absorption of nutrients from fish waste. The experimental results are highly consistent with the method proposed in this invention, fully verifying the scientific nature and effectiveness of the technical solution of this invention.

[0130] It is understood that the present invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Furthermore, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of the present invention.

Claims

1. A fish-shellfish polyculture experimental system, used for efficacy verification in multi-trophic-level integrated aquaculture under controlled laboratory conditions, characterized in that, include: At least two independently operating experimental units, each of which includes a fish and shellfish polyculture experimental module with identical physical structure, used to simulate different aquaculture modes. The intelligent water distribution unit is connected to all experimental units and is used to provide and maintain experimental water with completely consistent temperature, salinity, pH value and dissolved oxygen to the experimental units. The water quality online monitoring unit has its sampling end placed in the fish farming area, shellfish farming area and internal circulation channel of each set of experimental units, respectively, to monitor and record changes in nutrient concentration in the water in real time; An automatic waste collection unit is connected to the in-situ fecal separator in each of the experimental units, and is used to periodically and automatically collect fish feces and particulate organic matter generated in the system. The central control unit is communicatively connected to the intelligent water distribution unit, the online water quality monitoring unit, and all experimental units, and is used to receive monitoring data and control the operating parameters of each unit.

2. The fish and shellfish polyculture experimental system according to claim 1, characterized in that, Each group of fish and shellfish polyculture experimental modules includes: A group of fish farming areas is equipped with a first automatic feeder and an in-situ manure separator; A group of shellfish farming areas, equipped with adjustable attachment substrates; A set of adjustable main circulation channels fluidly connects the fish farming area and the shellfish farming area, and is equipped with a first water pump and a first flow meter independently controlled by the central control unit; A bypass circulation loop is connected in parallel to both ends of the adjustable main circulation channel to maintain water circulation inside the experimental module when the adjustable main circulation channel is closed.

3. The fish and shellfish polyculture experimental system according to claim 1, characterized in that, The intelligent water distribution unit includes an artificial seawater mother tank, an environmental parameter control system, and multiple high-precision metering pumps. The central control unit controls each metering pump to synchronously and equally inject water into each experimental unit through the following steps: A1. Set the target water injection volume Initialize the cumulative water injection volume of each metering pump. ; A2. Real-time reading of flow signals from each metering pump to calculate the current cumulative water injection volume. ; A3. Calculate the water injection deviation of each pump. = - ; A4. Based on water injection deviation The real-time pulse frequency of each metering pump is calculated using a PID control algorithm. = · + · + · ,in , , These are PID control parameters; A5. When the cumulative water injection volume of all metering pumps All meet When the value is less than or equal to ε, water injection is stopped, where ε is the allowable error threshold.

4. The fish and shellfish polyculture experimental system according to claim 3, characterized in that... The online water quality monitoring unit includes a multi-channel automatic sampler and a nutrient analyzer. The central control unit controls the multi-channel automatic sampler to synchronously sample each sampling point in all experimental units through the following steps: B1. Set the sampling period T and generate the theoretical sampling time sequence for each sampling point. (j=1,2,...,m); B2. At the theoretical sampling time Upon arrival, the sampling valves at the corresponding sampling points of each experimental unit are opened sequentially; B3. Record the actual sampling time for each sampling point. And calculate the sampling time deviation. = ; B4. When the sampling time deviation at a certain sampling point Exceeding the preset threshold If an anomaly occurs, record the anomaly and adjust the valve opening advance for the next sampling point. B5. For the same theoretical sampling time Ensure that the maximum time difference ΔT = max( between the sampling completion times of all experimental units) is achieved. )-min( )≦δ, where k is the experimental unit number and δ is the synchronization time window threshold.

5. The fish and shellfish polyculture experimental system according to claim 4, characterized in that, The central control unit has preset configuration files for monoculture and polyculture modes. When an experimental unit is set to monoculture mode, the central control unit closes the adjustable main circulation channel corresponding to that unit and starts the bypass circulation loop to maintain the same water circulation state as the polyculture mode unit. When set to polyculture mode, the central control unit opens the adjustable main circulation channel and controls the flow rate of the first water pump according to a preset algorithm or real-time water quality data.

6. A method for verifying fish-shellfish polyculture experiments, employing the system described in any one of claims 1-5, characterized in that, Includes the following steps: Step S1, System Initialization and Experiment Grouping: At least three experimental groups are set up in the central control unit: fish monoculture group, shellfish monoculture group, and fish-shellfish polyculture group, and at least one experimental unit is assigned to each group; the intelligent water distribution unit is activated through the central control unit, and artificial seawater of the same volume and quality is synchronously injected into all assigned experimental units using a water distribution uniformity control algorithm; according to the set grouping, the central control unit automatically configures the experimental units corresponding to the fish monoculture group and shellfish monoculture group to monoculture mode, and configures the experimental units corresponding to the fish-shellfish polyculture group to polyculture mode; Step S2, Biological Release and Feeding Calibration: According to the design requirements for stocking density, the same size and quantity of experimental fish were placed in the fish farming area of ​​all experimental units, and the same size and quantity of experimental shellfish were placed in the shellfish farming area of ​​all experimental units; all first automatic feeders were synchronously calibrated through the central control unit to ensure that the amount of feed each time was not statistically significant. Step S3, Controlled Aquaculture Operation: The experimental system is in operation. The central control unit controls all the first automatic feeders to feed synchronously according to a unified schedule. For the experimental unit in the mixed culture mode, the central control unit drives its adjustable main circulation channel to work, so that the nutrient-containing wastewater generated in the fish farming area flows in a direction through the shellfish farming area. For the experimental unit in the monoculture mode, the central control unit ensures that its bypass circulation loop is operating normally, so that its overall hydrodynamic conditions are consistent with those of the mixed culture unit. Step S4: Simultaneous monitoring and sampling of multiple treatment groups: During the experiment, the central control unit controlled the online water quality monitoring unit, and used a synchronous sampling control algorithm to periodically and synchronously sample and analyze each monitoring point in all experimental units to obtain real-time concentration data of ammonia nitrogen, nitrite, nitrate and reactive phosphorus. At the same time, the central control unit controlled the automatic waste collection unit to periodically and automatically collect and dispense the feces generated by each experimental unit. Step S5: Data Analysis and Comprehensive Performance Evaluation After the experiment, carbon and nitrogen stable isotope analysis was performed on the collected waste and biological tissue samples. The central control unit summarized all water quality data and sample analysis results. By comparing the water quality data of the fish monoculture group and the fish-shellfish polyculture group, the nutrient removal efficiency of the polyculture system was calculated. Combined with the stable isotope analysis results, the isotope mixing model was used to quantitatively assess the absorption ratio of nutrients from fish farming waste by shellfish, and material balance models for different treatment groups were constructed to clarify the material coupling relationship between different trophic levels.

7. The experimental verification method for fish and shellfish polyculture according to claim 6, characterized in that... In step S3, the central control unit controls the flow rate of the first water pump based on real-time water quality data. The specific control rules are as follows: The safe threshold for ammonia nitrogen concentration in fish farming areas is set as follows: Real-time monitoring value ; when ≤ At the same time, maintain the base flow rate Q0 of the first water pump; when > At that time, the flow rate is dynamically adjusted according to the following formula: Q(t)=Q0×[1+α×( ) / ]; Wherein, α is the flow rate adjustment coefficient, with a value ranging from 0.5 to 2.0; Meanwhile, to ensure the filter-feeding efficiency of shellfish on particulate matter, the hydraulic retention time (HRT) in the shellfish farming area should be controlled to be no less than 30 minutes, i.e., Q(t) ≤ ,in This refers to the water volume in the shellfish farming area.

8. The experimental verification method for fish and shellfish polyculture according to claim 6, characterized in that, In step S5, the isotope mixing model is used to quantitatively assess the proportion of nutrients absorbed by shellfish from fish farming waste, which specifically includes the following sub-steps: Step S51: Determine the carbon stable isotope δ13C and nitrogen stable isotope δ15N values ​​of feed, fish feces, shellfish tissue in monoculture group, and shellfish tissue in fish-shellfish polyculture group; Step S52: Construct an isotopic mixing model of shellfish nutrient sources: = · + · + · ； Where X represents 13C or 15N, The isotopic values ​​of shellfish tissue in the fish-shellfish polyculture group are shown. The isotopic value of the feed. The isotopic values ​​are from fish feces. These are the isotopic values ​​of the monotrophic mollusks' tissues. , , These represent the contribution percentages from each source, and =1; Step S53: By solving the above system of equations, the proportion of nutritional contribution of fish excrement to shellfish growth is obtained. This study quantitatively verified the ability of shellfish to absorb and convert nutrients from fish farming waste.

9. The experimental verification method for fish and shellfish polyculture according to claim 8, characterized in that, In step S5, the nutrient removal efficiency of the polyculture system is calculated, which specifically includes the following sub-steps: Step S54: Calculate the cumulative nutrient salts in the fish monoculture group and the fish-shellfish polyculture group during the same time period: = )dt; = - )dt; in, The nutrient concentration at time t in the monoculture group of fish is given. The nutrient concentration at time t in the fish and shellfish polyculture group. This represents the initial nutrient concentration. Step S55: Calculate the nutrient removal rate of the fish and shellfish polyculture system: R=（ － ） / ×100%； The removal rates of ammonia nitrogen, reactive phosphorus, nitrite nitrogen, and nitrate nitrogen were calculated separately to evaluate the regulatory effect of the mixed-culture model on different nutrients.

10. The experimental verification method for fish and shellfish polyculture according to claim 6, characterized in that, The experimental fish was *Scorpionichthys schlegelii*, and the experimental shellfish was *Crassostrea gigas*. The culture period was 45 days. In step S4, the sampling frequency was set to once every 2 days for the first 10 days of the experiment, and once every 5 days thereafter. In step S5, the stable isotope analysis used a dual tracer method with carbon stable isotopes and nitrogen stable isotopes.

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