Aquaculture Structure Research Articles

Risk Factors of Mariculture Supply Chain Based on Green Development: A Case Study of Changhai County in China

China is a global leader in aquaculture, and mariculture has become an important part of Chinese agriculture and one of the important growth points of the rural economy. However, environmental changes and industrial restructuring have brought new risks to the aquaculture supply chain. Recently, people have also paid more and more attention to the marine environment because a good marine environment is the foundation of the healthy development of mariculture. This study analyses the risks in the aquaculture supply chain from the perspective of the marine environment, using Changhai County, Liaoning Province, as an example. The study identified marine environmental issues such as over-sized aquaculture, irrational aquaculture structure, resource integration gaps, nuclear wastewater discharge and offshore oil pollution. Recommendations included restructuring aquaculture, professional training, establishing cooperative mechanisms, and improving seafood quality testing and marine environment monitoring. Addressing these challenges is essential to ensure the stable and healthy development of seafood markets and the sustainability of the aquaculture industry.

Hydrodynamic interactions between the cylinder and nets of a typical offshore aquaculture structure in steady current: Numerical investigation and coupling mechanism

The expansion of aquaculture fish farms into deep sea has become a trend today. Several new types of offshore fish farming structures have been designed and tested in real sea, a typical of which is the semi-submersible structure. To ensure structural safety in harsh sea environment, detailed investigations on the hydrodynamic characteristics of offshore aquaculture structures are necessary and meaningful. The study focuses on the basic components of a semi-submersible net cage, namely the combined cylinder-net structure, and conducts CFD-based numerical research on its hydrodynamic coupling characteristics under uniform flow. The net structure is numerically simulated based on the porous media model. The drag and lift force and corresponding flow field of only the cylinder, only the nets, and the combined cylinder-net structure are measured under different inflow angles and solidity ratios of nets. The results indicate that the presence of the cylinder increases the drag of nets, and its impact on lift force of nets is closely related to the inflow angle. On the other hand, the presence of the net structure also amplifies the resistance of the cylinder. Meanwhile, the disturbance law of the flow field caused by the cylinder and the net structure is analyzed. By combining numerical and existing experimental results, the hydrodynamic coupling mechanism between the cylinder and the net structure is preliminarily revealed. This study indicates that when conducting hydrodynamic analysis of offshore structures such as the new semi-submersible net cage, the hydrodynamic interaction between the columns and the net structure should be considered.

Dynamic responses of a semi-submersible integrated wind-energy-aquaculture structure under regular and irregular waves

Offshore aquaculture has expanded significantly, and offshore wind energy is more abundant and stable than it is on land. The integration of aquaculture facilities and offshore wind-turbine technology to build a comprehensive platform has both scientific and theoretical significance. To further investigate an integrated wind-energy and aquaculture structure and its dynamic response characteristics, we performed physical model experiments to investigate the motion response properties of the new wind-energy-aquaculture integrated structure. Regular and irregular wave experiments were conducted on a wave flume. The motion responses and mooring line tensions of the platform modules were obtained. Under regular wave conditions, the three degree-of-freedom motion response of the model under two different mooring configurations exhibit the similar trend as the wave height and wave frequency increased. The heave responses under different mooring configurations were generally consistent, whereas the surge responses exhibited low-frequency characteristics. The mooring line tensions of the taut mooring configuration changed significantly with the wave parameters, whereas those with catenary mooring exhibited minor changes. Under irregular wave conditions, structures with catenary mooring systems exhibited smaller motion responses, thereby maintaining their stability.

Application of a VOF Multiphase Flow Model for Issues concerning Floating Raft Aquaculture

Floating raft aquaculture has gradually become a mainstream aquaculture model in the waters of Changhai County, Dalian. To quantitatively describe the impact of floating raft aquaculture facilities on the hydrodynamic environment of nearby sea areas, in this study, we took a single floating raft aquaculture structure as the research object and built a numerical prediction model for water flows passing through the floating raft aquaculture structure using a six-degree-of-freedom VOF (volume of fluid) multiphase flow simulation method based on an overset moving mesh system. Then, we verified the numerical model by utilizing oblique hydraulic jumps and water flows passing through a submerged bar. As shown by the findings, the simulated values are in good agreement with the theoretical solutions and measured values, indicating that the model features high precision and great stability. The impact of the raft area on the hydrodynamic force was introduced into the source term of an equation for consideration. In order to further determine the hindering effect of the raft body on the water body, transport equations and the tracer method were used to simulate the impact of floating raft aquaculture facilities on the water exchange performance of nearby sea areas. This study shows that the VOF multiphase flow model can be easily and accurately applied to studies on floating raft aquaculture, which can greatly reduce the limitations of experiments that utilize pure hydraulic models, wherein the impacts of floating raft aquaculture facilities on hydrodynamic force are generally considered simply based on observations, water roughness or the secondary drag force coefficient, thereby effectively improving the scientific understanding of the physical mechanism involved in floating raft aquaculture.

Marine algae biomass energy source is increasing getting approval from policy maker and community. Beside production of seaweed for biomass energy, seaweed plantation has benefit for food, cosmetic, gelatin and pharmaceutical products. Large production of biomass will require deployment of very large multibody floating structure offshore. To ensure that the system is reliable, design needs to be built, a mooring

Marine algae biomass energy source is increasing getting approval from policy maker and community. Beside production of seaweed for biomass energy, seaweed plantation has benefit for food, cosmetic, gelatin and pharmaceutical products. Large production of biomass will require deployment of very large multibody floating structure offshore. To ensure that the system is reliable, design needs to be built, a mooring component for the mooring system, need to be properly sized to provide reliable strength for position keeping. This paper present, result of hydrodynamic test carried in UTM lab to determine coefficient required for the design and simulation of mooring system for very large floating structure for offshore aquaculture structure for ocean plantation, the paper also present safety and efficiency of the mooring system. Hydrodynamic test is traditionally used to secure coefficient require for design for environment for ship structure and offshore platform hydrodynamic interaction. The case of seaweed biomass is unique because the seaweed interacts directly and moves with the environment. The obtained the coefficient is used to model the static moorings system that assess the tension, tilt, safe mass and motion of the mooring components. Interpolated time dependent currents from the towing tank are used to estimate dynamic response of the mooring as well as the draft of the mooring components, the overall analysis is use to select required mooring components of the system. The outcome of the test presented in this paper will help for future development of offshore aquaculture system and multibody system deployment and analysis

DYNAMIC SIMULATION OF AN OFFSHORE AQUACULTURE STRUCTURE SUBJECTED TO COMBINED WAVE AND CURRENT CONDITIONS

Abstract The reliable design of offshore aquaculture structure (OAS) for fish farming in the open ocean is vital to the marine aquaculture industry in the future. However, the lack of easy-to-access numerical tools for the dynamic analysis of OAS challenges the development of marine aquaculture. This article presents a newly developed numerical library under an open-source, finite-element analysis code, Code_Aster, enabling the dynamic analysis of OAS. A numerical model of OAS is first developed using the present numerical library, and then validated against published experiments. The validation shows a good agreement in terms of structural motions and tensions in mooring lines. Subsequently, the dynamic responses of this model are analyzed under irregular waves and current conditions from field measurements on an offshore fish farm site. The results indicate that a negative mean pitch angle will occur when the current velocity is large.

Numerical and experimental investigations of hydrodynamics of a fully-enclosed pile-net aquaculture pen in regular waves

Large-scale aquaculture pen is one of the essential modes of offshore aquaculture being explored in recent years. In contrast to cage farming, the advantages are more significant as the larger cultural space for fish swimming, the closer-to-nature environment, and the improved ecological quality of fish. As a novel offshore aquaculture structure, fully-enclosed pile-net aquaculture pens (FPAPs) are generally deployed in exposed oceans, where severe waves and currents are of great dominance. The hydrodynamic characteristics of FPAPs in offshore areas deserve further investigation. In this paper, the numerical model of a typical FPAP in waves is proposed based on the finite element method (FEM), then wave loads on and induced motion responses of the FPAP are analyzed. The results show that the maximum loads on the structure and the maximum displacement of piles are closely proportional to the wave height. Secondly, the maximum stress of nets decreases as the embedded depth increases, while the deformation of nets tends to rise with the increase of pile spacing. At last, several structural optimal patterns are given to improve the safety of pen facilities. This work has laid a solid scientific foundation for designs and optimizations of FPAPs in the future.

Energy flow analysis of grass carp pond system based on Ecopath model

Grass carp (Ctenopharyngodon idellus) is the most productive freshwater fish in China, but its traditional aquaculture model still has problems, such as poor water quality and frequent diseases. We have taken monoculture and 80:20 polyculture grass carp ponds as the research object and used EwE software to build the Ecopath model of two ponds. We analyzed and compared the characteristics of ecological structure and energy flow in two ponds. The result showed the highest effective trophic level in the polyculture pond that was higher than that in the monoculture pond, and fish in polyculture had higher EE values which showed the production of fish in polyculture contributed more to the energy conversion efficiency of the ecosystem. Flows into detritus were the largest component of TST both in the two ponds, which accounted for 49.34% and 50.37%. And the average transfer efficiency in monoculture was 13.07%, while that in polyculture was 15.6%. The ascendency/total development capacity (A/TDC) and overhead/total development capacity (O/TDC) were 0.35 and 0.65 both in the two ponds, respectively, which indicated that both systems had a strong anti-perturbation ability, but the stability could be improved. Finn’s cycling index (FCI) in polyculture was higher and showed that the polyculture pond was more mature and stable. Unused energy of functional groups will flow to detritus, and that in the monoculture pond was higher, the energy of C. idellus that flowed to detritus in monoculture was 48.17% higher than that in polyculture; unused energy of bacteria and phytoplankton were also high. The result showed that polyculture could improve energy utilization, increase transfer efficiency, and raise the stability of the ecosystem. Grass carp ponds still need to be improved in the aspects of mixed species and energy consumption. It is necessary to improve the ecological and economic benefits of grass carp ponds by optimizing the aquaculture structure and adjusting the aquaculture proportion.

An application of maximum entropy model to evaluate the differential effect of cage aquaculture on the distribution of a native and an endemic fish species in Lake Maninjau, Indonesia

Physical cage aquaculture structure can attract native fish species in marine and freshwater ecosystems. Most studies on the effects of cage farms on native fish distribution have been undertaken in marine environments and outside of Asia as the main freshwater cage aquaculture producing region. Many studies have emphasised connections between native fish distribution and feeding time. Previous research also has shown the necessity to use modelling to monitor this effect to reduce data collection costs. Here we analyse the distribution of an endemic fish species, Rasbora maninjau, and a native fish, Gobiopterus sp., associated with tilapia cage aquaculture occurrence using a Maximum Entropy Model (MaxEnt). We find that the application of the MaxEnt model can produce reliable and accurate information on the impacts of cage aquaculture on the native fish species distribution aligning with the more expensive count data method. Our results also suggest that the species-specific interaction between the native fish and cage farms is mainly arising from an interaction between the ecological behaviour of the native fish with dimensions of the environmental condition such as turbidity. Our study therefore highlights the importance for improved appraisal of the ecology of native fish in the cage aquaculture risk assessment.

Variations of Bottom Boundary Layer Turbulence under the Influences of Tidal Currents, Waves, and Raft Aquaculture Structure in a Shallow Bay

High-frequency measurements of tides, waves, and turbulence were made using the bottom-mounted tripod equipped with the Nortek 6-MHz acoustic Doppler velocimetry during 20–23 February 2016 (winter) and 12–26 June 2017 (summer) in Heini Bay, Yellow Sea. The synchro-squeezed wavelet transform was applied for wave-turbulence decomposition, and an iterative procedure was developed to identify the turbulence inertial subrange in the bottom boundary layer. The analysis results reveal the dependency of the inertial subrange on the tidal current and turbulence intensities. The flood-ebb tidal flows are different between the summer and winter seasons, without and with the presence of dense raft aquaculture for kelp, respectively. In summer, the turbulent kinetic energy (TKE), turbulent Reynolds stress (TRS), and dissipation rate (ε) of TKE increase smoothly with the increasing tidal flow magnitude, and ε is approximately in balance with TKE production related to the vertical shear. The presence of heavy kelp aquaculture in winter causes the reduction in flow speeds and TRS, while keeping TKE and ε at high levels.

Marine environmental pollution and offshore aquaculture structure: Evidence from China

The marine environment pollution is becoming an important factor that restricts the sustainable development of mariculture in China. This study takes 10 Chinese coastal provinces (cities) as the study area, based on the rationalization and upgrading dimensions of industrial structure, and innovatively constructs an analytical framework of marine environmental pollution and offshore aquaculture structure to identify the intrinsic relationship between them; and introduces a spatial econometric model to alleviate the estimation bias caused by the public goods attribute of marine environment and improve the reliability of research conclusions. The results show that: (1) The rationalization of the offshore aquaculture structure in China is relatively weak, showing a “concentrated and contiguous” distribution pattern towards the developed aquaculture areas; at the same time, but the differences between regions are expanding; (2) The rationalization and upgrading of the offshore aquaculture structure are affected by the pollution of the marine environment. The degree of upgrading shows different trends; (3) There is a significant spatial adjacency and threshold effect of the negative impact of marine environmental pollution on offshore farming structure. However, due to the limitations of data, the accuracy of our data and the effectiveness of the measurement of industrial structure indicators still need to be improved. Therefore, governmental departments should consider the development of the surrounding areas as well as the pollution emission in the region, and jointly promote the optimization and adjustment of China’s offshore aquaculture structure through the construction of a coordinated management mechanism of marine pollution prevention and treatment.

Underlying Cornerstone of Bunot Lake, Palakpakin Lake, and Calibato Lake: Aquaculture Structure, Road Infrastructure, and Legal Easement

Underlying Cornerstone of Bunot Lake, Palakpakin Lake, and Calibato Lake: Aquaculture Structure, Road Infrastructure, and Legal Easement

Looking from Above the Seven Crater Lakes: Arrangement and Limitation of Aquaculture Structure

Looking from Above the Seven Crater Lakes: Arrangement and Limitation of Aquaculture Structure

Loads on a vessel-shaped fish cage steel structures, nets and connectors considering the effects of diffraction and radiation waves

Vessel-shaped fish cages are a new type of large aquaculture structure consisting of a floating body, steel frames and nets. Unlike in a conventional aquaculture cage, the diffraction and radiation waves induced by the floating body of a vessel-shaped fish cage can induce additional changes to the flow field surrounding the nets. In this paper, the global hydrodynamic responses of the floating body are first calculated in the time domain by the state-space method based on potential theory. The velocity transfer functions around the nets and steel frames induced by the diffraction and radiation waves are attracted, and then their effects on the forces of the nets and steel frames are calculated by Morison equations; thus, the forces/moments of the cross-sections of the main steel structures are calculated by quasi-static method. The forces on the nets and steel frames are then balanced with the motions of the floating body through numerical iterations. Finally, the tensions within the net twines, the loads on the connectors and the cross-sectional forces/moments on the main steel structures are investigated under different waves. It is found that the diffraction and radiation waves introduce a large change in the velocity of the water particle and thus considerably amplify the load effects on the steel structures, nets and connectors.

Spatio-temporal evolution and influencing factors of net carbon sink in marine aquaculture in China

Marine aquaculture not only has considerable economic benefits, but also provides high-quality “decarbonization space” for carbon neutrality, which is of great significance for realizing the goal of “double carbon”. Using the two-stage LMDI (logarithmic mean division index) method, this paper comprehensively analyzes the mechanism of net carbon sink capacity of mariculture in China from five factors: aquaculture structure, aquaculture efficiency, aquaculture scale, competitiveness of shellfish and algae and aquaculture mode. The results show that: 1) the net carbon sink of mariculture in China has increased year by year from 2010 to 2019, with obvious heterogeneous spatial distribution characteristics in three marine economic zone. 2) The improvement of aquaculture efficiency and innovation of aquaculture model contribute the most to the increase of carbon sink, and technological progress plays an increasingly important role. 3) The weak competitiveness of shellfish and algae seriously hinders the growth rate of carbon sink, and is the main reason for the increasing tightening of carbon sink space. 4) Regional heterogeneity analysis shows that the mechanism of increasing carbon sink in marine aquaculture is regionally heterogeneous and resource-dependent. Based on these findings, strategies are proposed to emphasize the ecological values of marine aquaculture, accelerate the technological innovation of deep-sea marine aquaculture, improve the organizational system and the management level, and expand the space for marine carbon sink.

Dynamic Response Analysis of Anchor Piles for Marine Aquaculture under Cyclic Loading

The anchor pile is widely used in marine aquaculture, and its uplift resistance capacity determines the safety performance of the marine aquaculture structure. Cyclic loads such as wind, waves, and currents in the marine environment affect the uplift resistance capacity of anchor piles. By carrying out a cyclic loading model test of anchor piles for marine aquaculture, the influence of loading amplitude, initial tension angle, and other factors on the uplift resistance of anchor piles was investigated. The experimental results showed that with an increase in the loading amplitude, the cumulative displacement and elastic displacement of the anchor pile under vertical and oblique loading increase, and the stiffness of the soil around the anchor piles decreases. The stability of the anchor piles is reduced. When the loading amplitude is the same, with the increase in the initial loading angle, the lateral cumulative displacement of the anchor pile increases. Meanwhile, the vertical cumulative displacement decreases, the stiffness of the soil around the anchor pile decreases, and the stability decreases.

Decoupling Analysis of Net Carbon Emissions and Economic Growth of Marine Aquaculture

Decoupling carbon emissions from economic growth is the key for the sustainable development of developing countries. Based on the panel data of marine aquaculture in China from 2010 to 2019, this paper employs the Tapio decoupling index model to analyze the decoupling characteristics of net carbon emissions and the economic growth of marine aquaculture. The logarithmic average weight decomposition method (LMDI model) and Tapio decoupling effort index model are also introduced to explore the contribution of various areas, provinces, and factors to the decoupling of net carbon emissions and the economic growth of marine aquaculture. Empirical results show that: (1) Net carbon emissions have a decoupling trend from the economic growth of marine aquaculture, but there is a large regional difference. (2) Regarding the degree of decoupling efforts, it is much stronger in the eastern and southern ocean economic zones than that in the northern ocean economic zone. (3) In terms of the decoupling contributions of various factors, carbon emission intensity > aquaculture scale > aquaculture efficiency > aquaculture structure, but there is heterogeneity among the different regions. Among the reasons for the inter-regional differences, carbon emission intensity > aquaculture scale > aquaculture structure > aquaculture efficiency. A further redundancy efficiency analysis explains the source of the differences. On this basis, strategies are proposed to improve the efficiency of marine aquaculture, including the construction of a modern three-dimensional aquaculture system, the improvement of the market-oriented mechanism, and the establishment of a modern marine aquaculture economic system.

Comparison of the 2010 and 2020 ecosystem structures in Xihu Harbor based on the Ecopath model

The Ecopath with Ecosim modeling software was used to construct a Ecopath model for two time periods based on the 2010 and 2020 Xihu Harbor marine ecological environmental survey data. Changes in the Xihu Harbor ecosystem structure over the 10 years were determined, and management recommendations were proposed. The model includes 20 functional groups such as detritus, phytoplankton, Spartina alterniflora, zooplankton, benthic mollusks, Sciaenidae, other planktivorous fish, other piscivorous fish, and sea birds, and cover the Xihu Harbor ecosystem energy flow pathways. The analysis results showed that the types and biomass of important organisms changed during the 10 years; the total resources drastically decreased, fishery resources decreased by almost half, benthic organisms and plankton increased, and the mean ecotrophic efficiency decreased slightly (from 0.493 to 0.472). In 2010, the total energy flow from primary producers to each trophic level was 1406 t/km2·a, and the total energy flow from detritus to each trophic level was 1559 t/km2·a. In 2020, the total energy flow from primary producers to each trophic level was 2628 t/km2·a, and the total energy flow from detritus to each trophic level was 2751 t/km2·a. The energy input from primary producers and detritus in the Xihu Harbor ecosystem increased significantly. This was because macroalgae cultivation and expansion of S. alterniflora increased primary productivity as well as the expansion of the scale of mariculture, which increased detritus biomass and supported a high amount of energy flow through the system. The main reasons for changes in the Xihu Harbor ecosystem structure were S. alterniflora invasion, changes in aquaculture structure, and the decline in fishery resources. We propose targeted marine management measures, including using local salt marsh plants to replace S. alterniflora to maintain high primary productivity, continuing optimization to improve mariculture structure, and strengthening the seedling release of marine organisms.

Effects of nutrient-rich submarine groundwater discharge on marine aquaculture: A case in Lianjiang, East China Sea

Submarine groundwater discharge (SGD) and associated nutrient have long been received insufficient attention in the aquaculture areas of Lianjiang, East China Sea. In this study, we used 224Ra mass balance model to evaluate the importance of SGD in the aquaculture areas of Lianjiang in different seasons. The results showed that SGD fluxes were 0.14 ± 0.070 m3 m−2 d−1 in July and 0.077 ± 0.040 m3 m−2 d−1 in October 2019, which corresponded to approximately 22% and 32% of the river discharge, respectively. Nevertheless, the dissolved inorganic nitrogen (DIN) and phosphorus (DIP) fluxes contributed by SGD over total nutrient inputs were approximately 58% and 73%, respectively in July, 11% and 33%, respectively in October 2019. The ratio of DIN to DIP in seawater was slightly higher than that derived from SGD in July and significantly lower than that derived from the river and SGD in October, which was prone to profound modulated by shellfish (e.g., clam Ruditapes philippinarum and Sinonovacula constricta) and nori (e.g., Pyropia haitanensis) that selectively acquire nitrogen and phosphorous, suggesting that SGD could affect the nutrient structure and aquaculture activities in Lianjiang. Moreover, the new primary production via SGD yielded (2.47 ± 1.32) × 103 mg C m−2 d−1 in July and (3.52 ± 1.76) × 102 mg C m−2 d−1 in October 2019, which were approximately 8–25% and 10–31% of the production in the entire study area. These meaningful discoveries indicated that SGD and associated nutrient are the predominant regulator of nutrient and aquaculture structure under significant seasonal differences.

A numerical framework for modelling the dynamics of open ocean aquaculture structures in viscous fluids

This paper presents a complete numerical framework for modelling open ocean aquaculture structures in waves and current using Computational Fluid Dynamics (CFD). A structural dynamics model is incorporated to account for the motions and deformations of the net. It is based on the lumped mass method, a non-linear material law and implicit time step advancing. The presence of the porous net is considered in the momentum equations of the fluid using a forcing term based on Lagrangian-Eulerian coupling and the acting forces on the net. The proposed framework is suitable for simulating the interaction of nets of arbitrary geometry and under large motion with fluids including complex free surfaces. This is in contrast to existing models which either neglect important non-linearities, the physical interaction with the fluid or are limited to certain net geometries. In addition, the fluid-structure interaction of floating objects with mooring lines, nets and fluid is accounted for in the model. A new floating algorithm is presented for the interaction of the fluid and the rigid structure. It is based on a continuous direct forcing immersed boundary method and a level set representation of the object in the Eulerian fluid domain. This effectively avoids computationally expensive reconstruction processes of existing approaches and enables the application to large three-dimensional structures. The complete numerical framework is first validated against existing measurements for forces on rigid and flexible nets, net deformations and moored-floating structures with and without a net in waves. Then, a semi-submersible and a mobile floating open ocean aquaculture structure are investigated, and the possibilities of the numerical approach are highlighted.