Net Cage Aquaculture Research Articles

Experimental study on hydrodynamic performance of the semi-submersible vessel-shaped fish cage

Deep-sea net cages play a vital role in expanding offshore farming in modern marine fisheries. In this paper, a model-scale 1:40 tank experiment was conducted for a vessel-shaped truss-structured single-point mooring deep-sea aquaculture net cage. The study focused on the hydrodynamic characteristics, including the effect of current, wave, and net on the mooring force, heave, and pitch motion behaviors. Experimental results indicate that the mooring force increases with the current velocity, draught of the cage, and wave height, but decreases with the wave period increase. Both heave and pitch movements amplitudes increase with wave height. While heave motion amplitude initially declines and then ascends with wave periods, pitch motion shows the opposite pattern. Besides the net has an obvious damping effect on the pitch motion. These results can provide data support for the design and offshore installation of vessel-shaped truss-structured net cages in the future.

Correction: Body size estimation method for seasonally growing farmed yellowtail Seriola quinqueradiata in an aquaculture net cage using a stereo camera

Correction: Body size estimation method for seasonally growing farmed yellowtail Seriola quinqueradiata in an aquaculture net cage using a stereo camera

UAV Control Based on Pattern Recognition in Aquaculture Application

This study proposes a drone application for the net cage aquaculture industry. A visual control structure is applied to the drone to obtain water-quality information surrounding the net cages. This study integrates a hexacopter, camera, onboard computer, flight control board, servo motor, and global positioning system’s auto-cruise function to adjust the drone position and control the servo motor retractable sensor to reach the desired target at an accurate location. In object identification, a deep learning neural network is used to identify the net cages. An onboard computer calculates the horizontal distance between the drone and the net cage. A “You only look once” (YOLO) neural network is used to detect the net cage images. Considering the hardware calculation speed and ability, an onboard computer is applied to process the flight control board and control the drone. In the mission, an aerial camera detects targets (net cage) and provides visual information to the drone for the target approaching control process. After executing the water-quality measurement, the drone will end the mission and return to the base. This study modifies the architecture of YOLO, compares it with the original model, and then finds a proper architecture for this mission. This study aims to assist cage aquaculture operators by using drones to measure water quality, which can reduce aquaculture’s labor costs.

Trophic state assessment of marine ecosystems used for floating net cage aquaculture: a case study in Pegametan Bay, North Bali, Indonesia

Trophic state assessment of marine ecosystems used for floating net cage aquaculture: a case study in Pegametan Bay, North Bali, Indonesia

Body size estimation method for seasonally growing farmed yellowtail Seriola quinqueradiata in an aquaculture net cage using a stereo camera

Body size estimation method for seasonally growing farmed yellowtail Seriola quinqueradiata in an aquaculture net cage using a stereo camera

Effect of light exposure on circadian rhythm in theront excystment in Cryptocaryon irritans

We examined the effects of light exposure on the theront excystment circadian rhythm in Cryptocaryon irritans using a newly invented apparatus, which enabled us to examine the excystment rhythms of theronts from tomonts with low labor. Using the apparatus, we examined the timings of theront excystment from tomonts exposed directly to light and from tomonts exposed to light-exposed seawater by counting the number of excysted theronts. We found that the theront excystment time changed only when tomonts were directly exposed to light, indicating that light reception is essential for circadian rhythm entrainment. When tomonts were exposed to light only once for 12 h, either on Day 1, Day 2, or Day 3 after leaving host and being encysted, the circadian rhythm was entrained according to the photoperiod given on tomonts. Tomonts exposed to a low light (1 lx) with 12L:12D photoperiod daily showed a circadian rhythm similar to that in tomonts exposed to an intense light (500 lx) under the same photoperiod. When tomonts were incubated at 22 °C, 25 °C, or 28 °C under the same photoperiod, almost the same circadian rhythm was developed, suggesting temperature has little effect on the circadian rhythm entrainment between the range, even though the date of excystment was delayed in lower temperatures. These results suggest the circadian rhythm of theront excystment can be entrained in tomonts on the seabed of inner bays where net–cage aquaculture is conducted, and be involved in the outbreaks of cryptocaryoniasis there.

Hydrodynamic Analysis of a Multi-Pile-Supported Offshore Wind Turbine Integrated with an Aquaculture Cage

The integrated development of offshore wind power and marine aquaculture is becoming increasingly important. However, the impact mechanism of integrating a net cage on the dynamic characteristics of offshore wind turbines remains unclear. This paper presents a design scheme for a multi-pile-supported offshore wind turbine integrated with an aquaculture net cage and conducts a preliminary theoretical analysis of the influence of an additional net cage on the wind turbine. The analysis reveals that the primary effect is an increase in hydrodynamic loads on the wind turbine foundation, while the structural frequency of the wind turbine remains largely unaffected. Furthermore, computational fluid dynamics (CFD) numerical models, whose accuracy is verified by physical experiments, are utilized to compare the hydrodynamic characteristics of the offshore wind turbine foundation with and without the net cage, considering different net solidities. The simulations identify significant changes in the flow field surrounding the foundation due to the presence of the net cage, resulting in a considerable increase in the overall hydrodynamic load on the foundation. Moreover, the mutual interference between the netting and the foundation amplifies their respective hydrodynamic loads and concentrates these loads at the upstream section of the structure. The maximum increase in hydrodynamic load for a single pile reaches 6.32 times its original value, posing significant risks to the structure. Finally, a preliminary feasibility analysis of the scheme was conducted. The results presented in this article can serve as a theoretical basis for the design of such innovative structures.

Physiological stress responses of European seabass Dicentrarchus labrax related to changing operations of floating net cages in intensive farming conditions at the Moroccan M'diq bay.

The present study purposed to quantify and compare in-situ the primary and secondary physiological stress responses, related to the operation of floating net-cages changing, in both sub-adults (523 days post hatching) and adults (916 dph) European sea bass Dicentrarchus labrax, under intensive farming conditions in the Moroccan M'diq Bay. Levels of cortisol, glucose, total cholesterol, total protein and lactate, as well as the percentage of hematocrit were measured before and after stress. The results showed significantly elevated levels of cortisol and blood glucose in both age groups, while total cholesterol and protein levels were unaffected. In fact, blood lactate was significantly reduced in sub-adults, while in adults this parameter was not affected by the operation. However, the hematocrit percentages measured after the operation were significantly higher than those found before the operation in both groups of fish, which is linked to the increased rate of oxygen renewal by the new net cages and the lower water temperature inside the cages. With regard to the age-specific response during this essential operation - before and after the operation - plasma cortisol, blood glucose and lactate concentrations, as well as plasma total protein levels, were significantly higher in sub-adults than in adults. It is concluded that aquaculture practices such as changing the aquaculture net-cage could have repercussions in terms of the classic physiological responses to stress in D. labrax. This article is protected by copyright. All rights reserved.

Preliminary Results on the Antifouling Potential of Copper Wire and Dyneema® Fiber Combined Twines for Aquaculture Net Cages

Antifouling management for aquaculture cage nets has developed over the years to reduce the costs of cleaning the nets and minimize the damages caused to the nets by the encrustation of benthic organisms. There have been various approaches to this end such as using toxic paints (TBT-SPC, etc.) and nanomaterial coatings, mechanical cleaning using brushes, and constructing the net using copper alloys instead of nylon (or other) material, etc. We designed and constructed experimental fish farm nets substituting Dyneema® fibers with uncoated copper wire 0.15-0.2 mm in diameter by 5%, 10%, 20%, and 40% and deployed them in a commercial operating fish farm for almost 7 months. We examined their antifouling performance based on the percentage of mesh openness remaining by the end of the experimental period. The results showed that the antifouling performance increased with copper substitution level and peaked at a level of 29.79% and maximum mesh openness at 46.5%.

Towards a holistic digital twin solution for real-time monitoring of aquaculture net cage systems

Digital twins and relevant concepts are being applied in a wide variety of ways, and they are of most use when an actual real-world physical system or process (a physical twin) is changing over time and when measurement data correlated with this change can be captured. In this work, a digital twin model was implemented for real-time monitoring of aquaculture net cage systems, which is notoriously challenging because of several difficult-to-measure properties, such as forces on and deformation of the flexible netting structures, waves and flow field alterations around the cage and complex stiffness behaviour of the mooring elements made by fibre ropes. These properties were set to be adaptable according to the resultant outputs, such as cage responses and mooring loads that were continuously compared with the measurement data obtained from remote monitoring sensors. In this way, real-time sensor data were assimilated into the numerical simulation model for representing the actual net cage system. No dedicated sensors were used for fish monitoring, but the fish behavioural responses to current, wave and cage deformation were modelled according to relevant field observational data. A wireless sensor network has also been tested for the digital twin implementation, which was found to be suitable for practical uses in fish farms.

Ecological, Social, Economic Sustainability Policies and Fish Cultivation in Reservoir Waters

Dams have a very large ability to develop fish culture, then from that the development of fish culture grows rapidly. This rapid progress greatly resulted in a reduction in water quality, good for the life and progress of fish and their food-living creatures. This dam is also used for capturing fisheries, floating net cage aquaculture (KJA), transportation, and tourism. This research is literary research from several posts that study articles on the status of the sustainability of dams and the sustainability of KJA aquaculture in multidimensional sustainability (environmental, economic, and social sciences). Based on the results of policy research on the sustainability of environmental, social, and economic science and fish farming in dam waters, the sustainability of dams as well as the sustainability of KJA cultivation are very supportive of one another. Prolonged management of the dam will help the sustainability of KJA cultivation.

Estimation of Water Carrying Capacity for Floating Net Cage Cultivation Activities in Pekalongan Coastal Waters

Floating cage fish farming is an aquaculture activity that is mostly carried out on the coast of Pekalongan. The purpose of this study was to estimate the carrying capacity of Pekalongan coastal waters as a floating net cage aquaculture activity zone. The research method used is descriptive qualitative and quantitative descriptive by calculating the indicators of Trophic Status Index (TSI), phosphorus, feed conversion ratio, and the carrying capacity level of the waters. The results showed that chlorophyll-a values ranged from 6.44-8.24 ꭒg/L, total phosphorus 12.44-14.80 ꭒg/L, feed conversion ratio 1.10-1.25, TSI (Trophic Status Index) values 48.2-54.6, harvested biomass 120-157 kg/ floating net cages (KJA). The carrying capacity of the waters for KJA cultivation is 145.43 tons of fish/year, and the number of existing KJA for cultivation is 110 KJA. The conclusion from the results of this study is that the carrying capacity on Pekalongan coastal waters when used as a floating net cage aquaculture activity zone is estimated to be able to accommodate approximately 145.43 tons of fish/year or the equivalent of 121 KJA. Currently, there are 110 KJA plots in the Jeruksari coastal waters, which means that the maximum carrying capacity of the waters that can be used for KJA cultivation is 11 KJA.

Robust adaptive backstepping DP control of ROVs

Dynamic positioning is an important control feature for an underwater remotely operated vehicle. This paper presents a nonlinear dynamic positioning controller suited for application to vehicles with model uncertainties, operating in environments with unpredictable disturbances, such as an aquaculture net cage. The proposed controller combines the backstepping approach with an adaptation term to ensure robustness. Using Lyapunov theory and Matrosov’s theorem the origin of the closed-loop system is proven to be: (i) globally asymptotically stable when assuming persistency of excitation, and (ii) stable and bounded, with the true position converging to the desired position if there is no persistency of excitation. This paper also presents results from simulations where the proposed controller is contextualized and compared to similar controllers, showing promising results. Finally, as the main result of the manuscript that demonstrates the effectiveness of the proposed control law, an extensive field trial campaign is conducted at a full-scale aquaculture site using an industrial ROV where the proposed controller is successfully tested under realistic operational conditions.

Digital twin for rapid damage detection of a fixed net panel in the sea

The fishing net is the most important component of aquaculture net cages. Once damaged, it can cause substantial economic losses and ecological problems to the aquaculture industry. To avoid these subsequent issues caused by the damage to the fishing net, seeking a computerized, labor-saving approach and detecting damage in real time becomes the primary task of this paper. Inspired by recent development of the artificial neural networks and machine learning, this study proposes a fast and accurate approach for fishing net damage detection based on digital twin. Firstly, time-domain numerical simulations of the fishing net are conducted in a series of wave and current conditions to develop the artificial neural network-based digital twin. Then, the significant wave height, the spectral peak period, and tensions of vertical and horizontal ropes are used as input variables during the artificial neural network training; the intact and damaged states of the fishing net are considered outputs. Alongside this, the back-propagation learning algorithm is used for training to maximize damage detection performance. The results highlight that the digital twin model can effectively identify the fishing net damage using the sensor data, and the accuracy of the damage detection reaches above 93%. When the damage occurs at different net positions, the prediction accuracies of the artificial neural network model for training and testing sets are 93.97% and 93.00%, respectively. Regarding different wave-current directions, the prediction accuracies of the artificial neural network model are 99.87 % and 99.34 % for training and testing sets. Moreover, the developed digital twin can accurately detect the damage of the net even sea conditions and sensor data are not included in the training. The digital twin model proposed in the present study can potentially be used for damage detection in other aquaculture components and structures.

Recognition and statistical analysis of coastal marine aquacultural cages based on R3Det single-stage detector: A case study of Fujian Province, China

Fujian Province, located in the southeastern coast of China, has a highly developed coastal marine net cage aquaculture industry. The scale and density of marine aquaculture, especially net cages aquaculture, in China are increasing, which has seriously affected coastal and nearshore environments. Thus, methods for accurately obtaining the area and density of aquaculture net cages hold great significance. Because of the scattered distribution of net cage aquaculture areas, it is difficult to obtain an accurate net cage aquaculture area with traditional remote-sensing extraction methods. Therefore, this paper proposes a method for accurately identifying of the area of aquaculture net cages by combining R3Det single-stage detector and fishnet segmentation technology. A constructed sensing net cage dataset was used for model training and a fishing net segmentation technology was used to segment the remote-sensing image into R3Det testable image. The experimental results showed that the extraction accuracy of this method for round and square net cages was 92.65% and 98.06%, respectively, and the extraction accuracy of the actual net cage culture area was 97.24%. We concluded that the total area of net cage aquaculture in Fujian Province in 2019–2020 was 4363.58 ha, mainly in square net cages. The area of aquaculture was greater in the northern and southern parts of the province and less in the middle. The density of aquaculture was high in the south and low in the north. Compared with traditional remote-sensing extraction methods and neural networks, this solution reduced the impact of similar features on the classification target, realized the application of high-precision, large-area remote-sensing images on the R3Det single-stage detector, and improved the recognition accuracy and the robustness of the model.

Assessment of Sea-Area Benchmark Pricing: Using Chinese Aquaculture to Evaluate and Revise the Price Structure of Resources

Kong, H.; Shen, J.; Zhao, Y., and Sun, Q., 2022. Assessment of sea-area benchmark pricing: Using Chinese aquaculture to evaluate and revise the price structure of resources. Journal of Coastal Research, 38(5), 925–936. Coconut Creek (Florida), ISSN 0749-0208. China has implemented a system of paid use of sea areas and has in recent years promoted their market-oriented allocation to ameliorate the efficiency and to realize their intensive and economical use. Estimations of the sea-area benchmark price can reveal the differences in sea areas, quality, and efficiency. This study introduces a framework to assess the benchmark price of the sea areas, applied to open aquaculture in Lianjiang County (Fujian Province, China). The assessment results show that the sea area used for bottom-sowing aquaculture in Lianjiang County was classified as Grade 2, whereas the sea area used for raft aquaculture and net cage aquaculture was classified as Grade 4. Upon comprehensive consideration of the theoretical value and the actual demand for sea-area management, the benchmark price of three types of open aquaculture sea areas is evaluated. The benchmark prices for bottom-sowing culture sea areas were found to be RMB 65–117/mu/year; for raft culture sea areas, they were RMB 20–252/mu/year; and for net cage culture, sea areas were RMB 100–800/mu/year. Overall, this study constructed a revised system of sea-area benchmark pricing, considering the natural conditions of the sea area, policy factors, transportation and infrastructure, culture conditions, and development degree. These results could be used as the guiding prices of the government to transfer sea-area resources and could ensure the realization of the economic interests of the government as owner of the sea area. Furthermore, this approach can provide a novel way to evaluate sea-area prices in other coastal areas.

Alternative Livelihood Potential of Fishermen Households in The Liukang Tangaya Aquatic Conservation Area, Pangkajene Islands Regency

The potential and development of alternative livelihoods for fishermen households in marine conservation areas must be relevant to or refer to the context of contextual technical considerations (locality), and not a deduction or bottom-up policies derivation so that they can grow and develop (facilitating) local fishermen's households in production activities that are complementary to increasing the spirit of the locality, community harmonious with natural resoureces and welfare through the opening of new economic spaces that can be accessed and controlled by the local community themselves. This type of research is qualitative with a case study approach. Data was collected through direct observation and in-depth interviews with some informants. There are 30 fisherman’s household which is used as primary data source informants. Qualitative analysis based on technical variables, namely community interest, availability of local raw materials/natural resources, availability of labor and market opportunities through content analysis from compilation of interview results through snowball technique with reference to triangulation principle. While quantitative data analysis is carried out with business feasibility indicators for new alternative types of livelihoods that can be applied to fishermen households, namely B/C Ratio indicators, Return Of Investment (ROI), and Payback Period (PP). Research result show that based on the analysis of technical variables, the potential alternative livelihoods carried out by fishermen households are seaweed aquaculture, floating net cage aquaculture, processed fishery products, coconut and household scale chicken and duck farming. The B/C ratio value of these businesses is > 1 with very profitable criteria to do.

Numerical study on the flow environment for a novel design of net cage with a shielding device

As aquaculture moves from inshore to the deep sea, developing a comfortable swimming environment for the farmed fish to cope with the strong current in the open sea becomes vitally imperative. This study designs a novel net cage with a shielding device to provide a sheltered area for the farmed fish at extreme ambient current speeds. Considering the time-consuming and substantial economic loss caused by the destruction of the net cage in situ measurements, a numerical method based on computational fluid dynamics (CFD) modeling is employed to evaluate the flow field of the net cage. Three characterized parameters, namely the height of the middle plane nets, the inclined angle of plane nets, and the net solidity, are used to estimate their influences on the flow field of a net cage and the drag force loaded on it. The results highlight that the height variation of the middle-plane nets has little effect on the flow field and the drag force. Nevertheless, the increased inclined angle of plane nets and net solidity leads to a dramatic fluctuation regarding the current velocity distribution and the drag force. In particular, the increase of the inclined angle for the plane nets causes a noticeable increase in the cage volume. With this understanding, further aquaculture net cages can potentially be designed to better withstand the ocean's rigors and maintain the aquaculture industry's sustainability.

Potensi Harmful Algae Bloom (HAB) di Keramba Jaring Apung Perairan Desa Sumberkima Kecamatan Gerokgak, Kabupaten Buleleng

Sumberkima Village is one of the villages in Gerokgak sub-district that has the most floating net cage cultivation in Buleleng regency. The development of fish farming activities with floating net cage techniques had an impact on the waters. The leftover feed that is not consumed, and the metabolic wastes produced by aquaculture increased the fertility of the waters so that it is feared that phytoplankton are potentially causing the Harmful Algae Bloom (HAB) phenomenon in the floating net cage aquaculture area of Sumberkima village which can have an impact on water quality, aquatic biota and cultivator’s income. This study aimed to identify the genus phytoplankton that has the potential to cause Harmful Algae Bloom (HAB) and the abundance of phytoplankton that has the potential to cause the Harmful Algae Bloom (HAB) phenomenon. This research was conducted in February 2019 at the floating net cage in Sumberkima village, Gerokgak sub-district, Buleleng regency. The study was spread over 10 points of floating net cages determined by purposive random sampling to represent floating net cages in Sumberkima village. Data were analyzed descriptively with phytoplankton abundance calculation using APHA (2005) method. From the research that has been done, it was found that the type of phytoplankton suspected to have HAB potential was found in 2 class groups namely Dinophyceae with a percentage of 15% consisting of: Prorocentrum, Dinophysis, Alexandrium and Peridinium then Bacillariophyceae with a percentage of 85% as many as 7 genera include: Thalassiosira, Pseudonitzschia, Biddulphia, Nitzschia, Skeletonema, Chaetoceros and Ceratium.

Analysis of the Competitiveness of Floating Net Cage Aquaculture in Indonesia

The purpose of this study is to analyze the competitiveness profile of floating net cage aquaculture in Indonesia. The research was conducted in February – June 2021 at the Directorate General of Aquaculture, Ministry of Marine Affairs and Fisheries of the Republic of Indonesia. The data collection method used in this study is the literature survey method. Primary data in the form of questionnaires with expert judgment respondents as many as 13 people consisting of 11 Lecturers of the Faculty of Fisheries and Marine Sciences, Padjadjaran University, and 2 employees of the Directorate General of Aquaculture, Ministry of Marine Affairs and Fisheries of the Republic of Indonesia regarding the proportion of competitiveness of floating net cage aquaculture fisheries. Secondary data in the form of statistical data on floating net cage aquaculture in 2017 was obtained from the Directorate General of Aquaculture, Ministry of Marine Affairs and Fisheries of the Republic of Indonesia. Data analysis was carried out by using quantitative descriptive analysis. The results showed that Central Java Province which was supported by facilities and infrastructure variables, West Java Province which was supported by human resources and production variables, and North Sulawesi Province which was supported by science and technology variables were in the top three with very high competitiveness category, while the Riau Islands Province and the Bangka Belitung Islands Province are in the bottom two ranks with the low competitiveness category.