Net Cage Aquaculture Research Articles

Fluid-Structure Interaction (FSI) Modelling of Aquaculture Net Cage

The number of good sites in less exposed locations for aquaculture farming is limited. Trends are now that the fish cages are increasing in both width and depth, as well as more weather-exposed locations, are taken into use. As the net cages continue to increase in size, so does the material costs. The design of the sea cages should be modified for safe and reliable use in remote offshore locations. Fish farms located in more exposed areas will be subject to more energetic waves and stronger currents, which will cause large net deformations. This is a challenge as fish welfare depends on a certain minimum volume within the net cage. Changing and maintaining net cages are some of the main expenses for fish farms. If the lifetime of the net cages is extended by introducing stronger, longer lasting materials, the overall costs of the nets will be reduced. The traditional nets are produced in nylon, while the promising solid PET-wire has been introduced to the aquaculture industry. In this paper, we introduce polyurethane to the aquaculture net cages, which will be studied together with nylon and PET-wire. The study is carried out using fluid-structure interaction (FSI) simulation, computational fluid dynamics (CFD) weakly coupled with structure mechanics (FEM). ANSYS® software is employed in the study. We will look at the materials that show the most promising results for aquaculture purposes.

Identification and quantification of farmed red sea bream escapees from a large aquaculture area in Japan using microsatellite DNA markers

A large number of farmed red sea bream (Pagrus major) and their gametes have escaped and dispersed into the wild from net-cage aquaculture since the advent of the technology in the mid-20th century. These escapees have likely been recruited into wild populations, affecting their genetic diversity. In this study, we used assignment methods with microsatellite markers to assess the frequency of escapee farmed red sea bream within the wild populations in a major aquaculture production region (UWJ) and in two regions with relatively lower production (IWG and SIJ) in Ehime Prefecture, Japan. The frequency of escapees in UWJ ranged from 14.1% to 30.2%, as shown by three methods of assignment. Escapees were frequently identified among specimens caught by angling (ranging from 26.7% to 46.7%), suggesting that they stay in the same area even after escape or are less cautious than wild individuals. No escapee was found in IWG and SIJ, areas with less extensive aquaculture. Some wild-caught fish appeared to have hybridized with farmed fish, as indicated by the threshold of membership coefficients obtained by simulation. These results clearly indicate that large numbers of farmed individuals have escaped from UWJ, a major aquaculture area, since the inception of red sea bream farming in Japan. Genetic reshuffle has possibly occurred following hybridization of wild and farmed individuals.

Environmental quality assessment using microalgae structures adjacent fish faming at Setoko Island, Batam City, Kepulaun Riau Province

Along with the increasing challenges that come with the demand for national and international fisheries’ products and the potential emergence of various environmental concerns, various efforts have been made to increase production capacity through extensification and intensification programs. This study aimed to assess the environmental quality and the level of disturbance in the floating net cage aquaculture area based on the microalgae community structure. The research was conducted from August to October 2017 at the water ecosystem used for aquaculture at Setoko Island, Batam City, Kepulauan Riau Province. Purposive random sampling was used by determining 3 sampling stations with three replicates. Data was analyzed using saprobic, Shanon-Wiener (H’) diversity, abundance and domination indices. The result showed that 13 genus microalgae (bawal fish fish farming), 9 genus (fish farming kakap) and 11 genus of microalgae (kerapu fish farming ) consisting of Chlorophyta, Chyanophyta Chrysophyta and Dinophyta were recorded. The value of H’ index at the farming area ranged from 0.73 to 1.5. Microalgae abundance was dominated by Phacus sp, Coscinodiscus sp, Climacosphenia sp and Spirogyra sp. Based on the saprobic index, the farm area has an index value of 1.92, thus it can be refferred to as the oligo/β-meso-saprobic phase, indicating light disturbance by organic enrichment.

Artisanal fisheries of the Itaparica reservoir, São Francisco River, Brazil: socioeconomic profile, environmental dynamics, and management recommendations

Currently, artisanal fisheries in fresh water reservoirs have been losing ground to commercial fish farming and a great deal of fishery resources are being threatened by human interventions, such as reservoir management and increasing net-cage aquaculture. This study aims to understand the impacts of environmental changes on fishery resources and analyse the migratory fish breeding season as a missing link for fishery management in the semi-arid area of the Sao Francisco River Basin. Among the 870 fishermen operating in the Pernambuco part of the Itaparica Reservoir, 10% were interviewed and affirmed that fish stocks have been compromised due to the closed fishing period’s incoherence, exotic species insertion, and changes to the river flow caused by reservoir construction and operation. A significant correlation was observed between the Reproductive Activity Index (RAI) and precipitation (p = 0.745) as well as between the RAI and the river’s flow (p = −0.909). This shows how important it is to consider both the semi-arid climate setting and reservoir operation in determining the closed period which should safeguard fish reproduction. Monitoring the fish reproduction period and research on the reproductive biology of native fish species is needed in the Sao Francisco River Basin’s different stretches in order to guarantee valuable fish stocks and fisheries maintenance. Integrated action between the fish resource users, civil society, and federal bodies/agencies is essential in order to mitigate impacts and improve fish production systems, not only in Brazil, but in other regions experiencing a similar scenario.

Development of a numerical model for fluid-structure interaction analysis of flow through and around an aquaculture net cage

In the present work, we developed a numerical model for fluid-structure interaction analysis of flow through and around an aquaculture net cage. The numerical model is based on the coupling between the porous media model and the lumped mass structural model. A novel interface was implemented to ensure efficient data exchange and element mapping between the fluid and structural solver via random-access memory. The main idea is to apply a static mesh in the fluid model, in case that large deformation of the net structure reduces the quality of the mesh. Then the geometry of the net cage was approximated by a set of dynamic porous zones, where the grid cells were updated at every iteration based on the transferred nodal positions from the structural model. A time stepping procedure was introduced, so the solver is applicable in both steady and unsteady conditions. In order to reduce the computational effort, sub-cycling was applied for the structural solver within each time step, based on the quasi-steady state assumption. The numerical model was validated against experiments in both steady and unsteady conditions. In general, the agreement is satisfactory.

Evaluation of Applications Floating Net Cage Aquaculture Systems Integrated Multi Trophic Aquaculture (IMTA) and Monoculture an Based Growth Rate Silver Pompano (Trachinotus blochii, Lacepede)

Evaluation of Applications Floating Net Cage Aquaculture Systems <i>Integrated Multi Trophic Aquaculture</i> (IMTA) and Monoculture an Based Growth Rate Silver Pompano (<i>Trachinotus blochii</i>, Lacepede)

Simulations of nutrient emissions from a net cage aquaculture system in a Brazilian bay.

Hydrodynamics and transport simulations were conducted with the modeling software TELEMAC-2D on Icó-Mandantes bay, a branch of the Itaparica reservoir. The bay has a maximal operational water level amplitude of 5 m and is suffering from eutrophication and algae bloom. Therefore, we investigated low and high water level scenarios with two different high resolution meshes, with the purpose to deeper understand their impact on transport of substances and to improve the watershed management. In particular, nutrient emissions from a hypothetical net cage aquaculture system located in the bay were investigated on half-year cycles. We observed a relevant impact on water quality for a tilapia production of 130 t y(-1); i.e. after 6 months' simulation we obtained around 8 μgP L(-1) and 6 μgP L(-1) at the source of emissions, for low and high water scenarios, respectively.

一様流における養殖生簀用平面網地の流体力特性について

一様流における養殖生簀用平面網地の流体力特性について

Experimental study of an aquaculture net cage in waves and current

Model experiments of a floating fish cage subjected to waves and current have been performed. The objective was to study the dynamic behaviour of the fish cage model in waves and current. The fish cage model was composed of a model net, a flexible floating collar of the circular plastic type and a weight system. It was found that there are many wave periods in which cancellation of the wave-induced forces on the model occur. These cancellation wave periods are within the range of dimensioning wave periods commonly used for testing of fish farm structures and hence are important to be aware of. Large deformations of the net under realistic wave and current conditions were observed, where contact between the net and other parts of the structure were identified. This may cause damages to the net due to abrasion.

Carrying capacity limits of net cage aquaculture in brazilian reservoirs

Finfish aquaculture in net cages is widely used in Brazilian reservoirs, mainlyfor tilapia production. There is a large and increasing potential for productionin the Sao Francisco river basin, and particularly the Itaparica reservoir. Tilapiaproduction amounts to 24,000 t y-1, with a licensed amount of 43,267 t y-1.This intensive fish production in net cages is responsible for a significantbiological oxygen demand, and phosphorus and nitrogen load on the reservoir,which promotes eutrophication. Particulate organic matter released from thenet cages accumulates beneath the net cages, and a minimum water depthbeneath the net cages of 10 m is required to limit the sediment increase toa few millimetres per year. Modeling of Ico-Mandantes bay has identified areduced water exchange within the bay. Modeling of the effect of net cageaquaculture within the Ico-Mandantes bay points out clearly the significantincrease in dissolved phosphorus and the accumulation inside the bay area.The carrying capacity of the reservoir was determined using the P loadmodel, with a critical P concentration based on the phosphorus use efficiency.The critical P concentration amounts 25 μg L-1, and the critical P load of thereservoir amounts 2.84 g m-2 y-1; the actual load is already 3.30 g m-2 y-1,such the reservoir is already overcharged by nutrients. A sustainable “blue”aquaculture must be implemented based on use of advanced systems, speciesselection, fish feed, and linked production systems.

Experimental and numerical study of an aquaculture net cage with floater in waves and current

The mooring loads on an aquaculture net cage in current and waves are investigated by dedicated model tests and numerical simulations. The main purpose is to investigate which physical effects are dominant for mooring loads, and in this respect, to investigate the validity of different rational hydrodynamic load models. Also structural and numerical aspects are investigated. The model tests are performed to provide benchmark data, while the numerical model is used to study the effect and sensitivity of different load models and parameters.Compared to a realistic aquaculture plant, the total system is simplified to reduce the complexity. The system does, however, include all the four main components of an aquaculture plant: net cage, floater, sinker weights and moorings. The net cage is bottomless, flexible and circular. It is attached to a circular, elastic floater at the top and has 16 sinker weights at the bottom. The system is nearly linearly moored with four crow feet mooring lines.The loads are measured in the four mooring lines. A systematic variation of current only, wave only as well as combined current and wave conditions is carried out. The numerical simulation results are first benchmarked towards the experimental data. The mean loads in general dominate over the dynamic part of the loads in combined current and waves, and they significantly increase in long and steep waves, relative to current only. Next, a sensitivity study is carried out. A rigid floater significantly alters the loads in the mooring lines compared to a realistic, elastic floater. The theoretical model for the wave matters. The mooring loads are rather insensitive to a majority of the parameters and models, in particular: frequency dependent added mass of the floater and nonlinear restoring loads. It seems not to be necessary to represent the net cage with a very fine numerical mesh.

Numerical simulation of forces and motion deformation of deep-water net cages in waves and currents

This study is aimed to discuss the effects of waves combined with currents on forces and motion deformation of deep-water net cages,and provides a strong reference to risk assessment for net-cage aquaculture with severe marine conditions.The set value of wave and current elements were as follows:wave heights H=4-6 m,wave periods T=6.0-8.6s,current velocities U=0.3-0.9 m/s.With a numerical model previously validated by physical model tests,the mooring line forces,the wave-current forces,the volume reduction rate and the floating-collar pitches of the deep-water net cage were calculated.The simulated results indicated that the mooring line force,the wave-current force and the volume reduction rate were all in direct proportion to wave height as well as current velocity,but less related to wave period.Furthermore,the wave-current force on the cage was approximately equal to the sum of force on each mooring line on wave-side.The volume reduction rate reached 47%-56% for the cage caused by the conditions of wave height of 4 6 m and current velocity of 0.75m/s,which showed serious cage deformation.Therefore,we concluded that farming sites should not be placed in sea areas where current speed exceeded 0.75 m/s.The calculated results also showed that the influence of wave period on volume reduction rate was slight,while significant on the floating-collar pitch.The floating-collar pitch would decrease as wave period increasing at constant wave height and current velocity.

허베이스피리트호 유류오염피해배상에서 수하식 및 가두리식 양식어업의 피해정도사정 사례

Recently the Korean court accepts two typies of fisheries damages caused by oil pollution.. One is the direct loss of fisheries production originated from pollution of oil spillover. The other is the indirect loss of fisheries production originated from governmental measure of restricting fishing activities because of safety of marine product of oil spillover areas. The paper tries to suggest the appropriated measure of oil pollution damages of hanging and floating netcage aquaculture fisheries using the court judgement for responsibility restriction on Herbei Spirit Case. The paper tries to compare the damge estimation method of floating netcage aquaculture fisheries with that of natural aquaculture fisheries using conventional theory of the population biology of living resources characterized with age distribution.

Three-dimensional trajectories of cultivated Pacific bluefin tuna Thunnus orientalis in an aquaculture net cage

AEI Aquaculture Environment Interactions Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AEI 4:81-90 (2013) - DOI: https://doi.org/10.3354/aei00075 Three-dimensional trajectories of cultivated Pacific bluefin tuna Thunnus orientalis in an aquaculture net cage Kazuyoshi Komeyama1,*, Minoru Kadota2,3,*, Shinsuke Torisawa2, Tsutomu Takagi2,** 1Faculty of Fishery, Kagoshima University, 4-50-20 Shimoarata, Kagoshima 890-0056, Japan 2Department of Fisheries, Faculty of Agriculture, Kinki University, 3327-204 Naka-machi, Nara 631-8505, Japan 3Temple University, 4-1-27 Mita, Minato-ku, Tokyo 109-0073, Japan *These authors contributed equally to this work**Corresponding author. Email: tutakagi@nara.kindai.ac.jp ABSTRACT: Swimming trajectories of aquatic animals that are estimated using the dead-reckoning technique below the sea surface tend to have very large associated observational errors. Therefore, the aim of the present study was to develop a technique for removing accumulated errors from such trajectories for Pacific bluefin tuna Thunnus orientalis. Horizontal and vertical speeds and heading angle were measured in an aquaculture net cage using 2 types of data loggers, and current velocity was recorded at a depth of 12 m to measure the tidal current speed around the net cage. Fourier analysis indicated that the primary source of error in trajectory estimates was the effect of ocean currents, which resulted in drift, and further analysis revealed that the frequency contributing to drift was consistent with the low-frequency signal in a spectrum analysis of horizontal speed. Therefore, a high-pass filter was applied to horizontal speed data to remove any frequencies lower than the cut-off frequency (0.0015 Hz), following which these data were back-transformed into a time domain that no longer included the drift effect caused by the current. The reconstructed trajectories fit within the inner diameters of the net cage, indicating that they were realistic. To confirm the validity of the resultant swimming trajectories, a flume tank experiment was conducted, which demonstrated that the high-pass filter effectively removed current drift from the estimated trajectory. Furthermore, since the method was estimated to have a precision of approximately 0.20 m, it not only allows the 3-dimensional trajectories of circling tuna to be estimated but can also be applied to the behavior of fish in the wild. KEY WORDS: Dead reckoning · Behaviour · Submerged net cage Full text in pdf format PreviousCite this article as: Komeyama K, Kadota M, Torisawa S, Takagi T (2013) Three-dimensional trajectories of cultivated Pacific bluefin tuna Thunnus orientalis in an aquaculture net cage. Aquacult Environ Interact 4:81-90. https://doi.org/10.3354/aei00075 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AEI Vol. 4, No. 1. Online publication date: June 26, 2013 Print ISSN: 1869-215X; Online ISSN: 1869-7534 Copyright © 2013 Inter-Research.

Re-oligotrophication as a challenge for tropical reservoir management with reference to Itaparica Reservoir, São Francisco, Brazil

The process of reservoir eutrophication has been recognised as a central problem in tropical reservoir environmental quality. Effects of eutrophication are complex interactions involving a decrease in water quality, especially loss of aquatic biodiversity, occurrence of undesired species such as cyanobacteria with its cyanotoxins, mass development of macrophytes such as Egeria densa with its mechanical impact on turbines, and an increase in greenhouse gas emissions, mainly of methane. The eutrophication process can be described by the OECD critical load concept or related models. The phosphorus use efficiency is given by the Chl a-P - relationship, indicating eutrophic conditions by only 10 μg L(-1) P in Itaparica Reservoir, Brazil. Eutrophication of the reservoir is quantified for internal phosphorus sources (inflow, mineralisation of inundated soils and vegetation, net cage aquaculture) and external ones (agriculture, emissions of natural caatinga vegetation and rural communities) The actual internal P load is calculated to be 0.40 g m(-2) a(-1), and the critical P load is given with 1.20 g m(-2) a(-1). The external P load amounts about 1.16 g m(-2) a(-1) and thus exceeds the critical export rate of 7.1 kg km(-2) a(-1) by 50%, thus a bundling of measurements has to be considered when attempting to promote re-oligotrophication.

Identification and expression analysis of a CC chemokine from cobia (Rachycentron canadum)

Chemokines are small, secreted cytokine peptides known principally for their ability to induce migration and activation of leukocyte populations and regulate the immune response mechanisms. The cobia (Rachycentron canadum), a marine finfish species, has a great potential for net cage aquaculture in the South China Sea. We isolated and characterized a CC chemokine cDNA from cobia-designated RcCC2. Its cDNA is 783bp in length and encodes a putative protein of 110 amino acids. Homology and phylogenetic analysis revealed that the RcCC2 gene, which contains four conserved cysteine residues, shares a high degree of similarity with other known CC chemokine sequences and is closest to the CCL19/21 clade. The mRNA of RcCC2 is expressed constitutively in all tested tissues, including gill, liver, muscle, spleen, kidney, head kidney, skin, brain, stomach, intestine and heart, but not blood, with the highest level of expression in gill and liver. The reverse transcription quantitative polymerase chain reaction was used to examine the expression of the RcCC2 gene in immune-related tissues, including head kidney, spleen and liver, following intraperitoneal injection of the viral mimic polyriboinosinic polyribocytidylic acid, formalin-killed Vibrio carchariae (bacterial vaccine) and phosphate-buffered saline as a control. RcCC2 gene expression was up-regulated differentially in head kidney, spleen and liver during 12h after challenge. These results indicate that the RcCC2 gene is inducible and is involved in immune responses, suggesting RcCC2 has an important role in the early stage of viral and bacterial infections.

Effects of net cages on the vertical distribution of zooplankton in a semi-arid reservoir, northeastern Brazil

AIM: Carneiro reservoir is an aquatic environment used for net cage aquaculture activities, located in the semi-arid region of northeastern Brazil. Vertical distribution was evaluated in order to determine the effects of organic enrichment induced by aquaculture on zooplankton movements. METHODS: three replicate samples were collected during midday and midnight at each of three depths along the water column (i.e. surface: 0 m; middle: 2 m and bottom: 4 m) at two sites (near and far from the net cages). Samples were collected using a 3 L volume capacity Van Dorn bottle. The collected individuals were preserved in a 4% formaldehyde solution saturated with sugar and, later, identified and counted on a Sedgwick-Rafter chamber under a microscope, considering a minimum of 100 individuals per subsample. RESULTS: higher species richness and density were observed at the N station (nearby the net cages) compared to the F station (distant from the net cages). With few exceptions, Rotifer species did not exhibit typical vertical migration patterns, concentrating at bottom depths during daytime and at intermediate depths during nighttime. Brachionus dolabratus and Hexarthra mira were the only species to show reverse vertical migration at the N station, in opposition to patterns of the cyclopoid copepod Termocyclops crassus. Furthermore, vertical migration patterns were not clear for Cladocera and Copepoda species nearby the net cages, but were rather clear at the F station. CONCLUSIONS: the presence of fish net cages increased zooplankton species richness (mostly rotifers) and density. Vertical movements were more pronounced at sites distant from net cages, suggesting that the increased food availability reduced the need for the typical vertical movements during daytime at sites nearby the net cages.

Modelling of current loads on aquaculture net cages

In this paper we propose and discuss a screen type of force model for the viscous hydrodynamic load on nets. The screen model assumes that the net is divided into a number of flat net panels, or screens. It may thus be applied to any kind of net geometry. In this paper we focus on circular net cages for fish farms. The net structure itself is modelled by an existing truss model. The net shape is solved for in a time-stepping procedure that involves solving a linear system of equations for the unknown tensions at each time step. We present comparisons to experiments with circular net cages in steady current, and discuss the sensitivity of the numerical results to a set of chosen parameters. Satisfactory agreement between experimental and numerical prediction of drag and lift as function of the solidity ratio of the net and the current velocity is documented.

Sustainable Fish Cage Aquaculture in Cirata Reservoir West Java, Indonesia: A System Dynamics Approach

The aims of this research were to identify and analyze processes causing fish productivity dynamic, to construct the model, and to design policy for sustainable Floating net cage aquaculture (FNCA) using system dynamics approach. The result of this research showed that the acceleration policy scenario gave a better performance in fish productivity and water quality than that in eutrophication policy scenario. On the other hand, the acceleration policy scenario created the higher fish stocking density, environmental cost and fish price than the eutrophication scenario. The simulation showed that fish productivity fluctuated by changing some importance parameters of the model such as FNCA unit regulation, aeration and change of fish stocking density.

Sustainable Fish Cage Aquaculture in Cirata Reservoir West Java, Indonesia: A System Dynamics Approach

The aims of this research were to identify and analyze processes causing fish productivity dynamic, to construct the model, and to design policy for sustainable Floating net cage aquaculture (FNCA) using system dynamics approach. The result of this research showed that the acceleration policy scenario gave a better performance in fish productivity and water quality than that in eutrophication policy scenario. On the other hand, the acceleration policy scenario created the higher fish stocking density, environmental cost and fish price than the eutrophication scenario. The simulation showed that fish productivity fluctuated by changing some importance parameters of the model such as FNCA unit regulation, aeration and change of fish stocking density.