Effects of waves and currents on gravity-type cages in the open sea

Huang, Chai Cheng; Tang, Hung-Jie; Liu, Jin‐Yuan

doi:10.1016/j.aquaeng.2008.01.003

Cited by 60 publications

(27 citation statements)

References 12 publications

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“…The authors suggest this relates to complex near-field hydrodynamics in the proximity of fish cages. As detailed in the Canadian case study, a range of factors may affect flow patterns, resulting in variable and fluctuating current directions (Petrell et al 1993, Huang et al 2008, Reid et al 2010, consequently leading to complex nutrient plume dynamics in the near-field or close to structures . In addition to hydrodynamic influences from cages (Løland 1993, Helsley & Kim 2005, Lader et al 2007, Le Bris et al 2007), near-cage currents can be affected by the swimming behavior of fish (Gansel et al 2011(Gansel et al , 2014 as postulated in the Norwegian case study.…”

Section: Physical Processesmentioning

confidence: 99%

Discrete water quality sampling at open-water aquaculture sites: limitations and strategies

Jansen¹,

Reid²,

Bannister³

et al. 2016

Aquacult. Environ. Interact.

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While environmental performance of cage-based aquaculture is most often monitored through benthic conditions, there may also be requirements that necessitate discrete, pelagic sampling. In the pelagic realm, adequately capturing the spatial and temporal dynamics of interest and attributing causality to aquaculture processes can be extremely challenging. Conditions are seldom ideal, and data adequacy concerns of discrete samples collected at open-water aquaculture sites are not uncommon. Further exploration of these challenges is needed. Herein, we aim to explore considerations for study design, analysis, and data interpretation of discrete pelagic sampling. As examples, we present 2 case studies where limited sampling occurred under conditions of complex pelagic dynamics. A Norwegian case study quantified particle abundance around salmon farms, and aimed to highlight the effects of spatial−temporal variation on sampling design, the need for inclusion of companion parameters, and the benefits of a priori and a posteriori data interpretation strategies. A Canadian case study collected discrete samples to measure ammonium concentrations with continuous current measurements at an Integrated Multi-Trophic Aquaculture (IMTA) farm, to explore issues of complex hydrodynamics, reference site suitability, sampling resolution, data pooling, and post hoc power tests. We further discuss lessons learned and the implications of study design, ambient conditions, physical processes, farm management, statistical analysis, companion parameters, and the potential for confounding effects. Pragmatic consideration of these aspects will ultimately serve to better frame the costs and benefits of discrete pelagic sampling at open-water aquaculture sites.

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Section: Physical Processesmentioning

confidence: 99%

Discrete water quality sampling at open-water aquaculture sites: limitations and strategies

Jansen¹,

Reid²,

Bannister³

et al. 2016

Aquacult. Environ. Interact.

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show abstract

“…Such a significant reduction of the water speed was found to be important for the exchange properties of oxygen and waste transport inside cages (Fredriksson et al 2007). On the other hand, the flowing water exerts a force on the cage system, which can be an important factor for cage design (Fredriksson et al 2003, Rasmussen & McLean 2004, Fredriksson et al 2007, Huang et al 2008, Lee et al 2008, DeCew et al 2010, Dong et al 2010. Previous studies have generally ignored the effect of the aquaculture system when investigating hydrodynamic processes and sediment transport in culture farms using circulation models, except for a few, e.g.…”

Section: Introductionmentioning

confidence: 99%

A three-dimensional hydrodynamic model for aquaculture: a case study in the Bay of Fundy

Wu¹,

Chaffey²,

Law³

et al. 2014

Aquacult. Environ. Interact.

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Impacts of aquaculture on the local current field and the erosion of the bottom sediment in the Bay of Fundy, Canada, have been investigated with a 3-dimensional hydrodynamic model. The model is evaluated against independent observations of the current. Model results show that the presence of fish cages restricts water flow and reduces the velocity in the surface layer occupied by the cages, but enhances the water velocity in the bottom layer beneath the cages. Sensitivity studies show that the change in the flow velocity beneath the cages is sensitive to variations in the drag coefficient and the height of the fish cages. As the drag coefficient increases, the bottom velocity also increases until a steady state value is reached. For the cage height, however, the tidal speed beneath the cages first increases with cage height and then significantly decreases with further increasing height. The maximum increase in velocity occurs when the cage height is about half the local water depth (H/H 0 = 0.5, where H is the cage height and H 0 is the water depth). The increase in bottom velocity significantly speeds up the erosion of the bottom sediment. The model results also indicate that there is an optimal drag coefficient and an optimal cage height for a specific farm site. By utilizing the optimal drag coefficient and height, it is possible to speed up sediment erosion beneath the cages and, thus, decrease the environmental problems caused by accumulated fish farm waste.

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“…Lee, et al [6] suggested a mathematical model to analyze fishing cage system in current and wave including comparisons with experimental results. Huang, et al [7] investigated the effects of waves and currents on gravity-type cages and mainly focused on mooring tensions and volume reduction coefficients of the cage. In addition, Huang and Pan [8] conducted a fatigue analysis of a SPM-cage system under wave and current loads.…”

Section: Introductionmentioning

confidence: 99%

Response Prediction and Monitoring Feasibility of a Stow Net System Using Measured Environmental Data in the Southwest Coast of Korea

2018

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This paper investigates the response characteristics of a stow net under wave and current excitations, as well as the feasibility of its monitoring system to check net functionality and prevent loss of fishing gears. The stow-net model is based on one of existing types used in southwest coast of South Korea. The measured wave and current data there are acquired and inputted as environmental loads for numerical simulations. The Morison equation for a moving object with equivalent net model is utilized as the external-force estimator, which has been validated by many researchers regarding fish-cage studies. Since the modelling of all the net elements is inefficient in terms of computational time in time-domain simulations, cruder equivalent-drag net elements are devised with equivalent wet mass, projected area, and axial stiffness. The performance of stow net is highly influenced by current velocity. Stow nets submerge more in stronger currents, which results in less wave forces. The proposed monitoring system can provide useful information, such as net functionality and loss of stow net, using the minimum number of monitoring sensors.

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Effects of waves and currents on gravity-type cages in the open sea

Cited by 60 publications

References 12 publications

Discrete water quality sampling at open-water aquaculture sites: limitations and strategies

Discrete water quality sampling at open-water aquaculture sites: limitations and strategies

A three-dimensional hydrodynamic model for aquaculture: a case study in the Bay of Fundy

Response Prediction and Monitoring Feasibility of a Stow Net System Using Measured Environmental Data in the Southwest Coast of Korea

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