Three-dimensional deformation of a large circular flexible sea cage in high currents: Field experiment and modeling

Klebert, Pascal; Patursson, Øystein; Endresen, Per Christian; Rundtop, Per; Birkevold, Jens; Rasmussen, Heini Winthereig

doi:10.1016/j.oceaneng.2015.04.045

Cited by 91 publications

(62 citation statements)

References 29 publications

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“…Several factors influence this reduction in speed, such as net dimensions, biofouling, presence of fish and potentially the deformation of the sea cages (Klebert et al 2013, Gansel et al 2014, Winthereig-Rasmussen et al 2016). Klebert et al (2015) report a reduction of 21.5% in current speed from a reference point outside to inside a fish pen, which compares well with the reduction of 20% found applying the empirical method of Løland (1991). Higher reductions have however been reported when the sensors are located such that fish may influence the measurements (Johansson et al 2014).…”

Section: Current Class Definitions Based On Fish Behavioursupporting

confidence: 65%

“…The stronger water currents may be advantageous, as higher water ex -change rates result in larger nutrient assimilation capacity, higher levels of dissolved oxygen and generally better water quality (Johansson et al 2007, Holmer 2010, Klebert et al 2013, Gentry et al 2017). However, stronger water currents may induce excessive loads on the farm structure and large net deformations, resulting in challenging conditions for farming operations (Lader et al 2008, Kristiansen & Faltinsen 2012, Bjelland et al 2015, Klebert et al 2015, Gansel et al 2018. The currents may also be evaluated from a fish-welfare perspective, the primary concern being how the magnitude, duration *Corresponding author: kristbjorg.jonsdottir@ntnu.no Fish welfare based classification method of ocean current speeds at aquaculture sites and frequency of strong current events affect behaviour, growth, stress and risks of mortality (Johansson et al 2014, Solstorm et al 2015, Remen et al 2016, Hvas & Oppedal 2017.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Fish welfare based classification method of ocean current speeds at aquaculture sites

Jónsdóttir¹,

Hvas²,

Alfredsen³

et al. 2019

Aquacult. Environ. Interact.

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A major trend in marine aquaculture is to move production to more exposed sites with occasionally rough ocean current events. However, it is unclear whether fish will thrive in these extreme environments, since thorough descriptions of ambient current conditions with regards to fish welfare is lacking. In the present study, ocean current data were collected using acoustic Doppler current profilers at 5 exposed sites along the Norwegian coast over minimum periods of 5 mo. To evaluate welfare risks, current data was compared to known limits of swimming capabilities, such as onset of behavioural changes and critical swimming speeds (U crit ), of Atlantic salmon Salmo salar and lumpfish Cyclopterus lumpus. Specifically, at each site, current speeds were classified into 6 categories based on expected impact on swimming behaviours of Atlantic salmon, and duration of currents within each category were inspected using a homogeneous and non-homogeneous criterion for the water column. Current speeds were then compared with projected U crit at relevant temperatures and fish sizes of Atlantic salmon and lumpfish. Furthermore, a detailed characterization of extreme events at the most exposed site was performed. Of the 5 locations, only 1 exceeded the U crit of Atlantic salmon, while all sites featured currents above U crit of lumpfish for up to 33 h at a time. These results suggest that responsible Atlantic salmon farming is possible at sites considered exposed, while lumpfish should be restricted to more sheltered environments. The presented method can be applied for other aquaculture fish species if adequate data are available.

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Section: Current Class Definitions Based On Fish Behavioursupporting

confidence: 65%

Section: Introductionmentioning

confidence: 99%

Fish welfare based classification method of ocean current speeds at aquaculture sites

Jónsdóttir¹,

Hvas²,

Alfredsen³

et al. 2019

Aquacult. Environ. Interact.

View full text Add to dashboard Cite

show abstract

“…For example, the indication of overestimation at stations 7 and 9 at location 2 ( Figure 10B) is consistent with the model slightly underestimating current speeds there (Figure 6). Depending on the bathymetry, reduced surface currents might increase bottom currents, however (Klebert et al, 2015), and the interplay between a number of processes and input data is what eventually determines the amounts of bottom deposits.…”

Section: Simulated and Observed Mud Thicknessmentioning

confidence: 99%

Spatiotemporal Dispersal and Deposition of Fish Farm Wastes: A Model Study from Central Norway

et al. 2017

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A spatially explicit coupled hydrodynamic-mass transport model system was used to simulate dispersal of particulate organic matter from Atlantic salmon (Salmo salar) farming in central Norway. Model setups of 32 m horizontal resolution were run for periods of up to 650 days for 3 sites of different oceanographic characteristics: one fjord location, one medium-exposed location influenced by fjord water, and one coastal location. Records on feed used for each cage at each location were converted to feces released based on a published mass balance model. The results from the simulations were compared with scores from corresponding mandatory benthic surveys (MOM-B) of the sediment layer beneath the farms. The correspondence between simulated and measured thickness of the sediment layer was good, and improved with the inclusion of resuspension processes. At all sites the distribution of organic matter in the bottom layer was non-homogeneous, with significant temporal variation and transport and settling of matter up to at least 0.5 km away from one of the farms. Our results indicate that the monitoring practice used in Norway until now, with a few sediment grab samples taken mainly within the fish farm, may not adequately determine the areal impacts of all salmon farming operations. The patchy distribution of organic matter and the correspondence between simulation and survey results is attributed to the use of full 3D current fields of a high spatiotemporal resolution and a good model for resuspension processes that some previous model studies have failed to properly account for.

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“…To maintain growth and meet demand, technological advancements which improve efficiency and sustainability are required (Diana et al 2013). Most cages used in salmon aquaculture are 'gravity' type cages: weighted nets suspended in the water column beneath a surface collar (Klebert et al 2015). Average cage size has grown steadily since the inception of the salmon industry in the 1970s.…”

Section: Introductionmentioning

confidence: 99%

Cage size affects dissolved oxygen distribution in salmon aquaculture

Oldham¹,

Oppedal²,

Dempster³

2018

Aquacult. Environ. Interact.

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Atlantic salmon aquaculture is shifting toward larger cages, but the water quality implications of this shift are unknown. While larger cages could improve profitability through economies of scale, they may increase the risk of low dissolved O 2 (DO) conditions due to reduced water exchange. Low DO conditions reduce feed intake, meaning that the benefits of shifting to larger cages must be weighed against potential negative impacts on fish growth. To test the impact of cage size on DO distribution, we recorded DO saturation in several circular cages of 2 different sizes on a commercial salmon farm: 6 with 168 m and 4 with 240 m circumference. Static strings of DO loggers at 1, 4.5, 8, 12 and 16 m depths recorded DO saturation once every 60 s throughout a 10 d period in midsummer. Overall, DO levels in standard 168 m circumference cages were suitable for salmon feeding and growth. DO levels were highly variable (57 to 134% saturation), and were lower in cages than at the reference site. On average, DO saturation decreased with depth, and was lowest during the early morning hours. Lowest DO measurements occurred in the large 240 m circumference cages, where 1 in 20 of all recordings were at levels known to reduce salmon feeding and growth. DO levels in larger cages can suit salmon production, but site-specific environmental conditions throughout the year must be considered to ensure there is sufficient capacity to tolerate reduced water exchange.

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Three-dimensional deformation of a large circular flexible sea cage in high currents: Field experiment and modeling

Cited by 91 publications

References 29 publications

Fish welfare based classification method of ocean current speeds at aquaculture sites

Fish welfare based classification method of ocean current speeds at aquaculture sites

Spatiotemporal Dispersal and Deposition of Fish Farm Wastes: A Model Study from Central Norway

Cage size affects dissolved oxygen distribution in salmon aquaculture

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