Bergen Open Research Archive

Numerical modelling of organic waste dispersion from fjord located fish farms

Bergen Open Research Archive

Show simple item record Ali, Alfatih Mohammed A. Thiem, Øyvind Berntsen, Jarle 2011-11-21T13:58:15Z 2011-11-21T13:58:15Z 2011-04-21
dc.identifier.citation Ocean Dynamics 61(7): 977-989 en
dc.identifier.issn 1616-7341
dc.description.abstract In this study, a three-dimensional particle tracking model coupled to a terrain following ocean model is used to investigate the dispersion and the deposition of fish farm particulate matter (uneaten food and fish faeces) on the seabed due to tidal currents. The particle tracking model uses the computed local flow field for advection of the particles and random movement to simulate the turbulent diffusion. Each particle is given a settling velocity which may be drawn from a probability distribution according to settling velocity measurements of faecal and feed pellets. The results show that the maximum concentration of organic waste for fast sinking particles is found under the fish cage and continue monotonically decreasing away from the cage area. The maximum can split into two maximum peaks located at both sides of the centre of the fish cage area in the current direction. This process depends on the sinking time (time needed for a particle to settle at the bottom), the tidal velocity and the fish cage size. If the sinking time is close to a multiple of the tidal period, the maximum concentration point will be under the fish cage irrespective of the tide strength. This is due to the nature of the tidal current first propagating the particles away and then bringing them back when the tide reverses. Increasing the cage size increases the likelihood for a maximum waste accumulation beneath the fish farm, and larger farms usually means larger biomasses which can make the local pollution even more severe. The model is validated by using an analytical model which uses an exact harmonic representation of the tidal current, and the results show an excellent agreement. This study shows that the coupled ocean and particle model can be used in more realistic applications to help estimating the local environmental impact due to fish farms. en
dc.language.iso eng en
dc.publisher Springer en
dc.rights ©The Author(s) 2011 en
dc.rights.uri en
dc.subject Fish farms en
dc.subject Waste dispersion en
dc.title Numerical modelling of organic waste dispersion from fjord located fish farms en
dc.type Peer reviewed eng
dc.type Journal article eng
dc.subject.nsi VDP::Agriculture and fishery disciplines: 900::Fisheries science: 920 en
dc.type.version publishedVersion eng
bora.peerreviewed Peer reviewed eng

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