Neumeier U., Friend P.L., Gangelhof U., Lunding
J., Lundkvist M., Bergamasco A., Amos C.L. & Flindt M. (in press) The influence of fish feed pellets
on the stability of seabed sediment, a laboratory flume investigation. Estuarine, Coastal and Shelf
Science.
Abstract
Superfluous fish food settling below fish farms can have an negative impact on the seabed. To
aid in the assessment of this impact a series of flume experiments, designed to mimic seabed
conditions below a fish farm, was conducted with the aim of examining the effects of fish
pellets on the stability of fine sediments. Artificial beds, with varying quantities of fish pellets
incorporated both within the sediment matrix and lying on the sediment surface, were allowed
to consolidate for different periods of time ranging from 1 to 10 days, and then subjected to
erosion experiments. In flume experiments containing fish pellets, a bacterial biofilm
developed at the sediment-water interface after a few days. In the control experiments (no fish
pellets), a diatom biofilm caused extensive stabilisation of the surface sediment. The erosion
experiments showed that the addition of fish pellets reduced the surface erosion threshold by
more than 50%. The stability decrease was more pronounced in the experiments with greater
amounts of pellets. Evidence of drag reduction due to high suspended sediment concentration
was also observed. This phenomenon is discussed and a correction formula is proposed for
the effective shear stress experienced by the bed.
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