Impact of near shore nourishment on benthos and fish in the near shore environment.
Type:
Presented during:
CEDA Dredging Days 2005 - Dredging: The Extremes, Rotterdam
Authors:
Ingvardsen S.M., Laustrup C., Støttrup J.G. and Dolmer P.
Abstract: Several reports and investigations have in the past few years indicated a connection between nourishment and the amount of benthos and fi sh both in the near-shore environment and in adjacent deeper water. The Danish Coastal Authority has used nourishment as a part of coastal defence on the west coast of Jutland since 1973. One of the reasons is that nourishment is a more natural form of coastal defence than groynes and breakwaters. To fi nd out whether there are negative effects on the local benthos and fi sh populations a biological monitoring plan based on a BACI design was developed by the Danish Institute for Fisheries Research.
This investigation, which began in 2002, focused on nourishment placed at the near-shore between groynes on the west coast of Jutland. The investigation concerns one nourishment area and two reference areas. The differences in the nourishment area and two reference areas are discussed taking into account differences in site characteristics and the time of year.
This study showed a connection between nourishment and a short-term negative effect on the populations of some benthos. There were also examples showing that juvenile fi sh are attracted to places that recently have been nou-rished. It is discussed if using nourishment sand with a slightly larger grain size than the natural sands can cause a short-term negative effect on the local populations of benthos and juvenile fi sh in the near-shore environment.
Note that this investigation only concerns deposit of sand, not the extractions in the North Sea. The response of the populations of benthos in the extraction areas has been studied in previous investigations.
Keywords: Nourishment, Benthos, Fish, Near-Shore Environment.