An experimental study on the impact of clam dredging of soft sediment macroinvertebrates (ENRR013)

The impact of clam dredging on intertidal invertebrate fauna has been assessed by undertaking an experimental study using a modified oyster dredge. A study area was established in Langstone Harbour at a site known as Chalkdock Lake. The fauna were seen to be either completely removed or considerably reduced by the action of the dredge. This was statistically demonstrated using community structure measures and individual abundance values. The annelids were seen to be most badly affected by the action of the dredge with the exception of Tubificoides benedeni and a Phyllodocid. The abundance of the bivalve species was greatly reduced, but some individuals were found in the post-dredge samples. These were all small specimens and were thought to have been disturbed by the dredge and re-deposited afterwards. No clear recovery of the fauna was evident over the period of the study. The principal species colonising after dredging are predicted to be the small opportunistic annelids and the small re-deposited bivalves. It was concluded that the re-colonisation of the dredged areas would be poor, in terms of the value to avifauna, if intensive dredging was to be undertaken.

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