Hauton, C., Hall-Spencer, J.M. and Moore, P.G.
An experimental study of the ecological impacts of hydraulic bivalve dredging on maerl.
ICES Journal of Marine Science, 60, (2), . (doi:10.1016/S1054–3139(03)00015-8).
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A short-term experiment to assess the ecological impact of a hydraulic blade dredge on a
maerl community was carried out during November 2001 in the Clyde Sea area on the west
coast of Scotland. A fluorescent sediment tracer was used to label dead maerl, which was then
spread out on the surface of sediment to act as a proxy for living maerl. The fauna collected by
the dredge was dominated by the bivalves Dosinia exoleta and Tapes rhomboides, which
were found to be intact. The target razor clams Ensis spp. were caught in low numbers, which
reflected the low abundance of this genus within the maerl habitat. The hydraulic dredge
removed, dispersed and buried the fluorescent maerl at a rate of 5.2 kgm2 and suspended a
large cloud of sediment into the water column, which settled out and blanketed the seabed to a
distance of at least 8m either side of the dredge track. The likely ecological consequences of
hydraulic dredging on maerl grounds are discussed, and a case is made for protecting all
maerl grounds from hydraulic dredging and establishing them as reservoirs to allow for the
recruitment of commercial bivalve populations at adjacent fished sites.
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