Environmental Engineering Reference
In-Depth Information
few centimetres of sediment and is also highly mobile, making it well adapted to a constantly changing
sand habitat The burrowing crab or masked crab
Corystes cassivelaunus
is also a conspicuous species in
this habitat, being adapted to the same conditions; it can also be found along the beaches (Fig. 64).
The brittlestars
Ophiura ophiura
and
Amphiura brachiata
occur in large numbers in the bay together
with the large starfish
Asterias rubens
and
Astropecten irregularis
. Molluscs include the small opistho-
branch
Philine aperta
, the common whelk
Buccinium undatum
and the dog-whelk. Cuttlefish
Sepia offi-
cinalis
arealsopresent.Cuttlefishhaveaninteriorshellthatiscalledacuttlebone,andthesearefrequently
washed ashore onto the Gower beaches. They are chambered and filled with gas that acts as a buoyancy
control.
Despite the protected status of Carmarthen Bay, its seabed communities are currently under serious
threatfromthedevelopmentofanunsustainablefishery.Localandinternational fishing-industryinterests
are eager to deploy hydraulic fishing gear to harvest razor shells for sale overseas. The hydraulic blade
dredgeisgenerallyregardedbymarineecologistsasoneofthemostdestructivefishingmethods,because
of the harm it causes to soft-sediment areas. It operates by directing water jets into the seabed in order to
liquefy the sediment; suspending the shellfish in a slurry that is then sieved by the mesh of the dredge.
Hydraulicdredgesareanefficientmethodofharvestingshellfish,buthavebeenfoundtoseriouslydisturb
benthic invertebrates and redistribute the sediment habitat. Unfortunately the area is not alone in being
threatened by expanding shellfish fisheries; a similar situation exists in St Brides Bay, Pembrokeshire.
