Duchy ownership within an estuary extends from a line across the mouth of the estuary to the highest point upstream to which the tide flows. Along each bank of an estuary and along the coastal foreshore, Duchy ownership is up to Mean High Water mark and along the coast this stops at the line of Lowest Astronomical Tide, beyond which is Crown seabed.
Statutory protection is provided in a number of areas by designations such as Site of Special Scientific Interest (SSSI) and Special Area of Conservation (SAC). Areas of Outstanding Natural Beauty (AONB) status provides extra planning controls over adjacent areas. Some man-made artefacts are protected by being scheduled by English Heritage as ancient monuments, such as the World War II boat scrubbing grids in the Dart estuary.
Other conservation effort is voluntary: The Helford River Voluntary Marine Conservation area is a good example and there are conservation officers for the Dart and Salcombe & Kingsbridge estuaries. The Duchy helps to support these initiatives financially.
Shellfish farming is the main commercial activity in the Duchy’s estuaries. The most important is the historic Duchy of Cornwall Oyster Farm on the Helford River. Mussels, clams and cockles are also farmed or taken from the wild and some commercial crab trapping serves the fishing bait industry.
There is a general right to temporarily drop anchor, but to have a regular mooring requires the consent of the owner of the sea or estuary bed. Most moorings are administered on the Duchy’s behalf by local authorities, statutory harbour authorities or private concerns such as sailing clubs and marina operators.