Trust Regional Historic Environment Record
Weir Beneath Gorad Ddu, Llanfair Pwllgwyngyll
Primary Reference Number (PRN) : 14617 Trust : Gwynedd Community : Llanfair Pwllgwyngyll Unitary authority : Ynys Mon NGR : SH54647159 Site Type (preferred type first) : Medieval FISH WEIR Status : Scheduled Monument
Description : A 4m wide linear bank of small stones runs through the centre of the area enclosed by Gorad Ddu. This appears to be the remains of an earlier trap. Further ill-defined walls can be seen on the outside of Gorad Ddu which may be associated with this site. (Hopewell, 2000).
There are the remains of a wall running north south, at right angles to the shore within Gorad Ddu. This badly collapsed structure, which, in places, is represented by a spread of small stones, can be traced for 65m and terminates in the accumulation of fine silt just north of the main weir wall. It may represent the remains of an earlier fish weir constructed in the same design as Gorad y Gyt on the southern side of the Menai Straits (GAT I 997).
On the seaward side of the main wall of Gorad Ddu, close to the rocky outcrop, is another construction of large boulders as shown in Fig 2. Even at very low tides this is difficult to identify but it appears to consist of a wide wall extending 80m in a south-easterly direction from the base of the main weir. It then turns at an acute angle to the south-west and continues for a further 20m. This section shows more clearly along the inner face of the wall. The masonry at this apex appears to be I Om wide but at no time during the survey was it entirely clear of the sea to allow a close or full inspection. This structure may represent part of an earlier fish trap although it does not align with the remains of the earlier wall to the north. It is unlikely that this is the hook-end of a fish trap as it is facing the wrong way to catch fish on an ebb tide. Some fish traps were designed to operate on the flood tide but they need a nonreturn opening at the apex that is not apparent in this case (Davis 1958, 30). If this structure is part of an earlier fish weir it would indicate a considerable rise in sea level in the area as it would not be possible to harvest the catch on any but the very lowest tides today. Momber suggested such a rise during a study of Gorad Beuno near Caernarfon a few miles west of Gorad Ddu. He found a net sea level rise in Caernarfon Bay of about 3m in the last millennium (Momber 1991, 108). (Richards, 1998),