Ancient Monuments

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Gorad Ddu Fish Weir

A Scheduled Monument in Menai Bridge (Porthaethwy), Isle of Anglesey (Ynys Môn)

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Latitude: 53.2214 / 53°13'16"N

Longitude: -4.1796 / 4°10'46"W

OS Eastings: 254578

OS Northings: 371587

OS Grid: SH545715

Mapcode National: GBR 5M.155S

Mapcode Global: WH546.R9X8

Entry Name: Gorad Ddu Fish Weir

Scheduled Date: 31 October 2002

Source: Cadw

Source ID: 3907

Cadw Legacy ID: AN139

Schedule Class: Maritime

Category: Fish weir

Period: Post Medieval/Modern

County: Isle of Anglesey (Ynys Môn)

Community: Menai Bridge (Porthaethwy)

Built-Up Area: Menai Bridge

Traditional County: Anglesey


The monument consists of the remains of a very impressive and well-preserved fish weir, dating to the post-medieval period. A fish weir is usually characterised by a foundation of stone topped with a fence or row of stakes, often with nets attached forming an enclosure within a river or harbour and used for catching, or holding, fish. Gorad Ddu Fish Weir is defined by well-built, dry-stone walls and incorporates modified natural features. The weir walls stand to a maximum height of approximately 3m and are 1.2 to 1.5m in width. The inner wall runs southwards at a right angle from the shore for 70m before turning through 90 degrees to the east and running for 96m towards a low rocky island. The wall then continues for another 80m to the east of the island. A well-defined sluice can be seen in the western angle of the weir wall. The weir is first recorded in Baron Hill Estate papers dating to 1602.

The monument is of national importance for its potential to enhance our knowledge of medieval or post-medieval maritime agricultural practices. It retains significant archaeological potential, with a strong probability of the presence of associated archaeological features and deposits. The structure itself may be expected to contain archaeological information concerning chronology and building techniques.

The scheduled area comprises the remains described and areas around them within which related evidence may be expected to survive.

Source: Cadw

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