Ancient Monuments

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Trecastell Fish Weir

A Scheduled Monument in Llangoed, Isle of Anglesey (Ynys Môn)

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Latitude: 53.2861 / 53°17'10"N

Longitude: -4.0699 / 4°4'11"W

OS Eastings: 262107

OS Northings: 378573

OS Grid: SH621785

Mapcode National: GBR 0Z0F.NQ

Mapcode Global: WH53W.GN5M

Entry Name: Trecastell Fish Weir

Scheduled Date: 19 November 2002

Source: Cadw

Source ID: 1032

Cadw Legacy ID: AN141

Schedule Class: Maritime

Category: Fish weir

Period: Post Medieval/Modern

County: Isle of Anglesey (Ynys Môn)

Community: Llangoed

Traditional County: Anglesey


The monument consists of the well-preserved remains of a 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. Trecastell Fish Weir is rectilinear, defined by spread banks of stone. The inner wall runs at 90 degrees to the shore and is some 310m long. It varies in structure from a 20m wide bank to a double line of facing-stones from 1.1 to 1.6m wide. The outer wall turns at a right angle and runs parallel to the shore for some 250m.

The monument is of national importance for its potential to enhance our knowledge of post-medieval maritime agricultural practices. It is associated with the unusual weir at Gorad Friars Bach (SH 6150 7770) and the pair of weirs at Aberlleiniog (SH 6250 7920) and therefore has significant group value. 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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