This fish trap is a Scheduled Ancient Monument and has been dendrochronolically dated to 1556. Erosion by the Ogwen channel has uncovered earlier phases comprising posts with some remnants of wattle. It is located approximately 800m east of NPRN 518206, and is very similar in structure. This fish trap is described as 'Ogwen Weir' on modern and historical OS mapping, and is constructed from a narrow stone bank defined by slate and oak posts. The main fish trap is 'V' shaped, but its first arm is some four times longer than its second arm, measuring approximately 840m. Both arms point shoreward, with the apex pointing seaward (north). The remains of a sluice are evident at the apex. The second arm comprises the hook of the trap, measuring approximately 240m and runs in a southeasterly direction, terminating with a small arm (measuring some 25m) extending from it at right angles.1st- 4th edition OS mapping (1885-1947) depicts a third arm, comprising a second hook, which begins approximately 100m along the southeast (hook) arm of the main trap. The second hook runs parallel to the first, running approximately 100m in a northeasterly direction, before turning and running southeast for a further 320m. An historic Admiralty chart may depict earlier phasing of the fish trap. The chart depicts the trap in a slightly different position, also with two hooks which each run south for some 330m, parallel to the second and third arms. Historic mapping (1885-1947) also depicts a footpath, whose purpose appears to have been to service the fish trap. The footpath extends from Porth Penrhyn (from what is depicted as a muscle farm on modern OS mapping), and crosses through the south arm of NPRN 518206 (Cegin Weir Fish Trap) at which point a gap or gate is shown. The footpath then extends through the first arm, at which point a gap or gate is again depicted. The footpath then runs parallel to the first arm and terminates at the apex. Approximately 200m from the apex the footpath branches into two, with the second path heading northeast to link up tp the point where the second hook converges with the first.

Sources include:
Chart 1174-A4 date 1839
Gwynedd Archaeological Trust, 2012, Historic environment Record
Ordnance Survey, 2012, Mastermap
Ordnace Survey, 1885-8, 1st edition 25" Landmark
Ordnace Survey, 1898-1900, 2nd edition 25" Landmark
Ordnace Survey, 1912-20, 3rd edition 25" Landmark
Ordnace Survey, 1939-47, 4th edition 25" Landmark


Maritime Officer, RCAHMW, January 2011.