This fish trap is a Scheduled Ancient Monument. It consists of two arms adjoined to either side of a rock outcrop. The western arm comprises a dry stone wall extending from the shore in a southerly direction for some 65m before terminating with a 'U' shaped sluice. This arm stands up to 3m height, with an additional 45cm buried in silt. The outer faces of the walls comprise square blocks with a core filled with smaller stones. The sluice is constructed from good quality masonry, and has a groove in each side to hold a wattle sluice gate. A second wall curves away from the sluice in an easterly direction for some 70m, terminating near the northern tip of the outcrop. Adjacent to the end of the wall is the base of a building. A 65m length, 6m width artificial channel has been dug through the centre of the outcrop. This would have funnelled fish on the ebb tide. The second arm extends in an easterly direction from the eastern tip of the outcrop, and is only visible for some 30m. A further wall of small stones, some 4m wide, is situated between the rock outcrop and the western arm. It extends from the shore approximately 20m from the island, running south for some 70m. It is thought that this is the remains of an ealier fish trap. Approximately 30m west of the western arm is a fish holding pool and possible dock.

Sources include:
Gwynedd Archaeological Trust, 2012, Historic Environment record
National Assembly of Wales, 2009, vertical AP
Turner, R. Fish Weirs and Fish Traps, in: Davidson, A. 2002. The Coastal Archaeology of Wales, CBA Research Report 131, pg 96-99.

Maritime Officer, RCAHMW, January 2011.