It is not much to look at, but the alignment speaks to a practice that was once central to life along this stretch of water: the trapping of fish using fixed structures built directly into the tidal landscape.

A fish weir of this kind typically consisted of a series of stakes or posts driven into the riverbed or mudflat, sometimes connected by wicker or netting, arranged to funnel fish into a trap as the tide receded. The structure recorded here runs roughly northwest to southeast for approximately 26 metres, sitting on level estuarine clays to the south-southeast of Graigue Island. It was documented in July 1994 by Aidan O'Sullivan, who described it as a post alignment and dated it tentatively to the post-medieval period. That broad designation, covering roughly the sixteenth century onwards, reflects the difficulty of pinning down such features without excavation or material analysis. Timber weirs leave little above the surface, and their age is rarely obvious from inspection alone.