Late Mesolithic Fish Traps from the Liffey Estuary, Dublin, Ireland
McQuade, Melanie, O'Donnell, Lorna, Antiquity
An opportunity to investigate in advance of new construction led to the discovery of five Mesolithic hazel fish traps some 6.3m below mean sea level in the River Liffey. Closely paralleled on the continent of Europe they imply a well organised community that knew how to catch fish using the tide, to make wattle-work and baskets and who undertook coppicing on an eight year cycle in about 6100-5700 cal BC. The likelihood of more Mesolithic remains under European towns that have remained attractive to fishers and settlers has considerable implications for Cultural Resource Management. Do we always know how to find and access such delicate and important traces?
Keywords: Mesolithic, Ireland, coppicing, CRM, fish, fish traps, woodland
In 2004 the remains of Late Mesolithic fish traps were discovered during development works in Dublin's Docklands (Figure 1). Not only are these the earliest securely-dated fish traps in Ireland or the UK but they are also amongst some of the earliest examples recorded in Europe. Moreover, the remains were remarkably well preserved and their excavation yielded rare and important evidence for woodworking techniques and possible woodland management during the Late Mesolithic period.
The fish traps were discovered during archaeological monitoring of deep excavation for basement foundations on a site at North Wall Quay, Dublin (National Grid Coordinates 317350/2344459) (Figure 2). Monitoring was undertaken as a requirement of the planning permission, following recommendations made in an Environmental Impact Study. The construction of the basement required excavation several metres below present sea level. This was facilitated by the insertion of secant piles and the constant operation of industrial pumps. After the discovery of the fish trap remains, an area measuring 60m east-west by 16m was excavated by a team of archaeologists led by Melanie McQuade. A previously unrecorded Mesolithic shoreline and the remains of up to five wooden fish traps and related features were uncovered at a level of minus 5m Ordnance Datum (1) (Figure 3). The shoreline was approximately 30m north of the present quay wall. It was either the shore of an island within the Liffey estuary, which may only have been exposed at low tide, or was a former bank of the river channel.
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The traps were set in the estuarine silts and were located between 1.20m and 13m south of the gravel shoreline (Figure 3). The force of successive tides had resulted in the fragmentation of the traps and the remains were preserved under a build-up of silt. Since none of the traps survived intact it has not been possible to determine with certainty which, if any, of the remains formed part of the same structure. However, it was possible to date them and they all returned Late Mesolithic dates of between 7144 [+ or -] 46 BP and 6932 [+ or -] 48 BP or 6100-5720 cal BC (WK 16556-WK 16560, OxCal 3.10). The dates fall within two clusters (Table 1), but since these overlap they do not represent distinct phases of activity. What is clear, however, is that the site was a valuable fishing ground for a considerable period of time (spanning 200 years) during the Late Mesolithic.
The fishing ground
The five fish traps and the stakes and wattle pieces scattered across the site were the remains of structures that operated on the principle of passive fishing. Fish swimming in with the incoming tide were caught in the traps and were retrieved by the fishermen at low tide, when the structures were accessible from the shore. All the remains were so closely dated that they could have been used by the same or successive generations of fishermen. The system can be resolved into weirs of wattle work, designed to guide the fish, and traps, designed to catch and retain them.
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Wattle weir (6090-5890 cal BC)
Fragments of two wattle fences and a small panel which lay horizontally between them were probably the remains of an ebb weir (Figure 3). …