Fishtraps are one of the more common monuments recorded along the intertidal zone. Fishtrap sites have been recorded in English, Welsh and Irish estuaries.
Figure 14: Fish-traps in the Inner Moray Firth demonstrate the different results from cartographic survey compared with coastal fieldwork. A combination of desk-based and fieldwork can produce results that form the empirical basis for further applied research, ©RCAHMS.
The fishtraps recorded during the inner Moray Firth coastal zone assessment survey (see http://www.scapetrust.org/html/fishtraps.html) were concentrated in two locations; the Beauly Firth and the Cromarty Firth, situated on shallow gradient mud or sand flats. They were built during the 17th-19th centuries to catch fish, especially the salmon that were abundant in the Inner Moray Firth. Seasonal runs of migratory salmon and sea trout swim through marine river channels that at low water often act as holding pools (Hale 2003). The fish would then use the ebb or flood tide to progress further down or upstream. The traps were placed at right-angles or obliquely to the channels so that the fish could be prevented from continuing their journey. Subsequently, as the tides fell the fish would be forced into the angles of the traps where water would pool and they would be unable to swim upstream or towards MHWM (Mean High Water Mark) and could then be caught with hand nets or in static nets.
Three different types of fish trap have been identified from documentary evidence: yairs, stake nets and bag nets. Yairs are curvilinear stone or wooden structures that run at right angles to the shoreline and curve, usually upstream, to form an arc. Wooden stakes interwoven with wattle have been recorded in some yairs, which show complex wattle and stake features at points along their length. Other yairs have been recorded with zigzag plans, designed to trap fish on both the ebb and the flood of the tide. Stake net traps comprise lines of stone mounds into which wooden stakes were driven and between which nets were strung. The third group of fish-traps are bag nets, comprising single lines of nets with stakes at either end, usually at MLWM (Mean Low Water Mark). Evidence of these traps were found as single mounds.
Sixty two fish-traps were recorded in the survey area, compared with over 70 sites marked on cartographic sources dating between 1817-1909. Although the variation is not necessarily significant because it does not define the time-depth of individual monuments, it does indicate that the survival of these monuments is dependent on environment and situation. The surviving sites are located in sheltered situations in the Beauly Firth, Munlochy Bay and the Cromarty Firth and there are no remains found on the rocky shorelines in between these firths and bay. All of the sites recorded were found to be in poor condition, probably caused by the effects of coastal erosion and/or accretion.
Figure 15: Tidal fish trap at Eilean na Carraidh, Mull. Both place name evidence and the archaeological remains enable the types of research into these relatively common features, to be multi-disciplinary and nationwide in their scope ©RCAHMS SC576116
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