A fish weir or fish trap is structure built of stone, reeds or wooden posts placed within the channel of a stream or at the edge of a tidal lagoon intended to capture fish as they swim along with the current. Fish traps on rivers or streams are circular, wedge-shaped or ovoid rings of posts or reeds, with an upstream opening. The posts are often connected by basketry netting or wattle fences: the fish swim in and are trapped within the circle or upstream of the current.
Tidal fish traps are solid low walls of boulders or blocks built across gullies: the fish swim across the top of the wall at spring high tides, and as the water recedes with the tide, they're trapped behind it. Fish weirs are sometimes thought of as fish farming (sometimes "aquaculture"), since the fish can live in the trap for a period until they are harvested. Often, according to ethnographic research, the fish weir is dismantled on a seasonal basis, allowing the fish to freely spawn.
Proof of their ancient and continuing use is found in the wide variety of names still used for fishweirs: fish impoundment, tidal weir, fishtrap or fish-trap, weir, yair, coret, gorad, kiddle, visvywer, fyshe herdes, passive trapping
Inventing Fish Weirs
Fish weirs were invented by complex hunter gatherers all over the world during the Mesolithic of Europe, the Archaic period in North America, the Jomon in Asia, and other similarly dated hunter-gatherer cultures around the world. Regional differences are apparent in construction techniques or materials used, species harvested and of course terminology, but the basic format and theory is the same world-wide. Fish weirs vary in size from a small temporary brush framework to an extensive complex of stone walls and channels.
Fish traps were used well into the historic period by many groups, and ethnographic information about fish weir use has been gathered from North America, Australia and South Africa. Historical data has also been collected from medieval period fish weir use in the UK and Ireland. What we've learned from these studies gives us information about the methods of fish trapping, but also the importance of fish to hunter-gatherer societies and at least a glimmer of light into the "traditional ways of life".
Fish weirs are best dated by radiocarbon assays on wooden stakes or basketry which were used to construct the trap. Fish bone assemblages from adjacent middens can be used as evidence of use, as can organic sediments such as pollen or charcoal in the bottoms of traps. Other methods used by scholars include identifying local environmental changes such as changing sea level or the formation of sand bars that would impact the weir's use.
- The earliest known fish traps are from Mesolithic sites in marine and freshwater locations in the Netherlands and Denmark, dated to between 8,000-7,000 years ago. In 2012, scholars reported new dates on the Zamostje 2 weirs near Moscow, Russia, of more than 7,500 years ago. Neolithic and Bronze Age wooden structures are known at Wooton-Quarr on the Isle of Wight and along the shores of the Severn estuary in Wales. The Band e-Dukhtar irrigation works of the Achaemenid dynasty of the Persian Empire, which includes a stone weir, dates between 500-330 BC.
- Muldoons Trap Complex, a stone walled fishtrap at Lake Condah in western Victoria, Australia, was constructed 6600 calendar years ago (cal BP) by removing basalt bedrock to create a bifurcated channel. Excavated by the Monash University and the local Gundijmara Aboriginal community, Muldoons is an eel-trapping facility, one of many located near Lake Condah. It has a complex of at least 350 meters of constructed channels running along an ancient lava flow corridor. It was used as recently as the 19th century to trap fish and eels, but excavations reported in 2012 included AMS radiocarbon dates of 6570-6620 cal BP.
- The earliest weirs in Japan are currently associated with the transition from hunting and gathering to farming, generally at the end of the Jomon period (ca. 2000-1000 BC).
- In southern Africa, stone-walled fishtraps (called visvywers) are known but not direct-dated as of yet. Rock art paintings and fish bone assemblages from marine sites suggest dates between 6000 and 1700 BP.
- Fish weirs are also recorded in several locations in North America. The oldest appears to be the Sabasticook Fish Weir in central Maine, where a stake returned a radiocarbon date of 5080 RCYPB (5770 cal BP). Glenrose Cannery at the mouth of the Fraser River in British Columbia dates ~4000-4500 RCYBP (4500-5280 cal BP). Fish weirs in southeastern Alaska date to ca. 3,000 years ago.
A Few Archaeological Fish Weirs
- Asia: Asahi (Japan), Kajiko (Japan)
- Australia: Muldoons Trap Complex (Victoria), Ngarrindjeri (South Australia)
- Middle East/West Asia: Hibabiya (Jordan), Band-e Dukhtar (Turkey)
- North America: Sabasticoook (Maine), Boylston Street Fish Weir (Massachusetts), Glenrose Cannery (British Columbia), Big Bear (Washington), Fair Lawn-Paterson Fish Weir (New Jersey)
- UK: Gorad-y-Gyt (Wales), Wooton-Quarry (Isle of Wight), Blackwater estuary weirs (Essex)
- Russia: Zamostje 2