Aboriginal fish trap, South Australia

Sticks and stones: locating an unusual fish trap at Lake Alexandrina

Text by Scott Heyes, August 2008

A number of archaeological and cultural sites of Aboriginal and non-Aboriginal significance are appearing on a daily basis along the shoreline of Lake Alexandrina. One such feature, an aboriginal fish trap, was discovered on the northern shore of the Lake by a pastoralist in summer 2008. The stone and timber arrangement pictured is among a network of other types of fish traps that have since been discovered along the retreating shorelines of the neighbouring Lake Albert system as well.

Starved of water for some years, the Lower Lakes have dropped to levels not seen since the early 1900s, when the wetland systems of the Murray River were reclaimed. The retreat of these water bodies has even surpassed the levels that were typical before barrages were built on the Murray in the 1940s, which subsequently altered the natural flow regime of the Lakes.

The Aboriginal custodians of the Lower Lake systems are beginning to familiarise themselves with fish traps like the one featured, most of which have not been seen several generations. Preserved and covered by the water for more than a century, local Aboriginal experts have described to me how they believe the fish trap functioned. Their knowledge is based upon oral history of fishing techniques and practices that were particular to the region. Complemented by information on Aboriginal fishing techniques in ethnographic reports for Lake Alexandrina, and based on fieldwork and interviews with local fishers, it is possible to suggest how the fish trap functioned.

At the time the fish trap was built, the main catch was saltwater fish such as mulloway, mullet, flounder, bream and garfish. Lake Alexandrina was affected by the ebb and flow of the tides, as well as seasonal river flows. During flood periods, saltwater fish withdrew from the Lake and were replaced by freshwater fish such as Murray cod, callop, catfish, congoli, and silver perch. The trap was designed to catch either freshwater or saltwater fish, and it is believed that shellfish were placed inside the trap at times as an attractant.

It is reported that the Aborigines of the Lower Lakes made “stick pounds” in the 1840s to capture large quantities of fish for the Adelaide markets, although it is not known whether the Lake Alexandrina fish trap was constructed for this purpose. The size of the fish trap suggests that it was built for domestic rather than commercial purposes. Archaeological surveys are currently underway to determine the approximate age of the fish trap.

Situated approximately 150 metres from, and perpendicular to, the current-day shoreline, the fish trap consists of two parts – a limestone entrance way spanning 2.3 metres and an adjoining timber pound with dimensions of about 2 metres long by 1.5 metres wide. The 42 native-pine (Callitris sp.) posts that form the pound, with an average diameter of 125 mm, appear to have stood about 700 mm high and were driven about 500 mm into the mud. It is believed that a removable covering of rushes and reeds on a light timber frame was placed over the pound to prevent birds from spooking and eating the trapped fish.

Three layers of flagstones were stacked atop each other along the entrance way to a height of about 500 mm. Beyond the flagstone entrance way are six posts that extend some 13 metres along one edge and three posts that extend about 9 metres along the other. It is believed these parallel posts formed a framework upon which the aboriginals strung their mesh nets. The short spans of about 2 metres between each post would have enabled their nets to remain taut. Walls of reeds and rushes might also have been created between the posts to form an impervious barrier. If nets were employed, the fish moving upstream on the incoming tide would have either been meshed in the nets or trapped inside the timber pound if they swam along the nets.

Two or three large rocks were placed at the junction of the timber pound and stone entrance to a height of about 400 mm. This would have enabled fish to swim into the pound and yet be trapped once the tide ebbed. A pre-formed basket or pouch of netting is thought to have been designed to fit between the three parallel posts that lead out from the flagstone entrance, a width of 360 mm. With the basket or pouch in place, the rocks were removed at low tide and then the fish flushed out. Fish that were too large to be captured were speared.

The middens and fire sites that are located on higher ground near the fish trap, which bear fragments of fishbone, suggest that this site was a popular and productive fishing ground. As the Lake continues to dry up, the fish trap is now exposed to the elements and is subject to rapid decay and weathering. A watery world no longer offers it protection. Only a short window is available to investigate and learn from this archaeological feature. The rarity and uniqueness of this fish trap as one of the few surviving examples of timber and stone arrangements in Southern Australia might only persist for a few decades, but it has nonetheless provided further information on fishing and construction techniques that were used by previous generations of Indigenous people.

In this project we generated a 3D animation in 2008 of the fishtrap to demonstrate how it might have functioned. The stillshots below have been taken from this animation.

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