8 Cooling and Energy Saving

This case study presents an overview and examples of engineering of alternative food collection and storage solutions focusing on fish traps.

The Fish Traps on the outskirts of Brewarrina on the Bardon River are considered one of the oldest human made structures and the site is heritage listed (DCCEEW, 2021). They can be visited when in the region (Brewarrina Tourism, 2021). They show an ancient way of collecting and storing fish in the ponds, and they have been also linked to aquaculture in the area. The care of the fish population along the river was supported by regular knowledge sharing ceremonies in Brewarrina.

The Brewarrina Fish Traps are known as Baiame’s Ngunnhu, as the creator spirit Baiame created these traps by throwing a net across the river and, with his two sons Booma-ooma-nowi and Ghinda-inda-mui, built the fish traps to this shape. They are a complex network of dry stone walls of river stones arranged in ponds that catch fish as they travel upstream before breeding. Channels between the ponds allow some fish to continue up or down stream to avoid overfishing.

The fish traps reflect a simplicity of design, which was adaptable to the seasons and changing water levels. The traps higher up the banks were used in times of flood and the ones in the main river flow were used as the water dropped. The fish traps and the technology behind them show similarity to other natural approaches.

The stories of their creation, and the Aboriginal Law governing their use, are a significant spiritual, social and governance aspect of Aboriginal society, and important in the trade relations between Aboriginal groups from the entire region. The fish traps were an important site where food could be stored while people stayed to talk about land and water management and arranged marriages.

In the 1920s, non-Aboriginal people living in Brewarrina carted the stones away that had formed the fish traps and used them for foundations for buildings in the township. A weir was built across the river in the 1970s that again took stones from traps and also interupted the sediment flow and ecology in the river.

For instance the native fish could not move up the fishway built up the sides of the weir as it was constucted at an angle too steep for these fish to swim up. After more than 160 years of destruction of the traps and with loss of traditional management and maintenance due to people being forced into a mission and denied their traditional activities, there are still substantial elements of the fish traps in the river which the local Ngemba people continue to maintain along with the knowledge of their use and maintenance. The stories of the significance of the traps to people in the area are still told.

Below are old (pre 1970’s) and a recent image of the traps.

Sustainability

The traps are built as dry stone walls (ie no mortar) and can withstand high floods. A locking system made from the river stones fixes the base of the trap to the bed of the stream, while the keystone type structures provided more strength through the transversal forces of the heavy stones. They are designed with the small opening facing downstream.

As the fish swim upstream they enter the traps and are stopped at the top end. The trap can then be closed, or the fish can be caught by hand or spear and tossed into smaller ponds at the end of the trap for storage until needed. The traps are scattered across the river, not entirely blocking the passage of fish, but some in the centre flow for when levels are low, and some higher up the banks to work during floods.

Fish Traps around Australia

There are also many salt water traps along the sea coast. A survey of Queensland waterways in 2011 found 179 fishtraps and weirs. This research has been done to locate some of the traps in Queensland, the Gulf of Carpentaria and the Torres Strait with the hope of preserving them (Rowland & Ulm, 2011). These were stone-walled and intertidal to control the coming and going of marine animals.

The methods of construction, maintenance and use of the traps were shared with the community to ensure their ongoing use by people living in the region and sustainable use of resources. Some were made of rock, which had to be reset after high seas or river floods. Other were made of sticks and were set up when needed, and allowed to be re-incorporated or decompose into the surroundings when not needed, such as Figure 5 showing a wooden fish trap. The woven trap will be positioned in the gate when the tide turns and water begins to flow out, found at Bulgai Plains, between Liverpool River and Tomkinson River, Arnhem Land, NT, 1978.

Various other additions and adaptions have been seen at times, and the use of new technology and material that came with colonisation was adapted to reinforce the traps or made collection ponds out of rings of corrugated iron.