Project Python Aims to Lock Seals Out
The South East Trawl Fishing Industry Association (SETFIA) represents fishers, quota owners and wholesalers who have an interest in the Commonwealth Trawl Sector (CTS). The fishery is the main supplier of fresh local finfish in Australia with most sales through Melbourne and Sydney fish markets.
Seals enter trawl nets to feed on fish. Some seals then become disorientated and can’t find their way out. Seal catches (interactions) are becoming harder to avoid as seal populations increase. Many seals are released alive, but the industry wants to stop interactions and is acutely aware that the Australian community feels the same. Australian law requires that all seal interactions be reported.
Using funding from the Australian Fisheries Management Authority (AFMA), SETFIA engaged Dr John Wakeford, a fishing gear specialist with experience in mitigating trawl risk to marine mammals. His brief was to develop a device to reduce seal interactions.
A trawl fishing operation has three stages: shooting the net, fishing, and hauling the net. It is likely that seals enter the net as it being hauled toward the surface – that is when fish are in the net and seals are attracted to enter and feed. Seals are also unlikely to spend much time at fishing depths (200m-1,000m) further suggesting that seals mostly enter the net as it is hauled. The project aims to find a way to allow skippers to close the net in deep water as it is being hauled to prevent seal ingress.
This was achieved in trial conditions with the release a sea anchor; water pressure on the anchor tightens a rope around the body of the net, which in turn prevents seal ingress.
The 3 minute video shows footage of a half-scale model of a demersal trawl in the Australian flume tank in Tasmania. The tank simulates a trawl net while fishing using a conveyer belt and water flow to simulate the drag of water and the seafloor on the net. In this test the sea anchor is manually released and successfully closes the net preventing ingress of marine mammals. The next stage of work is focused on developing a device that sends an acoustic signal to the net releasing the sea anchor to constrict the net.
Article source: https://mailchi.mp/setfia.org.au/projectpython