New fishing net wins engineering award

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In early November, the James Dyson Award, worth a total of 20 000 British pounds, went to the inventor and supporters of SafetyNet, a fishing net designed to make trawling more sustainable. The James Dyson Foundation, a charity of British billionaire vacuum cleaner maker James Dyson, runs the international award for student engineers.

Behind the SafetyNet is now-graduated master’s of engineering student Dan Watson, who was inspired by commercial fisheries’ struggle to fish sustainably. He created the fishing net for his final project at the Glasgow School of Art.

SafetyNet’s main innovation is its escape rings, which are reinforcing thermoplastic rings that hold the net’s mesh holes open to allow small and juvenile fish to escape while retaining the larger, targetted fish. In regular nets, the holes typically close up as a result of tension as the trawl moves through water. The small fish that get trapped are then thrown back into the ocean, but are often already dead by that time because of the pressure changes as they are brought to the surface.

Watson began the project in 2008 and submitted it for the James Dyson Award this year. The James Dyson Award includes two cash prizes, approximately C$16 000 each, for the student inventor and their university department.

“Firstly, the prize money will rapidly accelerate the development of the prototypes,” wrote Watson in an email interview with the Martlet. “Secondly, the exposure from the award has meant that people have been coming forward and offering help, whether it’s in the form of testing facilities or even the use of a trawler. That will massively affect the speed at which the project can move forward.”

The World Resources Institute (WRI) says one billion people, mostly in developing nations, rely on fish as their main source of animal protein. But today, more than 70 per cent of the world’s fisheries are either fully exploited or depleted. WRI, along with other research institutes and departments, like Fisheries and Oceans Canada, warn that without sustainable fishing methods, oceanic fisheries won’t be able to match our growing demands for fish.

Watson consulted with fishermen and industry experts and looked at fisheries research for ideas.

“Most of the research was based on experimental observations from around 30 years’ worth of work done by different fisheries institutes around the world,” wrote Watson. “The interviews brought some of the industry issues to light, and the research helped find physical and behavioural phenomena [in fish] that might aid in trying to solve those issues.”

For example, he learned that cod, which are endangered, tend to swim towards the seabed to hide when under threat. Other fish, like haddock, which are more plentiful, swim upward when stressed. With this in mind, Watson made the net so that the top half is fine mesh to stop the marketable fish from escaping, while the bottom half is large mesh to allow the endangered cod to escape without injury.

The very end of the net, which is shaped like a long, narrow cylinder trailing behind the bottom half of the net, is where the fish are retained and is also where the escape rings are placed, allowing the small haddock (and other fish that exhibit similar behaviour) to escape. The rings are illuminated so the fish can see there is an exit.

Philip Dearden, professor and chair of UVic’s Department of Geography, raises one concern about the SafetyNet: it could exacerbate the problem of fish getting smaller through contemporary evolution as we wipe out the larger fish.

“Big fish may differ genetically from small fish. As we wipe out the big one, we remove their genes from the reproductive pool,” he wrote in an email interview.

Dearden says larger, older, female fish have a higher reproductive capacity. He cites the Big Old Fat Fecund Female Fish (BOFFFF) hypothesis, which states that by letting smaller fish escape, we are selecting for smaller fish with lower reproductive potential.

“The BOFFFF suggests that these are the very ones we should be saving, not preferentially hunting,” wrote Dearden of the larger fish.

When asked about his thoughts on this theory, Watson said he hadn’t heard of it before but is willing to look into it.

“The aim is to release juvenile fish, whether they are from a larger or smaller species, which could eventually grow to become large fish,” wrote Watson.

“The net may work in some fisheries . . . but it is not an answer,” wrote Dearden. “Just fish less. That’s the answer.”

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