A few months ago I was intrigued by a post about fishing net design, which got me thinking about trying to solve problems caused by trawl nets (nets dragged along the sea bed). There’s been loads of work directed towards reducing by-catch in net design, but very little regarding trying to stop nets stirring up sediment as they drag across the ocean floor. This is a problem, because it disturbs the sea bed, damaging marine life and coating it in layers of silt, which can kill many species reducing the available food other species need to survive. The end result is swathes of dead or struggling habitat. Recent designs have tried to avoid the doors damaging the sea bed by setting them to trawl mid water and relying on heavy chains to sink the net to the ocean floor, this doesn’t stop damage or sediment being stirred up.
The solution I tried to focus on was making the trawl doors that keep the net apart, self regulate their height, so they keep themselves a set height above the sea bed, no matter the terrain, this means they avoid getting snagged/caught on obstacles and also have very little contact with the sea bed.
I had a go at making a rig, did a few experiments and put together a short video which I hope explains the idea: http://www.producttank.squarespace.com/trawldoors/. Admittedly it has a long way to go with many design changes, before a full scale production piece could be produced, if it would work at all, but it’s an idea. PT