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Waste capture system could help Scottish salmon sector grow

The waste capture system is being trialled on square pens and will be adapted for circular pens too
The waste capture system is being trialled on square pens and will be adapted for circular pens too

An Inverness based company has developed a waste capture system that reduces deposition under fish pens and could enable farmers to increase their biomass in inshore locations.

The system, created by Rodger Taylor of Aqua Innovations, is retro fitted to existing pens, collecting waste (uneaten feed and faeces) as it drops out of the water column. The waste is then pumped to the surface where it is treated and disposed of.

Taylor, a pioneering aquaculture innovator, has teamed up with Northern Light Consulting of Fort William to help commercialise his scheme. A £250,000 grant from the UK government’s Seafood Innovation Fund has financed the design, construction and testing of prototypes.

He hopes his invention will help Scotland’s salmon sector to grow by enabling inshore sites to become more productive, and not restricted to biomass limits imposed by SEPA (the Scottish Environment Protection Agency) based on deposition.

Hostile environment

‘I’ve argued that going offshore is exactly the wrong thing to do because all you’re doing is going to a more hostile environment, everything gets bigger and heavier and there’s no guarantee that your equipment’s not going to fail and there’s days when you won’t get near the sites because of the weather,’ he told Fish Farming Expert.

‘What we should be doing is utilising inshore sites that previously have been licensed but which we can’t use for various reasons. If you put waste capture in, then you can open up these sites.’

The system, made from an MDPE (medium density polyethylene) frame supporting a tailored tarpaulin that covers the bottom of the net, has proved effective so far.

Waste is funnelled into a cone then pumped up to a filter bag on a feed barge or pontoon, with the liquid draining back into the water and the solids transferred to land.

Circular cage

Wester Ross Salmon conducted initial trials on its square pens and now Mowi is testing the system on square cages at its Ardnish test site at Lochailort, while trout farmer Dawnfresh is due to trial a circular cage version in Loch Etive.

‘With circular cages, it would be much better if we incorporate a new mooring design because I believe the moorings from the cage need to work in conjunction with the moorings from the waste capture system, so that as the tide moves the cage it also moves the waste capture system, so they work in unison,’ said Taylor.

Read more about Aqua Innovations’ plans in the current online edition of Fish Farming Expert magazine.