Semi-closed Aquaculture

An evolution of aquaculture

For decades conventional salmon farms have used open net pens. This proven method has produced healthy, low-carbon protein for Scotland and the world for decades. Famers using conventional open net pens must manage and mitigate several challenges. These include fish health issues such as sea lice, environmental disruption, and predator interaction such as from seals.  

At Loch Long Salmon we believe that prevention is better than cure. Semi-closed farming systems improve fish welfare and environmental performance. These systems are already deployed in farms in Canada, Norway and now the Faroes but Loch Long Salmon will be the first company to use them in Scotland.

Loch Long, proposed site of first semi-closed containment farm

Illustration of a semi-closed containment pen

How do semi-closed salmon farms work?

Semi-closed farming systems look much like conventional pens from above. But under the water they have an opaque, impermeable outer barrier that surrounds the fish net.  

Waste and uneaten food cannot flow into the surrounding water, instead gathering at the bottom of the enclosure where it is collected, brought ashore and treated. 

To replace the normal high flow of water through the net, clean, cold water is continuously pumped through the enclosure from deep below the surface. Oxygen is added to the water providing perfect conditions for the farmed fish to thrive.

Sea lice never enter our nets

Sea lice are a naturally occurring marine organism found in oceans and sea lochs. In open net farms juvenile sea lice living near the surface of the water, attach themselves to the salmon.  They can grow and spread to other fish, harming our stock and dispersing into the surrounding environment, affecting wild fish. 

Conventional salmon farmers go to great lengths to control sea lice. This includes chemical treatments, chemical or freshwater baths, physical removal by water jets or brushes, and control by ‘cleaner fish’ which feed on sea lice. 

At Loch Long Salmon, semi-closed systems will circulate water from deep in the loch where sea lice do not live, so they don’t enter the farming system.  Loch Long Salmon will prevent the problem rather than incurring the high cost of sea lice treatments. As a result, there will be no impact to the environment from treatment chemicals nor will wild fish be at risk from sea lice. 

Loch Long Salmon is so confident about the efficacy of the semi-closed system that we will not be applying for a license to use any of these chemical treatments for sea lice.

Trout in Water

Salmon under water