Friday, 4 October 2013

Return to Camas Glas

Rosie Curtis, the manager of the Marine Harvest fish farm at Camas Glas, invited us out to visit the salmon we'd seen arrive as smolts back in March - see posts here and here.  Our visit coincided with another key stage in their lives - the grading.  This takes place after seven months in the cages, and the process is carried out by this grading machine which is towed from farm to farm on a raft.

We were there to watch them process one of the cages.  Before we arrived, all the salmon in the cage had been trapped in a net, held up by yellow buoys, which could slowly be reduced in size as the salmon went into the grader.  And what a difference there is in the fish since we last saw them.  The biggest is now nearly two kilogrammes, and they all look in superb condition.

The fish are held within the yellow buoyed area '1'.  They are drawn up into the blue pipe, '2', by two huge pumps, '3', which also pump them upwards through two pipes, '4', into the top of the grading shute, '5'.  The fish are sorted into three grades within the shute with two grades, small and medium, being returned via the black pipes '6' to the original cage, while the larger fish, which are over a kilogramme in weight and make up about a third of the salmon, go into a floating cage beyond the raft.  This will transport them to one of the other fixed cages.

John MacRae is in charge of the raft and spends about a fifth of his time moving between Marine Harvest's six farms in Lochs Linnhe and Sunart, helping with the grading.  In his spare time, John is a member of Lochaber Mountain Rescue team and a keen participant in ben races.  For anyone unsure of what a ben race is, the website for the annual race up Ben Nevis is here - and John's in the 'Results List'.  At 50, he's just completed his 25th race.

In the picture, John is standing at the top of the grading shute.  As we watched the fish start to come into it, Ferguson Transport's Harvest Caroline II was arriving to deliver 50 tonnes of fish food to the farm.  At one time this food was processed from fish, now it's 75% vegetarian, being largely made from vegetable oils, beans and maize.

John can adjust the gap between the longitudinal bars in the shute for different grade sizes.  The smaller fish fall through to be returned to the cage while the bigger ones slide to the bottom of the chute, to be piped into the mobile cage.  It may look a bit violent, but it's nothing to salmon which, in their natural habitat, swim up and down waterfalls and rapids.

This view looks at the pipes which lead the fish back to the cages, with deputy manager Calum MacPhail looking on.  But there's one further thing this machine does.  It separates off another fish which now lives with the salmon....

 ....a local wrasse.  These small fish are a new idea, and they perform a very important function - removing the sea lice which, until recently, were killed using chemicals in a process which attracted some criticism.  One local farm has completed a cycle with its salmon using only wrasse to control the lice.  The wrasse are caught by local fishermen and encouraged to stay in the cages by being treated like fish kings.

Rosie Curtis showed us their accommodation, which hangs down in the cages and is designed to give them small platforms on which they can rest while, at the same time, making them feel at home by looking like fronds of kelp.  The wrasse do such a good job in eating all the lice that they have to be fed a supplement, made from crab and mussel.

Salmon farming is a growing and very successful industry in Scotland, being worth some £530 million to the economy.  Something like 78% of the product is consumed in the UK, but more and more is going abroad, with China a big customer.

In February the first of the salmon from Camas Glas will be on their way to market, and by the end of next year, the cages will be empty and ready for the next batch of smolts.

Many thanks to Rosie, Calum and John for giving their time to explaining everything to us, and to Marine Harvest for allowing us to visit Camas Glas. 


  1. Dave McFadzean Moniaive4 October 2013 at 19:20

    It's a real pity they hadn't found out about the wrasse before they went and decimated the west coast sea trout stock. I used to catch braw sea trout off the rocks at Sanna absolutely infested round the head with sea lice. Now the sea trout are very scarce in areas frequented by fish farms. Sad really but this new chemical free method might hopefully lead to some kind of recovery.

  2. There is a scientific lab around the other side of Ardnamurchan, at Ardtoe, that I believe is heavily involved in the wrasse process. Would be an interesting blog article. There are also hundreds of young Wrasse off the outflow pipe there.

  3. Yet again a fascinating article. Thanks Jon
    Especially about the Wrasse.
    I do hope this works to make salmon farming chemical free all over the UK.

    Hooray... think I managed security code today!

  4. Fascinating, thanks for posting. I've always been rather ignorant about the actual workings of this very important industry but am now considerably enlightened.