Mowi Hatchery tour
Benefits ‘great’ at state of the art RAS hatchery that supplies half of farmer’s juveniles
OPERATING a recirculating aquaculture system (RAS) is, to some extent, like playing Mother Nature, said the manager of Mowi’s Inchmore hatchery in Glenmoriston. ‘It’s like an aquarium; you’re controlling everything that nature does anyway,’ said Matthew Paget.
Mowi’s approach in its latest RAS facility, which was officially opened by Scotland’s rural economy minister, Fergus Ewing, in the summer of 2018, is to leave nothing to chance.
‘The hatchery is deliberately over engineered so if there is a disease outbreak we can isolate that area,’ said Paget.
But such is the focus on biosecurity at Inchmore, one of the most sophisticated RAS systems in the world, that all possible parameters are managed and monitored to prevent pathogens entering in the first place.
The system was built by International Aqua Tech (IAT), which has also recently completed Mowi’s Anglesey wrasse plant, due to open this month. An aquarium specialist, IAT worked closely with Mowi’s freshwater manager and recirculation expert John Richmond.
The £28 million, 13,500sq m (about two football pitches) hatchery employs 15 full-time staff and has two or three engineers on site every day.
It has back-ups at every stage of production, with four RAS systems for egg and alevin incubation, and four systems for the fry and smolt, Fry A and B and Smolt A and B.
Most of this, along with the grading and vaccination area and the filtration system, can be observed from the visitors’ gallery.
This glass encased corridor, accessed directly from the foyer and running almost the entire length of the building, enables visitors to experience the hatchery operation without going through the disinfection procedure.
From here, Paget explained the Inchmore
production process, which is geared to provide 800 tonnes of fish annually- up to six million parr and six million smolts, produced in four batches a year.
This amounts to half of Mowi Scotland’s young salmon, with the rest coming from its sister site at Lochailort or a smaller, flow-through hatchery in Ullapool, which produces about four million fish a year.
Inchmore, like Lochailort, was designed to increase Mowi’s smolt production as it develops new sea farms and expands the business.
Some of the salmon from Inchmore will go directly to Mowi’s sea pens and others to freshwater lochs for further on-growing.
‘As a company, we can’t produce all our smolts just through the ‘recircs’, we don’t have enough capacity,’ said Paget.
‘But what we do use is freshwater loch sites to grow biomass.
‘We produce 10-12 million a year and from that, say five million will smolt on site and the other six or seven million will go out to freshwater loch sites (Loch Garry, Loch Ness, Loch Shiel which is known as Glenfinnan, Loch Arkaig and Loch Lochy).
‘They have various biomass limits and will do 10 million smolts and we (between here and Lochailort) will do the other 10 million or thereabouts.’
The Mowi production team knows from the beginning which fish are going to which sites, what weeks they are going to be transferred, and more or less the size they are going to be.
‘We will have a constant trickle going out to the freshwater, and a constant trickle going out to seawater,’ said Paget, who has overseen the Inchmore operation since October 2018.
‘It’s all planned. We have growth models and predictions that we’ve developed over the past 40 years. Production managers will sit down and work out what sales require and it works from the top down.
‘They then say how many smolts are needed for seawater, and they will be produced from the freshwater cages and the recircs.’
Maintenance
On the morning of Fish Farmer’s visit, parr weighing around 100g were being transferred, via pumps, into tanks on board a Solway Transport lorry, destined for the freshwater loch at Glenfinnan. They will have a brief stay there before being put out to sea in the spring, at around 130-150g.
The smolt tanks (nine each in the two units, Smolt A and B) are now empty – but not for long. They will be stripped down for maintenance work before receiving the next batch of fish in about four weeks’ time.
Paget said the tanks, 12m diameter and 3m deep, are made of concrete with an epoxy polyurethane lining. They can hold up to 160 tonnes of smolts, which is 140,000 fish of 150g, but normally run at 125 tonnes in a smolt unit, around 120,000 to 150,000 fish per smolt tank. Fish of 150g will go straight out to sea pens.
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The hatchery is deliberately over engineered so if there is a disease outbreak we can isolate area” that
‘By that point, you have about 45 kilos per cubic metre; at the recirculation units, we can go up to 50-60kg/m3 under RSPCA standards but usually take them to 45kg. The maximum at sea sites is 15-17kg per m3.’
Fry A and B each have 15 tanks of 50m3. Both Fry A and Fry B are currently stocked with fish of around 25g, which will be grown until they are vaccinated – at about 45g- in four weeks’ time, then they will be transferred to the smolt tanks.
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We’re always looking at better ways to clean the water and to disinfect it and it” sterilise
‘The fish will be kept in the smolt tanks until they are ready to go to sea,’ said Paget. ‘We’re doing all the freshwater stage here with these ones.
‘In order to smolt the fish, we put them on to five to six weeks ‘winter’ (550 to 650 degree days); this is 10 hours light, 14 hours dark. After this we ‘spring’ the fish, using 24-hour light for 350 to 450 degree days (usually three to four weeks in the recirculation units).
Control
Paget spent five years working at Mowi’s RAS hatchery at Lochailort and also had spells at both the old plants at Inchmore and Lochailort. Before Mowi, he was involved in the Kielder hatchery in Northumberland which restocks the Tyne.
He is well aware of the advantages of being able to control every aspect of production in a land based RAS hatchery – and the risks.
‘Temperature controls growth so what happens here is we can control the temperature, we can heat and chill the water, and we also control PH…it’s not 100 per cent accurate but we can grow the fish to within a couple of grams of the predicted model.
‘If you get a virus or disease, it becomes like a nutrient broth because you’re just circulating the same water round and round. This is the reason why we try our utmost not to get disease in the recirculation units.’
Each fry unit can circulate 2,680m3 per hour, while each smolt unit can circulate 4,690m3 per hour, which equates to 14,740m3 per hour through all the systems combined.
Some 17.7 million litres (seven Olympic size swimming pools) of water circulate through the RAS system at Inchmore per day, a vast volume that is 90-95 per cent recirculated.
‘The old flow through site used 500 litres a second to produce 30 to 50 tonnes of fish,’ said Paget. ‘We extract 70 to 100 litres per second to
produce up to 800 tonnes – we’re much more efficient.
‘In a flow through, clean water is coming in from the river all the time so you’re flushing it out. In a recirc, the idea is not to get the disease in the first place.
‘Everything is disinfected. We fill up 700m3 tanks with river water, and then we ozonate it until it’s basically sterile. Then it’s moved into a storage tank and only then can it move into the units.
‘There is no environment you’re going to be 100 per cent sterile but you minimise the risk as much as you can.’
Inchmore suffered a setback soon after its official opening when a fault occurred in the system delivering oxygen, causing the loss of about three per cent of the stock- some 500,000 fish at 80g weight.
‘That was a mechanical teething problem – the oxygen tower had a serious fault.
‘We’ve just been lucky that that’s never happened in Lochailort,’ said Paget, adding that Lochailort has a back-up oxygen tank so such a risk was reduced at that site.
‘It’s very unlikely that it will happen again but there’s no reason why something else can’t go wrong, like all fish farming.’
Post-smolt
While RAS has been shown to work for juvenile production, Paget is less convinced about the merits of full scale land based salmon farming.
‘I don’t know if it’s viable financially long-term. I think you’re paying a lot of money on inputs for something nature does for you already a lot cheaper.
‘With these [juveniles], the inputs are massive, but the benefits are great. When you scale that up, your inputs are scaled up too. Whether that is sustainable is a very tricky question to answer.
‘This site only produces 800 tonnes maximum a year. A small average sea site is doing between 2,000-5,000 tonnes – so basically eight or nine times bigger to produce the same.
‘This site is not far off £30 million to build…so you’d need eight or nine
“The pumps have evolved over many years and are designed to be run all day, every day”
times that cost. And space at sea is not an issue but space on land is.
‘I know we’ve done it, Denmark has done it, but it’s expensive and it’s not always reliable. If it was easy, we’d have done it by now!’
Operating expenditure at Inchmore is between £7 and £9 million a year, said Paget, although the infrastructure is built to last.
‘Most of the fittings will last indefinitely, probably longer than us.
‘The pumps have evolved over many years in the water treatment industry and are designed to be run, like in an aircraft jet, all day every day.’
But Mowi has a development budget and is always open to innovation, especially in the recirculation systems.
‘We’re always looking at better ways to clean the water and to disinfect it and sterilise it, and find cheaper and more efficient ways of doing it,’ said Paget.
Mowi works with research organisations, such as SAMS in Oban and Nofima in Norway, to develop a greater understanding of the impacts of recirculating water on the physiology of fish. In particular, they are investigating the influences of water chemistry on smolts.
‘We know that they are more sensitive to ions in the water because their gills are changing, so we find if we have large amounts of dissolved phosphorous in the water we need to find ways of combating that,’ said Paget.
‘We don’t fully understand the impacts of it, we just know that sometimes smolts from the recircs going to seawater can have slightly more mortality, compared to stocking from freshwater lochs, and we know it’s something to do with the water chemistry and its impacts.
‘It’s quite a minor issue in the grand scheme of things, but it’s trying to ever better ourselves. Normally, we’ll have one or two per cent mortality post transfer, when in reality you’re looking for .1 or .2 per cent.
‘If you go back 10 years, five per cent mortality was good at sea transfer, so it’s all about improving.’
Rising water temperatures, which can increase sea lice levels and exacerbate disease challenges, may be a key driver in any decision to grow bigger smolts on land.
In fact, the possibility of Mowi siting a post-smolt plant on Skye was mentioned during Fish Farmer’s first visit to Inchmore in 2017.
Faroese salmon farmers have been putting smolts of between 500g and 2kg to sea for some time, and Mowi opened a post-smolt plant in the Faroe Islands three years ago.
‘There are massive environmental benefits,’ said Paget. ‘If you reduce the biomass you put into the sea pens and you also reduce the length of [on-growing] time, the fallow periods can be increased, which would reduce sea lice, which would reduce gill amoebae.
‘Also, it would reduce the amount of treatments you use. But these sites are expensive to build and expensive to maintain.’
For now, it is Inchmore that is the state of the art in Scottish hatchery production.
As John Richmond said at the site’s opening nearly two years ago: ‘Over 12 million fish will start their lives here and I hope that what we have provided will be a comfortable home for them before they move on to our seawater production facilities.’