The flow-through facility has been fitted with five new 8m tanks which replace a number of smaller tanks, enabling a better outcome for the fish as well as increased capacity and greater flexibility in smolt productions.
The new tanks, which replace smaller outdoor 3m tanks, are housed within a large polytunnel with a dark cover so light can be controlled – a significant enhancement for fish welfare while also providing weather-proof working conditions.
Head of Freshwater Rory Conn said Knock can now produce 1.5 million smolts annually, complementing production from the RAS (recirculating aquaculture system) hatcheries at Barcaldine and Girlsta, in Shetland.
‘The changes at Knock have been comprehensive and allow us to produce more smolts at the size we want, at the appropriate time for stocking our marine sites, and to do that in a more cost and environmentally efficient way.
‘Scottish Sea Farms’ strategy is to have larger, more robust animals going into the sea and that is equally applicable for Knock as it is for Girlsta in Shetland and Barcaldine. In recent years, we’ve more than doubled the average smolt size, as a company and out of Knock.
‘The development on Mull has also given us much greater flexibility throughout the cycle. The plan here had been to move away from egg production and take in fry at around 3-5g from the recirculation hatcheries at Barcaldine or Girlsta where we have greater ability to manage temperature.
‘But with egg availability being constrained at certain times of the year, which pressurises incubation capacity on all sites, maintaining egg incubation and first feeding capacity at Knock is important to ensure we can produce the smolt numbers when they are required.
‘Repurposing tanks, space and heat recovery infrastructure has been very CapEx efficient and provides production flexibility at a lower operating cost, relative to what was on site.’
Rory credits long-time Knock Manager Ian Fraser with reimagining the new hatchery configuration to enable a steady supply of smolts.
Ian, who celebrated 38 years with the company in April, said repurposing some of the old tanks and installing an upgraded water supply and heat recovery system provided a more energy efficient environment for the incubation unit.
‘The hatching and first feeding stages require more heating and it tends to be less economical to heat water in a flow-through unit than in the RAS at Barcaldine, where water is used multiple times.
‘But when we took the old tanks out, we repositioned eight of them in the back of the shed and, with the new water system, we now have first feeding capacity for up to one million fish.’
The development, which did not disrupt production at Knock, is now complete and the freshwater team is finding it easier managing the bigger but fewer tanks, said Ian.
‘Repurposing tanks, space and heat recovery infrastructure has been very CapEx efficient and provides production flexibility at a lower operating cost, relative to what was on site.’
Local contractors supplied the tanks and Scottish Sea Farms’ Senior Freshwater Engineer Stephen King and regular contractor Archie MacKinnon oversaw the works.
