Gained better control and reduced lice infestation
Subsea feeding and lights that makes it more attractive for the fish to stay in deep water have contributed to reduce the amount of lice to far below critical level at Marine Harvest’s Rogne location.
When the sea is calm around the cages at Rogne and the sun casts its light over the majestic Sunnmøre Alps, you can be easily fooled to believe that Operations Manager Svein Olav Otterlei has an easy job. But the strong sea current in the waters outside Ålesund poses some challenges, especially when it comes to feeding.
“Gaining better control was our primary reason for trying subsea feeding. With regular surface feeding, strong winds and sea currents will namely lead a substantial amount of feed out of the cages,” Otterlei tells.
Therefore, the operations manager and his team now only uses surface feeding during the adaption phase. As soon as the fish is ready for 9 mm pellets, they will switch to subsea feeding. Less feed wastage is just one of the advantages, tells operating technician Svenn-Even Otterlei, who pays careful attention to the surveillance images from the facility’s nine cages.
“Here’s a cage with a subsea feeder from AKVA group. I’m very happy with how well it spreads the feed, which makes it a lot easier to monitor the fish during feeding. This has given us confidence to increase the feed amount compared to when we only used surface feeding,” he says.
Rogne is situated outside the island of Longva, not far from Ålesund.
The Rogne teams sees clear advantages of keeping the fish in deeper waters. Therefore, they have combined subsea feeding with subsea lights. AKVA group’s AKVA Aurora SubLED Combi, which has both blue and green anti-maturation lights, white contrast light and photo tactical UV lights in the same unit, is one of the lamps they are using.
“As of January 10th, we have controlled the entire biomass with lights. We have closely monitored the fish’ behaviour and found that there are hardly any fish in the sea layers above the lamps,” says Svein Olav Otterlei, who is very satisfied with the results.
“Before we started actively controlling the biomass with lights, our lice count was three times as high. The lights have contributed to reduce the lice amount to way below critical level. I’m also happy with how easy the combi lamps are to handle and that there is hardly any fouling on them. That makes the maintenance job a lot easier.”
Operations Technician Svenn-Even Otterlei is carefully watching the feeding.
With subsea feeding and subsea lights, the operations manager at Rogne believes he has a found a recipe that works. Better control with the actual feeding, and fewer feeding interruptions due to reduced lice treatments, is positive for improved feed rate. Nevertheless, he is clear that the technology, especially when it comes to subsea feeding, may still be improved.
“We need to solve some challenges that can make the maintenance work easier for the customer. The cooperation with Svein Olav Otterlei and Marine Harvest is very valuable to us, as they are careful to document their results. This gives us important feedback on what we can improve and not least a confirmation that our systems are working as intended,” says Bjørn Sirnes and Guttorm Lange, who works with sales and development of lights and subsea feeding in AKVA group.
Marine Harvest has two subsea feeders from AKVA group at Rogne. From the cyclone on the surface, the feed is distributed through 12 nozzles approx. six metres below the sea surface.