E!12004 Ultrasonic and physical elimination of Caligidae sea lice from salmon fish farms

We will develop a sea lice control system that supplies oxygenated and clean seawater to sea cages, and eradicates at least 95% of sea lice by physical filtration, ultrasonic cavitation and skirt exclusion. The outcome will be a scalable, flexible prevention system that eliminates the need for chemical or thermal control, improves fish health and welfare, accelerates biomass growth, and increases fish farm productivity and profitability. In 2019 -20, five main activities are performed: 1) Performance of 4-5 different pilots of the air-lift pump system is conducted at 2-3 commercial cage sites. The following components/operations are emphasized: - Foldable funnel - Suspension/floating unit - Bottom weight - Diffuser system (optimizing the water transport) - Mooring system - System for hauling Besides, different lice skirt are developed/tested for improved stiffness/stability in sea and more robust suspension and bottom weight. 2) Lab-scale tests at The Western Norway University of Applied Sciences of ultrasound (US) effect on mobile stages of sea lice. High power US demonstrated the highest killing rate where 60% lice mortality was demonstrated over 24-hour treatment. Lower power US, reduced exposure time (21 h) and less UV coverage (90 vs. 360 degrees) resulted in lower killing rate. 3)Monitoring of gas concentrations in sea water cages at Salmar's fish farm, site Gjerde, Aure. A cage shielded by lice skirt and stocked with salmon was supplied deep water by a newly developed air-lift pump concept (Oxyvision AS). Pumping of deep water demonstrated significantly higher diss. oxygen concentration in the water column compared to a similar cage without deep water supply. 10-15% increased oxygen concentration and low risk of gas supersaturation (TGP)in deep water supplied cages represent highly improved conditions and thus better growth and fish welfare (salmon performance not included in this test). 4) Lab-scale tests of oxygen transfer rate of diffuser hoses with different punctuation and air flow. The tests clearly indicated improved transfer rate at low punctuation (low hole density) and reduced air flow rate. Similar tests were performed to optimize the size of diffuser holes for pumping of water by air-lift. 5) During a 3-month period (Oct 2019 - Jan 2020),monitoring of oxygen concentration and some key production parameters (appetite, mortality and lice counts)was conducted in cages stocked big salmon (> 3 kg) at a farm in Northern Norway, Western Finnmark. In one cage shielded by lice skirt (10 m)deep water was pumped by air-lift (concept: Oxyvision)while the surrounding reference cages (4 - 6 cages)were managed without lice skirt/deep water pumping. The reference cages removed the lice skirts in October due to low oxygen concentrations. Deep water pumping in the skirt shielded cage caused a stable oxygen concentration above 7 - 8 mg/L at 5-10 m depth throughout the period, i.e. more or less at the same level as in the open reference cages. Periodical suboptimal oxygen drops observed in some open cages were less pronounced in the cage supported oxygen-rich deep water. The favourable conditions in the "trial cage" (skirt/water pumping)resulted in low mortality and a consistently high appetite of the fish stock. (Accurate measurements of growth rate and feed utilization not available). Weekly sampling indicated no notable louse infestation differences between the trial cage and the reference cages.

Signifikant redusert overlevelse av lakselus ble ikke påvist før etter flere timers eksponering med ultralyd. Forsøket viser at anvendelse av ultralyd bør kombineres med andre tiltak, fortrinnsvis ved tiltrekning av lus med kunstig lys, for å kunne oppnå høy effekt i laksemerder. I prosjektet er utviklet et effektivt pumpesystem for løfting av dypvann i merder som anvender luseskjørt. De gjennomførte testene viser at systemet forebygger risiko for ugunstig oksygensvikt og medfører økt vannutskiftning i merdene. Dermed opprettholder fisken god appetitt og vekst. Pumping av vann ved anvendelse av luft (air-lift) er energibesparende sammenlignet med andre pumpesystemer. Kombinasjonen luseskjørt og pumping av dypvann er et viktig bidrag til kontroll av lusesmitte samtidig under gunstige miljøforhold. Anvendelse av ultralyd i merder omgitt av luseskjørt vil kunne øke beskyttelsen mot luseangrep men ekstra tiltak for tiltrekning av lus ved ultralydkilden er nødvendig.

CaliSonic project will develop a sea lice control system that supplies oxygenated and clean seawater to sea cages, and eradicates at least 95% of sea lice by physical filtration, ultrasonic cavitation and skirt exclusion. The outcome will be a scalable, flexible prevention system that eliminates the need for chemical or thermal control, improves fish health and welfare, accelerates biomass growth, and increases fish farm productivity and profitability in a R&D point of view, CaliSonic project is within some uncertanity issues due to the transition from pilot to full-scale model, as well there might be challanges to how the ultrasonic system will affect and how it must be arranged for optimal functionality. Anvendelse av prosjektresultat CaliSonic will develop a sea lice control system that supplies oxygenated and clean seawater to sea cages, and eradicates at least 95% of sea lice by physical filtration, ultrasonic cavitation and skirt exclusion. The outcome will be a scalable, flexible prevention system that eliminates the need for chemical or thermal control, improves fish health and welfare, accelerates biomass growth, and increases fish farm productivity and profitability.