Introduction
Waterborne feeding systems have gained significant attention in land-based aquaculture due to their potential to improve feed distribution flexibility, reducing microplastic emissions and energy consumption. This feeding system involves delivering feed pellets through water instead of traditional feeding methods such as airborne feeding. By replacing the transporting medium with water, the system is gentler on the feeding pipes and reduce the breakage of feed pellets. Less microplastics is released, thus reducing the environmental impact from the facility.
These systems rely on pumps, pipes, and spreaders to distribute feed throughout tanks, allowing for precise control over feeding rates and reducing feed waste. Waterborne feeding systems can be automated, allowing for more consistent feeding and freeing up labor resources. However, waterborne feeding systems require technical expertise and specialized knowledge to operate and maintain, and can be subject to malfunction, potentially affecting fish health and growth.
With capacities of up to 50 kg feed per minute from each line, the opportunity to schedule feed based on peaks and lows in appetite during the day is far greater. This allows the growth potential to increase and feed conversion rate (FCR) to reduce.
Method
At Hofseth Aquas facilities in Tafjord, Norway, we have a permission of raising 2,000 tons in biomass of rainbow trout ranging from 125g to 1000g. The post-smolt facility contains six tanks with a size of 18m x 4,85m (1234m³). Seawater from depths of 55m and 35m is treated with UV-filters which is used both in process and through the feeding-system. Water within tanks is renewed each hour using 80% new treated water, and 20% recirculated water using degassers.
Tests of waterborne feeding systems and adjusting numbers of feeding outlets to the tanks initiated in January and February. Two tanks had four feeding points installed, and two tanks had eight points installed. We observed visually and using submerged cameras how the fish behaved and how feed pellets were distributed from the feeding points.
To measure the effect of the feeding system, growth rate, feed conversion rate and energy consumption is compared to existing data from our facility which uses traditional feeding systems.
Results
One of the challenges with a waterborne feeding system has been its sensitivity to changes in water pressure. Malfunctions such as low water pressure can temporarily stop the system from operating and can result in lost opportunities for feeding and growth.
Distribution of feed through water has also been difficult compared to airborne distribution. The amount of feeding points in tanks had to be high enough to ensure a good distribution of the areal, while maintaining the water pressure for equal amounths of water and feed to reach each point. With fewer points of feeding, fish gathered in high density, creating empty areas in the tank. With more points of feeding, fish was distributed better in the tanks area, but feed pellet distribution was not satisfactory due to unequal water pressure.
A combination of a high amount of feeding points at different debts and reducing the pipe dimension to maintain optimal water pressure will be ready for testing in May, and results and further development will be presented at the conference alongside results of growth rate, FCR and energy consumption.