Forsøksdyr: OPTIMIZE: Light quality and intensity in salmon post-smolts

Godkjenningsdato 06.09.2018

Currently, many commercial RAS operations for smolt production and salmon grow-out are changing their light installation to more energy-efficient LED lights. However, typical white LED light has an incomplete light spectrum compared to daylight, showing a prominent peak in the blue band (~450 nm) and a distinct minimum at ~500 nm between blue and green. To our best knowledge, there is currently no published work available which investigates how the spectral composition of white LED light affects the performance and welfare of salmon post-smolts compared to full spectrum LED light, and there are no universal standards for light intensity during post-smolt production in RAS.

The experiment serves two purposes: (1.) Comparing light quality and intensity for the growth and welfare of salmon post-smolts, and (2.) Testing a machine vision apparatus for determining fish size and estimating biomass in RAS under different light conditions.

Therefore, this experiment is divided into two phases, in which we will first test the effect of different light qualities and intensities on growth, maturation and welfare in salmon post-smolts, and thereafter test the machine vision apparatus with different light qualities to determine precision and accuracy of the device. During this experiment, we will also investigate how water quality in RAS affects the spectral composition and intensity of light throughout the tanks. With increasing feed load, the transmittance of the RAS water will change due to changes in water color and turbidity, ultimately affecting spectral composition and intensity of the light provided from above the tank.

In this study, 7 950 Atlantic salmon post-smolts (Salmo salar) will be used to simulate husbandry conditions typical for commercial RAS operations. The fish will be grown in 12 ppt brackish water from around 90 g to 800-900 g, at maximal densities of 60-75 kg/m3. To investigate the interaction of water quality and light conditions in the tank, the system has to be operated at a constant biomass and feed load towards the end of the experiment.

To produce valid scientific results for improving fish welfare in a commercial production environment, we have to operate at a relevant scale. Our main constraint is to keep a sufficient number of fish to simulate a commercial production environment with a maximal density between 60-75 kg/m3. During the study, the salmon will experience minimal distress since we will be only comparing the effect of light quality and intensity on welfare and growth performance. Maximal fish density will remain below 75 kg/m3, minimal light intensity requirements for salmon will be met in all treatments, and water quality and operational parameters of the system are chosen according to best practice in aquaculture.

The results of this study are relevant to the aquaculture industry, as it focuses on improving fish welfare in salmon post-smolt production and grow-out in RAS. This will be realized by (1.) optimizing light conditions for husbandry, and by (2.) helping to develop a non-invasive tool to estimate biomass in RAS to reduce stress for the fish by reducing the need for handling.