Aquaculture Europe 2023, 18-21 September 2023, Vienna
Eurofish (Denmark) and MATE (Hungary) jointly organised a workshop at Aquaculture Europe 2023. The theme was light and its effects on fish physiology, growth, and nutrition. The effect of light has been of particular interest to aquaculture researchers and developers in recent years as it has been shown to have a significant effect on fish physiology.
The wavelength, duration of illumination, colour, and intensity of light all affect the function of genes (genetics), growth (physiology), feed conversion and diet (nutrition), stress responses (immunology), and disease development (fish health) in fish of different ages. This suggests that light and its impacts need to be further researched to understand the mechanisms underlying its effects and to make its use part of contemporary aquaculture. The workshop, which featured six oral presentations, was convened by Christian Philip Unmack (Eurofish) and co-chaired by Béla Urbányi (MATE).
Mitigating stress in fish with light therapy
Gyles Westcott from Biosystems, a division of a UK company, TMC, showed in his presentation how researchers had studied six parameters (oxygen, temperature, pH, water flow, feeding, waste generation) in the fish environment. These factors have a direct or indirect impact on the stress status of the fish. Different lighting technologies can provide solutions to reduce and possibly eliminate this stress.
Jurica Jug-Dujaković, Steven Van Gorder and Ana Gavrilović reported on practical experiences with yellow perch, a species that enjoys high market prices for a relatively small (ca 150 g) fish. Reaching this size takes two years in pond and cage culture in the North American Great Lakes area. In contrast, they estimated it would take 11-13 months at 20-22 degrees C in a flow-through system. They also estimated that the fish would reach market size in 11 months at a constant temperature and light regime. The issue is to grow the fish while slowing the development of the gonads as this can significantly affect the yield. Their experiments revealed that yellow perch has the potential to grow to 150 g in nine months under constant temperature and a constantly extended photoperiod. The fish did not reach sexual maturity in the first year which improved growth rate and yield.
The author Balázs Kucska from the Hungarian University of Agriculture and Life Sciences, and co-authors Gabriella Stettner, Zoltán Horváth, Tamás Müller, Anna Siklósi, and Uros Ljubobratovic, investigated the larval growth of pike-perch in their presentation “Improving Intensive Larval Rearing of Pike-perch (Sander lucioperca) – Using Different Lighting”. In their experiments they subjected the larvae to 16 h of light with an intensity of 70-450 Lux, and 8 h of dark. The variable was the placement of the light panels: The light source was placed at different locations in the fish rearing ponds and the effects of this variable were investigated through fish survival, swimming ability and cannibalism. The results suggested that submerged light sources may have a positive effect on larval quality.
A potential way to improve larval quality
Kevin Nyabuto from the Hungarian University of Agriculture and Life Sciences and colleagues (József Horváth, Ádám Varga, Janka Páskai, Zita Rácz-Végh, Anita Rácz, Balázs Kovács, Julianna Kobolák, Péter Dániel, Béla Urbányi, Tamás Müller) investigated the effects of different wavelengths of light (red, green, blue, and white) on African catfish larvae. To do this, they developed a special fish-holding system to detect the data as accurately as possible. They clearly found that different wavelengths of light have different effects on larval survival and growth and that different sources of light could potentially enhance larval quality.
Charline Pichon from BCF Life Sciences, a French company specialised in the extraction of amino acids, examined in her presentation the feeding behaviour of the Pacific white shrimp (Litopenaeus vannamei) and the physiological processes involved. The main objective was to identify whether light has any stress reducing effect during feeding. This was evaluated using computer software that revealed that light intensity had no effect on the tested parameters.
The work presented by Sebastian Marcus Strauch from the Akva Group, a supplier of technology for the recirculation aquaculture industry, demonstrated that light can be measured in three dimensions, quality, intensity, and photoperiod and that all three affect smoltification, growth, and maturation. By using the right wavelength (colour) and the right quantity (intensity) problems with these physiological processes can be avoided when rearing fish in recirculation aquaculture systems.
More research could benefit fish and farmers
From these presentations it can be concluded that a better understanding of light on the development of fish is highly topical and that there are many unexplored areas in terms of light and fish behaviour and physiology that need to be investigated and analysed. Research and development colleagues in the field have started to build a network that will form the basis for further collaborations.
Prof. Béla Urbányi,
Department of Aquaculture,
Hungarian University of Agriculture and Life Sciences,