Light plays an important role in fish development

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 a ect the function of genes (genetics), growth (physiology), feed conversion and diet (nutrition), stress responses (immunology), and disease development ( sh health) in sh of di erent ages. is suggests that light and its impacts need to be further researched to understand the mechanisms underlying its e ects and to make its use part of contemporary aquaculture. e workshop, which featured six oral presentations, was convened by Christian Philip Unmack (Euro sh) 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 ow, feeding, waste generation) in the sh environment. ese factors have a direct or indirect impact on the stress status of the sh. Di erent lighting technologies can provide solutions to reduce and possibly eliminate this stress.

Jurica Jug-Dujakovi , Steven Van Gorder and Ana Gavrilovi reported on practical experiences with yellow perch, a species that enjoys high market prices for a relatively small (ca 150 g) sh. 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 ow-through system. ey also estimated that the sh would reach market size in 11 months at a constant temperature and light regime. e issue is to grow the sh while slowing the development of the gonads as this can signi cantly a ect the yield. eir experiments revealed that yellow perch has the potential to grow to 150 g in nine months under constant temperature and a constantly extended photoperiod. e sh did not reach sexual maturity in the rst year which improved growth rate and yield. e 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 Di erent 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. e variable was the placement of the light panels: e light source was placed at di erent locations in the sh rearing ponds and the e ects of this variable were investigated through sh survival, swimming ability and cannibalism. e results suggested that submerged light sources may have a positive e ect on larval quality.

A workshop on light and fish at Aquaculture Europe 2023 demonstrated the potential of using light to optimise the conditions under which fish are reared leading to lower levels of stress and better growth rates.

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 e ects of di erent wavelengths of light (red, green, blue, and white) on African cat sh larvae. To do this, they developed a special sh-holding system to detect the data as accurately as possible. ey clearly found that di erent wavelengths of light have di erent e ects on larval survival and growth and that di erent 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 e work presented by Sebastian Marcus Strauch from the Akva

Paci c white shrimp (Litopenaeus vannamei) and the physiological processes involved. e main objective was to identify whether light has any stress reducing e ect during feeding. is was evaluated using computer software that revealed that light intensity had no e ect on the tested parameters.

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 a ect smolti cation, growth, and maturation. By using the right wavelength (colour) and the right quantity (intensity) problems with these physiological processes can be avoided when rearing sh 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 sh is highly topical and that there are many unexplored areas in terms of

AquaFarm 2024, 14-15 February 2024, Pordenone

light and sh behaviour and physiology that need to be investigated and analysed. Research and development colleagues in the eld 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, Urbanyi.Bela@uni-mate.hu