Researchers from IMGGE received funding to conduct a research project through a large infrastructure project, AQUAEXCEL2020, which is funded by the Horizon2020 INFRAIA-1-2014/2015 programme (No. 652831). AQUAEXCEL2020 aims to further support the sustainable growth of the European aquaculture sector. One of its major features is the Transnational Access (TNA) programme, offering external research teams access to 39 unique research infrastructures of the participating partners’ institutes. Interested researchers can propose projects that involve visits of one or in some cases two people to the chosen research infrastructure for periods of up to three months (to read more about the TNA programme, please visit: http://www.aquaexcel2020.eu/transnational-access/tna-overview). Through one such TNA project, researchers from IMGGE, through cooperation with the National Agricultural Research and Innovation Centre, Research Institute for Fisheries and Aquaculture (NAIK, HAKI), Hungary, were involved in the research aimed to improve the production of pike-perch in the recirculation system. Pike-perch (Sander lucioperca) is commercially important fish species with respect to its nutritive value. However, the cultivation of pike-perch in captivity still gives small yields, due to, among other issues, high sensitivity of pike-perch to stress and very poor development of the digestive tract in larval stages. This makes it difficult to make the transition from live food (Artemia) to granulated commercially available food, during the weaning period. This additionally increases the costs of breeding, and also leads to excessive introduction of pathogenic bacteria coming from live food to the closed recirculation system. The consequence of this is poor availability and absorption of nutrients, proteins in the first place, which, along with lipids, represent the main source of nutrients for pike-perch. This results in poor individual growth of fish, high degree of infection and skeletal deformities, as well as significant mortality. Therefore, great efforts are being made to ensure sustainable growth of pike-perch in the recirculation system, which would significantly increase the production in the aquaculture sector, both in Europe and at the global level. One of the biologically acceptable options for promoting the growth of fish in captivity is the use of beneficial bacteria belonging to the genus Lactobacillus, which are often used as probiotics - live organisms that, after being taken in a certain amount, can have a positive effect on the health of the host. Lactobacilli have a long history of safe administration to humans and cattle, with a significant effect primarily in the control of infections and regulation of digestive tract functions. Although the use of lactobacilli in the aquaculture sector has been shown to be effective, there are still no studies on their use in pike-perch culture. Many years of experience of the researchers from the Laboratory for Molecular Microbiology (LMM), IMGGE, in the study of probiotic-host interactions, as well as very rich collection of lactobacilli owned by LMM, opened the door for researchers in IMGGE to take part in the TNA project, which was implemented during 2016. in NAIK- HAKI, through cooperation with IMGGE. NAIK-HAKI is located in Szarvas, Hungary, and is the leading research institute in the field of aquaculture and fisheries in the country. As part of the TNA project, lactobacilli were supplemented to pike-perch larvae grown in recirculation system, either via live food or via dry commercial feed. Treatment with lactobacilli was performed during weaning period, which is the most critical period in pike-perch ontogenetic development. It is expected that lactobacilli would aid nutrient absorption and the control of the level of pathogens in the system. Results of the study showed that application of lactobacilli via live food and/or dry feed, promoted individual growth of fish, improved protein utilization and reduced the frequency of skeletal deformities and the growth of potentially pathogenic bacteria from the genera Aeromonas and Mycobacterium. While further standardization is needed in order to improve the technological and nutritional properties of enriched live food and dry feed, results obtained in this research open a new field in both scientific and commercial applications of lactobacilli as probiotics in pike-perch culture.

The main researcher of above described TNA project was Dr Jovanka Lukic, LMM, IMGGE. The co-researcher was Dr Dejana Kosanovic, Institute of Virology, Vaccines and Sera "Torlak", Serbia. Both, Dr Jovanka Lukic and Dr Dejana Kosanovic had made a research visit to the Indoor System for Fish Disease Challenge (SDC), NAIK-HAKI, where in vivo trial was performed. Experiments in the NAIK-HAKI were performed under the supervision of Dr Galina Jeney, who is the manager of the infrastructure in which the TNA project was realized. Lactobacilli strains used in the study are part of the LMM (IMGGE) collection. After in vivo trial, analyses of fish samples were performed in IMGGE. All experiments performed in the study were financed by an AQUAEXCEL2020 TNA project. In addition to the above-mentioned researchers, other participants of the TNA project were MSc Uros Ljubobratovic, MSc Zsuzsanna Molnar, MSc Geza Peter and Mrs Tijana Ristovic from NAIK-HAKI, as well as Dr Goran Vukotic and Dr Nemanja Stanisavljevic from IMGGE. The research results were published in the international journal Research in Veterinary Science (http://www.sciencedirect.com/science/article/pii/S0034528817300073).

Ljubobratovic U, Kosanovic D, Vukotic G, Molnar Z, Stanisavljevic N, Ristovic T, Peter G, Lukic J, Jeney G. Supplementation of lactobacilli improves growth, regulates microbiota composition and suppresses skeletal anomalies in juvenile pike-perch (Sander lucioperca) reared in recirculating aquaculture system (RAS): A pilot study. Res Vet Sci. 2017 115:451-462. DOI: 10.1016/j.rvsc.2017.07.018

In addition, a popular science audio-visual presentation which describes the results of the research is available at the following link: bit.ly/2jIN4Se.

A feature article of the above described TNA project was published in the AQUAEXCEL2020 newsletter Issue 3 in September 2017 (http://www.aquaexcel2020.eu/sites/default/files/inline-files/AQUAEXCEL2020_newsletter3_web.pdf), which reports main news from the AQUAEXCEL2020 project at regular intervals (to see all newsletters, please visit: http://www.aquaexcel2020.eu/media-centre/media).

Image caption:

Photographs featuring experimental facilities and researchers working on the project. Upper photograph depicts Recirculating Aquaculture System (RAS) in HAKI, where the in vivo trial was carried out, as well as juvenile pike perch on the 26th day posthatching (when the first sampling of fish was performed). Photographs in the middle depict the researchers in fish rearing facilities and laboratories in HAKI during the trial: Tijana Ristovic and Zsuzsanna Molnar (from left to right), Zsuzsanna Molnar, Geza Peter and Uros Ljubobratovic (from left to right).On the lower photographs are Dejana Kosanovic performing experiments in HAKI during the trial, as well as Nemanja Stanisavljevic, Jovanka Lukic and Goran Vukotic (from left to right) in real-time PCR room, in IMGGE, where post-trial analyses were performed.