Project Portugal 2030

Summary

Fish larvae are particularly vulnerable to disease outbreaks, as both the rearing water and live feed can serve as vectors for potentially pathogenic bacteria (15). High mortality rates during the larval phase, coupled with increased susceptibility of juveniles to opportunistic pathogens, are responsible for significant losses of total global aquaculture production value. Due to the high load of organic substances and continuous disturbance of the microbiota from feed addition and rotifer growth, rotifer cultures tend to favour the proliferation of fast-growing opportunistic bacteria (r-strategists). This has been associated with rotifer colonization with Vibrionaceae members, which have previously been linked with elevated larval mortality (16). The disinfection treatments, in turn, only reduce bacterial numbers without mitigating the risk of transferring harmful bacteria to the larvae. Therefore, it is important to develop strategies to enrich beneficial microbes that can be competitive under rotifer culture conditions, potentially benefiting rotifers and subsequently, the fish larvae, which feed on them. Unlike the commonly advocated "beat them" strategy for microbial management in aquaculture practices, this project aims to investigate a holistic "join them" approach (8) to develop an innovative approach to improve larviculture production. We will combine state-of-the-art microbiome analyses, material sciences, ecotoxicological and zootechnical methods to develop and investigate a new technological framework to suppress the development of pathogens, improve larval survival and promote larviculture production. In addition, upon successful completion, the project's outputs will be subject to technological and societal valorisation, including the development of a new patent or divisional patent and technology licensing to companies in the aquaculture sector. This will be pursued post-project completion, ensuring the translation of our research into practical applications that positively impact the aquaculture industry. Specific objectives: - Develop new composite materials and FPMs for controlled release of chemical microbiome modulators in rotifer cultures and fish larvae rearing tanks (Task 1). - Investigate and screen 25 FPMs produced in Task 1 for their effects on B. plicatilis culture growth, reproduction, oxidative stress, and bacterial community composition in batch cultures (Task 2). - Assess all possible pairwise combinations of selected FPMs from Task 2, for identification of synergistic interactions of different meshes on rotifer performance and microbial community composition. In addition, evaluate the FPMs with best performance in combination with commercially available live feed enrichments (Task 3). - Evaluate and screen the top-performing FPM approaches selected in Task 3 under continuous rotifer cultures and acquire mechanistic insights on the effects of FPMs on rotifer health and microbiome composition and putative functions (Task 4). - Identify the optimal application method of the functional meshes for improving sole larvae rearing (Task 5). - Gain deeper insights into the mechanisms of FPM action on microbiome modulation and fish health during sole larvae rearing and evaluate the effects of the FPM treatment on post-larvae phenotypes and larval rearing success (Task 5). - Provide valuable data for future optimization and large-scale implementation of FPM technology in larviculture systems (Tasks 3, 4 and 5).