Integrating Gammarus insensibilis in biofloc systems: A sustainable approach to nutrient enrichment and waste valorisation in aquaculture

This research addresses the cultivation of Gammarus insensibilis in biofloc systems. The aim of the work was to valorise and to bioremediate aquaculture effluents while enhancing the nutritional value of bioflocs through the introduction of amphipods, which can be grown in close aquaculture systems. Two experimental diets (aquaculture waste detritus and commercial fish feed) were tested for amphipods in triplicated biofloc systems, against three control tanks without biofloc. The experiment was conducted over a six-week period at a temperature of 20 °C in the absence of light. The water quality, the survival, lipid profile and fatty acid composition of the amphipods and the bioflocs produced were studied. Significant differences were observed in the water quality between the treatment groups and the control, since nitrifying bacteria were present in the bioflocs formed in the treatment tanks. Indeed, 100 % mortality was reached in the control tanks from the second week of the experiment. The fish pellets diet and the pellet-based biofloc resulted in a significantly higher total lipid content than the detritus diet and biofloc. However, no differences were found in the essential long-chain polyunsaturated fatty acids (LC-PUFAs) content (ARA, EPA and DHA) between the commercial pellets and the detritus-based biofloc, thus justifying the enrichment of the biofloc with amphipods. Indeed, the wild amphipods displayed higher levels of saturated fatty acids and omega-6 PUFAs compared to the experimental groups, which demonstrated higher omega-3 PUFAs content, particularly DHA. The study highlights the nutritional advantages of pellet-based diets for amphipods, including improved survival and lipid content, while also emphasising the enhanced nutritional profile of the enriched detritus-based biofloc. We suggest that the integration of aquaculture detritus with supplemental aquafeed in BFT systems will support both the bioflocculation process and the nutritional needs of the amphipods, thereby creating a sustainable and efficient cycle of waste valorisation and live food production. Further research is required in order to study the complete life cycle of amphipods and their reproductive capacity in these systems. A lower water temperature and the inoculation of microalgae should be considered in order to achieve higher survival rates and PUFAs content. • Gammarus insensibilis survived in Biofloc Technology (BFT) systems, feeding on detritus and enhancing biofloc formation. • Bioflocs enriched with amphipods improved their fatty acid profile, especially in essential LC-PUFAs (DHA, EPA, and ARA). • Amphipods and amphipod-enriched bioflocs from BFT are a sustainable, nutritious feed for aquaculture species. • Integrating fish waste with BFT supports bioremediation, reduces environmental impacts, and enhances nutrient recycling.