Plant-based protein ingredients can successfully replace fish meal in the diet of ballan wrasse (LABRUS BERGYLTA) juveniles

The production of ballan wrasse is hampered by the poor growth and feeding performances and lack of robustness of the species in culture, which is often attributed to sub-optimal nutrition. The commercial marine finfish diets used in ballan wrasse hatcheries, rich in marine ingredients, may not fulfil the species nutritional requirements. This study aimed at evaluating the effects of plant-based ingredients inclusion on the growth, survival, feeding response and digestibility of the species. Simultaneously, the effects of two dietary protein levels were investigated. Ballan wrasse juveniles at approximately 5 g were reared at 15 °C for 70 days. Three Marine Protein:Plant Protein ratios (3.4, 1.6 and 0.9) and two protein contents (51 and 59% CP) were studied, resulting in five experimental diets and one commercial control diet, tested in triplicate. The partial replacement of fish meal by plant-based ingredients was shown to not compromise growth, survival and feed efficiency. Fish fed the Standard CP diets (51% CP) showed a significantly lower FCR (1.2 ± 0.1) compared to fish fed High CP diets (59% CP) (1.4 ± 0.2). Regarding daily feed intake, fish fed the Standard CP diets ate less (1.4 ± 0.2% day−1) than fish fed the High CP diets (1.6 ± 0.1% day−1). Signs of enteritis were observed in two out of three High CP diets. The use of plant-based ingredients, more cost-effective and sustainable than fish meal, has a great potential for the species as they reflect better natural feeding of wild populations thus may promote the hatcheries productivity by reducing feed costs while improving their sustainability index. The study shows that a potential route for optimising diet formulation for ballan wrasse may lie within carbohydrate and lipid contents. Overall, this research contributes to the development of ballan wrasse on-growing feeds to promote the development of ballan wrasse aquaculture and its benefits on sea lice mitigation