Impact of live feed substitution with formulated diets on the development, digestive capacity, biochemical composition, and rearing water quality of lobster (Homarus gammarus, L.) larvae

The obster aquaculture industry, constrained by limited access to viable and cost-effective feed sources, prompted an investigation into the potential of replacing live feeds with formulated diets for Homarus gammarus larval culture, exploring alternative protein ingredients. Four diets were tested on newly-hatched H. gammarus: live Artemia nauplii (ART), an extruded control diet with krill meal and fishmeal as main protein sources (CTRL), and diets with 15% of dietary protein replaced by shrimp waste meal (SWM) or black soldier fly meal (BSF). Results revealed significant diet-induced effects on digestive enzymes in H. gammarus larvae. ART-fed lobsters exhibited increased trypsin and amylase activities but lower lipase activity than those fed extruded diets, suggesting more efficient utilization of protein and carbohydrate in ART-fed larvae, while formulated diets compensated with efficient lipid utilization. BSF and SWM diets increased exo- and endochitinase activities, likely due to chitin presence. Additionally, CTRL and BSF-fed larvae exhibited elevated body glycogen content. ART-fed larvae displayed a significantly higher ratio of low DNA to high DNA bacteria in their rearing water, indicative of lower nutrient loading. Despite these diet-induced impacts, there was no dietary effect on growth and survival during H. gammarus larval development. The study suggests successful formulated feed utilization by homarid larvae, even with alternative ingredients like BSF and SWM, offering a promising solution to reduce reliance on live feeds in lobster aquaculture. Further research is crucial to assess the long-term implications of the observed physiological responses to the different diets in later life stages.