Inclusion of seaweed meals in abalone (Haliotis tuberculata coccinea, Reeve) diets. Effects on growth performance, body composition and colour

Considering the nutritional variability of wild macroalgae, and the need to limit the use of fish meal in formulated feed for ecological and sustainable abalone aquaculture, a 16 weeks trial was conducted to evaluate the suitability of different seaweed meals, included alone or in combination with fish meal in formulated feeds. Fresh and commercial diets were used as controls. Enriched fresh algae overall demonstrated a significantly higher dietary value for H. tuberculata coccinea than the compound feeds, although not significantly different from the one of UHPaFm, indicating the high dietary value of the IMTA macroalgae. Feeding abalone with fishmeal-free formulated diets resulted in high survival, sustained growth, good protein utilization and natural pigmentation. Nevertheless, the inclusion of P. palmata was found to improve growth, while the use of Porphyra sp. and Gelidium sp. reduced growth, increased FCR and diminished PER. The addition of fish meal significantly improved growth, validating the benefits of combining both vegetal and animal protein sources. The use of commercial abalone diet led to sub-optimal growth, probably linked to a significantly lowest feed intake and due to its non-nutritional properties. The elevated contents of ARA and EPA in abalone tissues denoted the presence of respective elongases Delta4 and delta5 desaturases. Shell and foot colour were altered by the different feeds, indicating that feeding regimes can also be used as tools to mark the specimens or provide colour enhancer to respond to the abalone market demand. Replacing fish meal with Hydropuntia cornea, Ulva sp. and Palmaria palmata meals, was of interest to produce sustainable abalone feed, as they have the potential to provide additional health benefits, and as they can also be cultured under enrichment conditions to enhance their nutritional profile. However, future studies are required to improve the water stability of the formulated diets.