Towards sustainable feeds for abalone culture: Evaluating the use of mixed species seaweed meal in formulated feeds for the Japanese abalone, Haliotis discus hannai

• Comparisons were made between five novel diet formulations and fresh L. digitata.
• L. digitata was a more seawater stable feed than the formulated diets.
• Diets containing mixed species seaweed meal were comparable to fish meal diets.
• There were no significant differences in BW/SL ratio and % survival between treatments.

Given the growing importance of the aquaculture sector in contributing to global seafood production, there needs to be a concerted effort to develop commercially relevant and ecologically sustainable feeds for the cultivation of commercially important species. Limitations on the availability and use of fish meal through EU directives (EC Regulation 999/2001 & EC Regulation 183/2005) are focussing research efforts to find alternative sources of protein for aquaculture feeds. Marine algae, although low in protein, are widely being considered as a potential alternative to fish meal as not only do they have the potential to impart additional health benefits when ingested but they can also be cultured under enrichment conditions to enhance their nutritional profile as a feed additive. For abalone (a marine gastropod mollusc), several studies have highlighted the benefits of a diet of fresh mixed species seaweed for cultivation. However, the performance of a mixed species marine algae meal, consisting of Laminaria digitata meal, Palmaria palmata meal and Ulva lactuca meal, in a formulated diet for abalone has not apparently been investigated. In this study, the performance of five novel, isonitrogenous, konjac glucomannan–xanthan gum (KX) bound feeds for the abalone Haliotis discus hannai were evaluated in a 12-week experimental growth trial. Comparisons were made between a basal diet formulation (Diet A), a basal diet + lipids + choline chloride (Diet B) and diets containing mixed seaweed meal (Diet C) or fish meal (Diet D) or mixed seaweed meal + fish meal (Diet E). Freshly harvested L. digitata was included as a natural feed type and experimental control. Dry matter leaching was assessed and no significant differences in the dry matter loss over 3 and 4 days were observed between the experimental KX feeds, although L. digitata was a significantly more seawater stable feed type. Daily food consumption (DFC) of Diet C and Diet E was significantly lower than that of fresh L. digitata and the DFC of Diet D was significantly higher than that of L. digitata. Diet E had significantly higher food conversion efficiency than L. digitata, Diet A, Diet B and Diet D. There was no difference in the protein efficiency ratio (PER) between the formulated diets but the PER of Diet D was significantly different to L. digitata. L. digitata had significantly higher linear growth rates than Diet B, and significant differences in the specific growth rates were observed between Diet A and Diet D only. No significant differences in body weight to shell length ratios and percentage survival between treatments were observed. This study highlights the potential for a mixed species seaweed meal as a fish meal replacement in formulated feeds for abalone.