Utilization of different macroalgae by abalone Haliotis discus hannai Ino: Evidence from analyses of fatty acid profiles

The use of different algal species by the abalone Haliotis discus hannai was investigated by using fatty acids (FAs) as trophic markers. Each of six groups of abalones was fed a different diet consisting of powdered algae over an 84-day period. Of the six diets, three consisted of a single algal species, i.e., the brown alga Laminaria japonica (L), the green alga Ulva lactuca (U), and the red alga Gracilaria lemaneiformis (G). The remaining three diets had different 1:1 mixtures of the algal species, i.e., L. japonica and U. lactuca (LU), L. japonica and G. lemaneiformis (LG), and U. lactuca and G. lemaneiformis (UG). The FA profiles of the abalone soft body showed clear changes over the experimental period and differed significantly between the different diet groups. Analyses of variation of specific FAs and multidimensional scaling ordination of overall FA profiles showed that H. discus hannai absorbed L. japonica preferentially over G. lemaneiformis in the dietary group LG and discriminated against U. lactuca in groups LU and UG. Additionally, abalone in group LG had the highest specific growth rate (SGR = 0.73 ± 0.06% d−1), while those in group U had the lowest (0.36 ± 0.07% d−1). Our results for dietary preferences and growth performance suggest that G. lemaneiformis might be used as an alternative to the kelp L. japonica in the diet of farmed H. discus hannai, while U. lactuca may not be suitable.