Colour change of greenlip abalone (Haliotis laevigata Donovan) fed formulated diets containing graded levels of dried macroalgae meal

This study evaluated the effects of supplementing dried macroalgae meal on the shell, foot and lip colour in terms of colour hue, saturation and brightness and pigment concentration in greenlip abalone Haliotis laevigata. Two species of dried macroalgae meal (Ulva sp. and Gracilaria cliftonii) at four levels (0% basal diet, 5%, 10% and 20%) of dietary inclusion were fed to the abalone (2.89 ± 0.01 g; shell length 22.41 ± 0.06 mm) for 92 days. The abalone fed G. cliftonii meal developed brown-red colour on the shell and the increased inclusion of algal meal resulted in darker brown shells, whereas abalone fed Ulva sp. meal or the basal diet exhibited light green shells. Although foot hue and foot brightness were not influenced by the type and level of inclusion of dried algal meal, the foot colour saturation of abalone fed ≥ 10% macroalgal meal was significantly higher than those fed the basal diet. Abalone developed a green lip when fed ≥ 10% of G. cliftonii meal, whereas lip colour did not change when fed Ulva sp. meal inclusion, compared to the basal diet, and exhibited milky lip colour. Although diet pigments varied with the species of macroalgae and inclusion level, β-carotene was the major pigment in the tissue of abalone fed all test diets and its content increased significantly with the inclusion level of macroalgae in the diet. Abalone fed the basal diet had significantly lower tissue β-carotene than those fed the diets with macroalgal inclusion. This study suggests that the inclusion of ≥ 5% G. cliftonii can produce a brown-red shell and the inclusion of ≥ 10% G. cliftonii intensifies the green colour of the lip. The brown-red colour mark on the shell by feeding macroalgal meal may be used as a harmless shell-marking method for ranching, stock enhancement or growth study in the wild. Statement of relevance Feed manipulation can change abalone shell, foot and lip colour.