Colour changes of greenlip abalone (Haliotis laevigata Donovan) fed fresh macroalgae and dried algal supplement

•Shell became green in abalone fed Ulva sp. and brown fed Gracilaria cliftonii.•Nutrient enrichment of algae had little impact on abalone colour.•Abalone had yellow shell and yellow foot by feeding dried Spirulina sp. and Ulva sp.•β-carotene was the main pigment in abalone fed fresh macroalgae and dried algae.

Abalone colour is an important market trait in the seafood industry. Two experiments were conducted over 93 days to test the effect of diet on the colour of the foot and shell of 1-year old greenlip abalone Haliotis laevigata. In Experiment 1, a commercial control diet and two species of fresh macroalgae (Gracilaria cliftonii and Ulva sp.) were used and each macroalgae species was either non-enriched or enriched with nutrients in the culture media. The shell of abalone fed the commercial diet and fresh Ulva sp. was green but abalone fed fresh G. cliftonii developed a brown shell. The fresh G. cliftonii increased shell colour purity while fresh Ulva sp. increased shell brightness. Feeding abalone with either fresh Ulva or fresh G. cliftonii produced yellowish foot. Nutrient enrichment of algae did not significantly affect the pigment contents in both macroalgae and abalone, and had minimal impact on the colour of shell and foot. With the exception of zeaxanthin, the pigment contents were significantly lower in fresh G. cliftonii than in fresh Ulva sp. Moreover, β-carotene was the main pigment in abalone fed both species of fresh macroalgae. In Experiment 2, the inclusion of dietary dried algae affected abalone colour. Three diets including a commercial control diet, a diet containing 3% dried Spirulina sp. and a diet containing 10% dried Ulva sp. were used. The shell of abalone fed dried Spirulina sp. was yellow-brown with higher colour purity while the shell remained light green in abalone fed dried Ulva sp. or the commercial control diet. The colour of abalone foot became bright yellow when abalone fed dried Ulva sp. Abalone fed dried algae contained β-carotene as the principal pigment. This study indicates that fresh macroalgae and dried algae supplementation in feed can change the colour of abalone foot and shell. Feed effect on shell colour was far more than on tissue colour. Feeding abalone with fresh G. cliftonii contributes to the formation of brown colour on the shell.Statement of relevanceFeed manipulation can change abalone shell and foot colour.