Natural stable isotope ratios as a tool in understanding nutrient allocation of protein sources in the growth of farmed abalone, Haliotis midae

Using stable isotope analysis, we assessed the relative contributions of the main protein contributors fishmeal, soya and sunflower meal to mature abalone muscle and gonad tissue over 1 year. Prerequisites for the use of stable isotope mixing models were established in this species. The δ¹³C and δ¹⁵N discrimination factors and turnover rates were influenced by diet composition, and there were tissue-specific and sex-specific differences. Abalone were fed the two combination diets (fishmeal–soya and fishmeal–sunflower meal) grew at similar rates. However, feed was most efficiently utilised in abalone fed a combination of fishmeal and soya. The relative contribution of fishmeal, soya and sunflower meal to female and male abalone tissue growth fluctuated throughout the 1-year study. Overall, fishmeal contributed over 50% of the gonad (54%–82%) and muscle (54%–84%) tissue growth in females. Similarly, fishmeal contributed over 50% of gonad tissue growth of male abalone, ranging from 59% to 87%, while the contribution to meat tissue growth in males ranged from 44% to 94%. These findings support the importance of laboratory studies when using stable isotope analysis and mixing models for nutrient allocation in aquaculture.