GROWTH, INTAKE, FEED CONVERSION EFFICIENCY AND CHEMOSENSORY PREFERENCE OF THE AUSTRALIAN ABALONE, HALIOTIS-RUBRA

Feeding trials were conducted on Haliotis rubra using single-species algal diets. Trials were done over 150-350 days and change in weight was measured at regular intervals. The 6 diets of single species tested were the red algae Jeannerettia lobata and Laurencia botryoides, the green alga Ulva australis, and the brown algae Macrocystis angustifolia, Phyllospora comosa and Ecklonia radiata. The greatest growth rate and feed conversion efficiency (FCE) for a single algal diet was with J. lobata (51.0 mg . day(-1), 4.0% wet weight). The highest intake was of P. comosa (4.1% body weight), but this did not result in a high growth rate (0.8 mg . day(-1)). Neither intake nor FCE were correlated with growth rate, suggesting that these measures are not good indicators of the nutritional value of a food item. The hierarchy of food preference of H. rubra was determined for the 6 test diets of single species based on chemosensory attractiveness, involving direct tactile and gustatory sampling. Abalone exhibited distinct preferences, the most preferred being J. lobata and the least preferred the phenolic-rich E. radiata. The hierarchy of chemosensory preference for the algae tested was related to the growth rate of abalone when feeding on these algae. Thus, preference appears to be under selective pressure to ensure that abalone select foods that are nutritionally valuable, resulting in optimum growth rates. However, the low-phenolic brown algae, M. angustifolia and P. comosa, were less preferred than L. botryoides, despite the negative growth and mortality of animals feeding on this alga.