FACTORS INFLUENCING FOOD SELECTION IN THE ABALONE HALIOTIS-RUBRA (MOLLUSCA, GASTROPODA)

The feeding rates of the abalone Haliotis rubra were measured for a range of macroalgal diets. The macroalgae Gigartina radula, Plocamium mertensii, Ecklonia radiata, Phyllospora comosa, Jenerettia lobata, Ulva lactuca and Macrocystis augustofolia showed interspecific variation in ash, nitrogen and energy content; toughness (resistance to penetration); and rates of assimilation and food conversion efficiency by H. rubra. Tests with an artificial diet (agar) showed that feeding rates by H. rubra were influenced by toughness. Toughness also accounted for much of the variation (60%) in the feeding rate on the macroalgal diets. The results of our study show little evidence for chemical deterrence of herbivory for H. rubra, but suggest that food toughness is a primary factor in the feeding preferences of abalone.