J. Exp. Mar. Biol. Ecol. 176 (1994) 27-37 JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY Factors influencing food selection in the abalone zyxwvutsrqponmlkjihgfed Haliotis rubra (Mollusca: Gastropoda) Paul E. McShane”,*, H. K. Gorfine”, I. A. KnuckeyaTb “Marine Science Laboratories, Department qf Conservatim and Environment. Queensclt$ Vietovio, Australirr; “Research Branch. Fisheries Division, Department qf Primary Industry and Fisheries, GPO Box 990, Darwin. NT 0801, Australiu (Received 12 November 1992; revision received 21 September 1993; accepted 11 October 1993) zyxwvutsrqponm Abstract The feeding rates of the abalone Huliotis rubru were measured for a range of macroalgal diets. The macroalgae Gigartina radula, Plocamium mertensii, Ecklonia mdiata, Phyllospora con~osc~, 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. rubru. 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. Key words: Abalone; Haliotis rubra; Macroalgal diet 1. Introduction Studies of the feeding biology of abalone (Hal&is spp.) reveal that Australasian species have a preference for red macroalgae (division Rhodophyta) over brown macro- algae (division Phaeophyta) (Poore, 1972; Shepherd, 1973; Wells & Keesing, 1989); whereas the reverse, in general, is true for abalone from North America (Cox, 1962; Leighton & Boolotian, 1963; Breen, 1980; Tutschulte & Connell, 1988), South Africa (Barkai & Griffiths, 1986) and Japan (Uki et al., 1986). One hypothesis explaining these food preferences in abalone is the presence of unpalatable chemicals which act as chemical deterrents against herbivory (Steinberg 1988, 1989; Shepherd & Steinberg, * Corresponding author. Present address: Ministry of Agriculture, Fisheries, Fisheries Research Division, P. 0. Box 297, Wellington, New Zealand 0022-0981/94/$7.00 0 1994 Elsevier Science B.V. All rights reserved SSDI 0022-098 1(93)E0149-S