Aspects of the biology of the abalone Haliotis midae (Linne, 1758) on the east coast of South Africa.: 1.: Feeding biology

The diet and the feeding habits of adult (80-150 mm shell length) and juvenile (< 30 mm shell length) abalone Haliotis midae were investigated from the subtidal and intertidal regions at Great Fish Point on the Eastern Cape coast of South Africa. Adults feed on a variety of seaweeds by grazing an attached plants and by trapping drift algae under the muscular foot. Juvenile abalone are grazers, feeding primarily on encrusting algae. Within each of the adult and juvenile sub-groupings, no seasonal differences or size-specific dietary patterns were apparent. Based on algal availability and frequency of occurrence in gut samples, adults selected Ralfsia verrucosa, Ulva spp. and five of the red seaweeds, name ly Plocamium corallorhiza, Calliblepharis fimbriata, Spyridia cupressina, Hypnea rosea and Hypnea spicifera. Algae rejected by adults included several coralline species and the spined kelp Eckionia radiata. Of the six algal types consumed by juveniles, only two were selected, i.e. Ralfsia verrucosa and Corallina sp. Adults exhibited a higher degree of selectivity and their diet generally reflected the most abundant available seaweed. Although the three most available algal types were consumed by juveniles, their level of selectivity was lower than for adults, and many of the available seaweeds were rejected.