Bias towards brown algae in determining diet and food preferences: The South African abalone Haliotis midae

Abstract

Previous studies of gut contents have suggested that Haliotis midae in South Africa feeds selectively on brown algae, and that the feeding preferences of this abalone might differ from other species in favouring tannin-rich foods in accord with an evolutionary hypothesis based on food availability. In the present study, H. midae specimens were starved for one month, then fed a variety of algae and frozen at intervals thereafter, to assess whether gut contents provide a good estimate of diets. Fragments of the brown kelps Ecklonia maxima and Laminaria pallida disappeared more slowly than did green or red algae from the abalone crop, as expected from work on H. rubra in Australia and the fact that the kelps contain high concentrations of phlorotannins. The apparent extent to which H. midae feeds on E. maxima, derived from gut content analysis, is biased. There is thus no good evidence that any abalone, faced with brown algae rich in polyphenolics, have adapted to select these foods.