The feeding habits of the Ezo abalone, Haliotis discus hannai, changed with growth. Three major changes in the feeding of H. discus hannai were identified by reviewing recent studies on the feeding habits of this species. The first change occurred at the time of the metamorphosis, namely a shift from lecithotrophy to particle feeding. In the second change, when the shell length (SL) reached values of about 0.6?0.8 mm, post-larvae were able to digest diatom diets and they grew more rapidly on efficiently digested strains. The final change consisted of a shift from a biofilm-dominated diet to a macroalgal-dominated diet. Post-larval abalone (> 1.8 mm SL) were able to utilize juvenile macroalgae efficiently. These changes in the feeding habits were closely related to ontogenetic changes in the digestive enzyme activities and the development of the radula morphology.