Seasonal and diurnal feeding patterns were studied on the herbivorous fish Siganus fuscescens, which was reported to be the causative agents of deforestation of kelp beds in southern coasts of Kii Peninsula, Wakayama Prefecture, Japan. Culture experiments revealed that S. fuscescens feeds Ecklonia most vigorously in late September, ranging from 26 to 29℃ in water temperature. The highest averaged feeding rate recorded during the decade was 3.97%. The feeding time of S. fuscescens in a day was found to be 9:00 to 17:00 with a notable peak from 13:00 to 15:00. To find effective methods of protecting kelp in larger scales, auditory stimuli were challenged in tanks and/or cages using iron drums driven with water and wind energies, respectively. Although auditory stimuli were effective to lowering the feeding rate of S. fuscescens, further studies are needed to overwhelm the acclimatization.
