1National Research Institute of Fisheries Engineering, Fisheries Research Agency, Kamisu, Ibaraki 314-0408, 2Izu Branch, Shizuoka Prefectural Fisheries Experiment Station, Shimoda, Shizuoka 415-0012, Japan
Laboratory experiments were conducted in a recirculating flow tank to evaluate the effects of waves on herbivory by the rabbitfish Siganus fuscescens. Rabbitfish (27 cm FL) increased feeding on the kelp Ecklonia cava or Eisenia bicyclis in a faster oscillating flow with a seasonally increased appetite. When feeding activity was highest, oscillating flow reduced feeding to 50% at the velocity amplitude of 1.1 m/s and to nil at ca 1.5 m/s. Swimming speeds observed in different fish sizes suggested that the upper velocity limit for feeding increased little for larger fish. The results and the wave-induced water velocity predictions indicate that destructive feeding by rabbitfish on kelp is very unlikely to be inhibited by waves on the Pacific coast of central Honshu.