The effects of ultrasonic waves for survival and settlement of the barnacle, Balanus amphitrite, were investigated under laboratory condition. Among the three frequencies (19.5, 28, and 50kHz) of ultrasonic waves tested, 19.5kHz was found to be the most effective in decreasing the survival rate of the barnacle nauplii. A 50% reduction in cyprid settlement was achieved by a total irradiation of about 140kPa·sec, defined as the product of acoustic pressure (kPa) and irradiation time (sec), whereas some 4, 300kPa·s was necessary to reduce to 50% the survival rate of nauplii or cyprids.

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A seaweed (Chaetomorpha sp.) grew remarkably in Nori (Porphyra spp.) culture ground in Tokoname City, Aichi Prefecture. In this seaweed bed, the number of Amphipoda (Ampithoe lacertosa, A. valida, Pontogeneia rostrata, and Caprella scaura deceros) increased extraordinarily. These animals grazed the young thallus (seeding culture) of laver from mid-October to December 1993.

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