Characteristics of Annual Bands Formation as Age Marker of the Hatchery-raised and Wild Sea Urchin Strongylocentrotus intermedius in Northern Hokkaido, Japan

Abstract

To discriminate hatchery-raised and reseeded sea urchins Strongylocentyotus intermedius from the wild ones in shallow waters in Wakkanai, northern Hokkaido, the structural characteristics of one year-aged rings in the charred fifth genital plates and the maximum width were examined. The one year-aged rings of reseeded sea urchins with ALC marking fertilized in August were located adjacently to the clear ring in the center of the genital plates and the maximum widths were significantly wider than those of wild ones. The widths of the sea urchins collected in four reseeded sites were discriminated into two normal distributions with the modes of ca. 500μm and 800-900μm, corresponding to wild and reseeded sea urchins, respectively. It is demonstrated that hatchery-raised S. intermedius reseeded at >13 mm test diameter is allowed discrimination from wild ones by the structural characteristics of the one year aged ring and the wide maximum width.