Large numbers of sea urchin tests have been excavated from prehistoric sites in Japan, showing that sea urchins have been consumed as food by people living near the shore since ancient times. Consumption of raw sea urchin roe was restricted to coastal-dwellers; however, after the introduction of refrigerated transportation in the 1950s, raw sea urchins became widely available as sushi or sashimi. The edible portion of the sea urchin is usually restricted to the ovary and testis, which for culinary purposes are loosely termed as roe. For decades, the loss of seaweed beds and the expansion of barren grounds covered with crustose coralline red algae have been a serious problem for coastal fisheries in Japan. The combined hydrographical factors of high water temperature and low nutrients are believed to be a primary cause for the decline in seaweed beds.