Rishiri Island, a small island off Japan's northernmost point, is well-known "Uni Heaven" with its Rishiri Uni often referred to as "Jewel of the Ocean". During peak season, almost 90% of Gokujo Uni (grade AAA) originate from this area and is one of the most sought-after items by Michelin Star restaurants worldwide.
The island of Hokkaido of course, is where the very best Uni from Japan is harvested. This is because Uni here feed on the Kombu (Kelp), which is a delicacy in its own right, that grows plentifully in the low temperature and nutrient and plankton-rich "Oyashio" water flowing through the island.
By region, the season can be broken down to Hidaka in the Spring, Shiribeshi in the Summer, and Spring/Summer for Northern Hokkaido and winter to spring for Eastern Hokkaido. Rishiri Uni from the northside of Hokkaido is only available early June - September.
Uni Grading System Like any premium product, Uni pricing is based on its grading. This is especially true for Uni headed to the Uni Auction Market, where auctioneers trade hundreds of Uni every morning. Uni auctioneers determine Uni grading by color and texture, and those closer to having a golden color or more discernible bumps on the surface merit more value.