A poor crop of famed Ariake seaweed, which accounts for roughly 40 percent of the country's seaweed production, has jacked up seaweed bidding prices, according to the National Federation of Fisheries Cooperative Associations.

A worker at a box factory in Kanzaki, Saga Prefecture, looks at cardboard boxes left unused due to the unusually poor seaweed harvest in the Ariake Sea.

The rising prices have become evident amid claims that the Isahaya Bay land reclamation project in Nagasaki Prefecture is responsible for this season's poor seaweed crop in the Ariake Sea. The project is allegedly reducing the volume of fresh seawater from the East China Sea.

The federation said the bid price for a sheet of seaweed measuring 21 by 19 cm has jumped more than 10 percent on average from over a year ago. In some cases, the rise was more than 60 percent.

The findings are based on a survey of prices between Nov. 1 and the end of January at 25 locations nationwide, the federation said, adding that 21 of them saw price increases.

In Wakayama Prefecture, for example, the bid price came to 9.45 yen compared with 5.84 yen a year before, up 61.8 percent, the group said. The national average was 12.87 yen, up 1.40 yen.

A major Nagoya seaweed trader predicted that the price of seaweed used for rice balls sold at convenience stores will not go up in the near future. But he was not sure about prices after summer, when supplies start running low.

Industry officials said seaweed traders and buyers will try to make up for the projected supply decline with seaweed from the Inland Sea area and Aichi and Chiba prefectures.

Nori is a common seasoning in Japanese cuisine and used as a sushi wrapper. Ariake Sea Nori is one of the more well-known varieties.