Hiroshima typically accounts for over half of Japan’s total of approximately 200,000 metric tons of fresh oyster meats, but a sharp reduction in the amount of spatted clutch collected there last summer means there won’t be many Hiroshima oysters on the market next year.
Even this year, some oyster farmers are holding back product in anticipation of next year’s shortage, cutting back supplies now.
A single adult oyster can release from 0.5 to 10 million eggs, which soon develop into larvae. In Japanese oyster mariculture, empty oyster or scallop shells contained in wire baskets and suspended from racks are used as a hard substrate or “clutch” to which floating oyster larvae (spat) can attach. Oyster spat, after hardening on the racks for three months, is brought ashore in summer. The shells (spatted clutch) are removed, placed in baskets and washed free of parasites. The shells are then culled into single pieces and examined for predators. Shells with little spat are discarded, while those with spat are attached to ropes and suspended from floats for another one to two years.
Miyagi and Hiroshima prefectures are Japan’s largest producers of spatted clutch, but lower than usual amounts of phytoplankton, on which the oysters feed, in Hiroshima last summer led to less spat being produced. Only 10 to 20 percent of the usual amount of spatted clutch was set out, meaning that from next year production will be sharply curtailed.
Thought the full effects will not be felt until fall of 2015 when that batch starts to reach harvestable size, some oyster farmers are trying to even out the supply and capitalize on the expected higher prices next year by holding over a portion of this year’s small oysters to next year, when they will be larger. As a result, the quantity of oysters delivered to the Tsukiji market is 20 to 30 percent down. Wholesale prices there are JPY 1,500 to 1,800 (USD 12.66 to 15.19, EUR 11.15-13.38) per kilogram, about the same as at the start of the season in October 2014, but higher than at this time last year.
Conversely, Miyagi Prefecture oysters are abundant and flavorful this year, as oyster rafts destroyed by the 2011 tsunami have been replaced and collection of spat there has been successful. This may help to even out supply and stabilize prices.
Fresh oyster meats in Tokyo are selling at retail at around JPY 400 to 500 (USD 3.39 to 4.24, EUR 3.02 to 3.77) per 100 grams, while in Osaka, supermarket sale flyers advertised six water-packed Hiroshima oysters at 498 yen (USD 4.21, EUR 3.70), and 130 grams of Hyogo Prefecture oyster meats at 398 yen, equivalent to 383 yen (USD 3.23, EUR 2.84) per 100 grams.
The reduced volume of Hiroshima oysters is not stopping producers from promoting their product. In the Minato-ward, Tokyo, 5,400 free oyster-based meals such as oyster hotpot and fried oysters will be served on a first-come-first-served basis. However they are also going for joint promotion events with Miyagi oyster farmers. Near Tokyo’s Roppongi station, 2,000 free meals featuring oysters of both areas will be offered, and consumers will get to enjoy the difference in the taste according to the production area.
The three main varieties of the Crassostrea gigas oyster species are the Hokkaido, which is large (up to 40 cm in diameter) and thick shelled with a white mantle; the Miyagi, which is large and flat with a brown mantle and high water content; and the superior tasting Hiroshima oyster, which is small, broad and deeply cupped with a black mantle. The Hiroshima oyster has high levels of glycogen, a sugary starch, and iron.
