【Reading】はんようしょく

【English Name】Semi-aquaculture

Han-yoshoku (semi-aquaculture) refers to a production method in which wild juvenile fish or spat are collected and raised by human hands for a certain period before shipping. Unlike full aquaculture (kanzen-yoshoku), which manages the entire process from egg hatching to shipment, it differs greatly in that it depends on the natural world for securing seed stock.

One representative example is the chikuyo (holding culture) of kuruma-ebi (Japanese tiger prawn). In 1905, a method of placing wild juvenile shrimp into seawater ponds to raise them began on Iwa Island in Amakusa, Kumamoto Prefecture, and this area developed into a major center of holding culture. Subsequently, with the progress of research, artificial aquaculture from eggs was also realized, and holding culture continues to be practiced today.

The jimaki (bottom-sowing) of scallops also corresponds to a semi-aquaculture method. Collectors are installed in the sea to gather wild spat, which after about a year of intermediate rearing are released onto the seabed and grown in the natural environment for about 3-4 years before being harvested; this method is widely practiced in Hokkaido and Mutsu Bay in Aomori Prefecture.

Compared with full aquaculture, semi-aquaculture has the advantage of more easily holding down capital investment and feed costs, but it also has the aspect that production volume is difficult to stabilize because the collection of wild seed stock is affected by environmental conditions from year to year. Among the toppings handled at sushi restaurants, there are not a few ingredients derived from such semi-aquaculture.