As the world population grows and economies develop, the demand for food is projected to increase. At the same time, however, the planet’s health cannot be compromised in response to this situation. In order to continue supplying mankind with nutritious food, there are high expectations for aquaculture. On the other hand, in Japan, aquaculture is gaining attention as a way to promote regional development where the population has begun to decline and rural depopulation is rising. This article examines this bipolarized situation.

Seashells are natural materials with calcium carbonate as their principal component which do not contain any harmful substances. Under the principle of “making use of seashells for the sea,” we have developed and been spreading technology utilizing seashells. This technology also contributes greatly to sustainable fisheries, aligning with Goal 14 of the SDGs, to “conserve and sustainably use the oceans.” Ocean Construction has started new initiatives accordingly.

I would like to introduce the activities of hemp merchants in the Edo Period who linked the hemp fields of Tochigi Prefecture, located far from the ocean, and the seas off Kujukuri Beach. Hemp merchants sold Tochigi Prefecture’s yashuu-asa (yashuu-hemp) to the fishing boat owners of Kujukuri Beach, who required vast amounts of hemp for fishing nets. On their return trip, the merchants brought back sardines that had been hung and dried in order to use as fertilizer. The shrewd assessment of a situation in which boat owners wished to sell large amounts of dried sardines, and the Kanuma region’s hemp farmers’ need for dried sardines as fertilizer, is believed to have led to production which benefited both groups.