Changes in seashore environments caused by climate variation were closely related to transitions in Boso fishing practices. As ridges formed on seashores due to climate variation, new settlements were established as centers of fishing operations. At the same time, fishermen and innovative fishing technologies were introduced from other regions, in Boso’s case the Tokai and Kinki regions, and new seafood distribution routes were created. Man’s fishing activities have evolved in delicate balance with the natural environment of seas and seashores.