Abstract
In recent years, the monitoring of marine organisms using quantitative echo sounders has been made possible in coastal regions by the downsizing and price reduction of quantitative echo sounders. We introduce recent research on monitoring using quantitative echo sounders in the Seto Inland Sea, Japan. The present review is focused on two marine organisms, moon jelly （Aurelia aurita）in Hoketsu Bay in the Bungo Channel and largehead hairtail（Trichiurus japonicus）around the Hoyo Strait.
