This paper describes the development of hardware and software designed for observing fish behavior under the sea ice near Syowa Station. during the 34th Japanese Antarctic Research Expedition (JARE-34) 1992-1994. The system consists of one master station and eight secondary stations and ultrasonic pingers. Each secondary station is composed of an ultrasonic transducer. https://thecookiecountesses.shop/product-category/bag-topper/