セクションアウトライン

  • The MTD net, officially called the MTD Horizontal net (Motoda Horizontal Net), is a plankton net developed in 1971 by Dr. MOTODA Shigeru to evaluate the depth distribution (vertical distribution) of plankton. He is the first professor of the Flotation Biology, School of Fisheries Science, Hokkaido University.

    From the beginning of their studies, plankton collectors used “plankton nets”, which resemble insect nets. Early plankton nets collected planktons by attaching an upward-facing plankton net on top of a weight, lowering it to a predetermined depth, and then hoisting it up. However, this method could not reveal the vertical distribution of plankton in the water. Therefore, various types of plankton nets were made in order to clarify the vertical distribution of plankton.

    The MTD net is Japan's leading stratified plankton collection device, and is still commercially available in the 21st century. 1971 was the year when the final form of the MTD net was announced, but the germination of the idea (simultaneous horizontal multilayer towing) can be seen in Dr. Motoda's notes from the 1950s (Fig. 2). The following 20 years can be considered as the years of repeated trial and error and testing in order to realize the idea.

    Dr. Motoda was a pioneer in the field of plankton research in Japan by developing and publishing a variety of other plankton collection and analysis instruments. Many of the plankton collection and analysis instruments that Dr. Motoda published have been commercialized and are commercially available (Fig. 3). Among these, the “Motoda plankton splitter”, which splits immersed plankton samples in half, is now widely used around the world.

    The laboratory of Flotation Biology in the School of Fisheries Science, Hokkaido University, where Dr. Motoda served as the first professor, was the first university laboratory in Japan to be named after “flotation biology”. This tradition has been carried on in the current Marine Biology and Biodiversity (Flotation Biology), Faculty of Fisheries Science, Hokkaido University.