Improved filtration systems for multiple-serial plankton samplers and their deployment

The sampling characteristics of these instruments can be improved to the extent that simple design criteria are satisfied: minimal long axis and mesh pressure, maximal flow through the recorder. Two new systems are described which appear to give improved performance and have been used operationally at sea. One is a small system for use on vessels with restricted deck space, the other a larger system fitted with a new recorder ☐ having a very large filtering area and active backward water transport achieved with an impeller system. It is also suggested that studies of vertical biotic structure are better performed with oblique, rather than vertical, LHPR hauls.