MOCNESS is the acronym for Multiple Opening/Closing Net and Environmental Sensing System and is a net system for plankton in the ocean. The system is towed behind a research vessel with a speed of 1.5 knots and consists of five to twenty nets with a mesh size from 64 µm to 3 mm and an area of 1 to 10 m2 which are opened and closed computer controlled at desired depth. The net enables biologists to catch zooplankton and nekton in various depth horizons typically anywhere in the upper 500 m of the oceans. All MOCNESS systems are capable of sampling to 6000 meters depth (10,000 psi). The system includes a SeaBird CTD-probe to measure salinity and temperature at sampling depths, as well as optional dissolved oxygen, PAR (photosynthetically available light), transmissometry and fluorescence sensors.