BCO-DMO BlogInstrument: MOCNESS1
The Multiple Opening/Closing Net and Environmental Sensing System or MOCNESS is a family of net systems based on the Tucker Trawl principle. The MOCNESS-1 carries nine 1-m2 nets usually of 335 micrometer mesh and is intended for use with the macrozooplankton. All nets are black to reduce contrast with the background. A motor/toggle release assembly is mounted on the top portion of the frame and stainless steel cables with swaged fittings are used to attach the net bar to the toggle release. A stepping motor in a pressure compensated case filled with oil turns the escapement crankshaft of the toggle release which sequentially releases the nets to an open then closed position on command from the surface. -- from the MOCNESS Operations Manual (1999 + 2003).
The 1m2 MOCNESS system carries nine nets and is designed to fish with a 1m2 net mouth area when towed at a 45o angle (Wiebe et al., 1976). A flow meter mounted on the frame, just ahead of the net mouth, allowed calculation of the volume of water sampled (Wiebe et al., 1976). The data-acquisition software used angle information when calculating volume of water filtered. The 1m2 MOCNESS was fitted with 153um mesh nets and included, in addition to the standard conductivity (Sea-Bird SBE 4) and temperature (Sea-Bird SBE 3) sensors, a transmissometer (SeaTech, 25cm beam) and an oxygen probe (Sea-Bird SBE 13). The 1m2 MOCNESS was towed behind the ship at a speed of 1.5 to 2 knots (2.8-3.7 km h-1) through the water. Winch speed generally ranged from 10 to 25 m min-1 during deployment and 5 to 15 m min-1 during recovery. Target sampling depths for this report were 1000-750m, 750-500m, 500-250m, 250-200m, 200-150m, 150-100m, 100-50m, and 50-surface.
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