A vertical free fall plankton net with no mouth obstructions

Abstract

A newly developed vertical free fall net uses a weighted ring to propel it downward through the water at a standard speed. It is closed after a preselected time by a strangling rope secured aboard ship. This design eliminates the three‐point bridle and the long wire in front of a vertically hauled net which cause avoidance reactions in active zooplankton. The depth and volume filtered are unaffected by drift. The net does not require an oceanographic winch for its operation, only a warping drum for retrieval after closure, and therefore can also be used on unspecialized vessels. These properties recommend it is a standard survey sampler.