Zooplankton biomass in different size fractions (53–200 μm, 200–500 μm, 500–1000 μm, 1000–2000 μm and >2000 μm) and abundance of major groups of zooplankton > 500 μm during three cruises carried out in the open NW Mediterranean Sea in 2009, covering three contrasting periods of the seasonal productive cycle.