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