Three hundred species of zooplankton have been identified in the Bay of Biscay, among which 10% are copepods. Diversity and variability of taxa, with time and space at all scales, are remarkable. Biology, ecology and biomass of species belonging to mesozooplankton are best known, whereas studies on micro- and macrozooplankton species are scarce. Field estimates of growth and secondary production, even of the most frequent and abundant species, are also scarce. Mesozooplankton carbon biomass represents 4-20% of total particulate organic carbon (POC) and ranges between 2 and 300 mgC.m^-3. Highest values of zooplankton standing stock are generally found either in spring, summer or autumn, depending on stations located in mixed and frontal waters, or in the vicinity of estuaries. Values for density and biomass of zooplankton are not linearly related in time and vary by 1 to 2 orders of magnitude in relation to hydrological conditions and seasons. Based on literature and chlorophyll regimes, it appears that zooplankton in the Bay of Biscay is generally food limited; so that, zooplankton (i.e. copepods) may not reach optimum growth and production rates, except in specific water conditions enhancing primary production or high standing stock (≥ 2 µg Chlo a. l^-1) of phytoplankton. Growth of anchovy larvae and reproduction of adults are critical phases in the life cycle of anchovy, which both rely on different and specific food categories. Matching between anchovy spawning, nursery sites and areas with high standing stock and productivity of zooplankton have never been evaluated in the Bay of Biscay.