Long-term synchronous trends in small pelagic fisheries catches around the world suggest that fish populations are governed by the same global climate forcings. Recent findings regarding the population dynamics of zooplankton during the lunar cycle in sub-tropical waters may shed light on the influence of the lunar cycle on fish spawning and mortality. Here I hypothesize that, in the short-term, observed changes in zooplankton abundance during the lunar cycle promote periods of enhanced feeding by adult fish and lower mortality (and increased growth) in their early planktonic stages. Furthermore, a striking 9-year periodicity in sardine and anchovy mortality was inferred in four major upwelling areas, coinciding with the long-term variability in lunar illumination. It is suggested that both short- and long-term changes in lunar illumination should be considered when modelling the effect of climate on the natural variability of fisheries.