Revisiting Asynchrony Between Sardine and Anchovy in Upwelling Ecosystems

Forage fish management is challenged by the apparent sensitivity of forage fish to the environment and by the unpredictable nature of shifts in productivity. One of the best-known relationships between forage fish and their environment is the phenomenon of asynchrony in sardine and anchovy populations, with many documented cases of species replacements and / or asynchronous fluctuations between sardine (Sardinops spp.) and anchovy (Engraulis spp.) Here we evaluate two key components of sardine and anchovy dynamics: degree of asynchrony (covariance in abundance) and replacability (are peak catches or biomass levels similar between species). We assessed asynchrony and replaceability in landings, biomass, and recruitment time series for sardine and anchovy worldwide, and found variations in asynchrony between upwelling ecosystems, as well as differences in replacement between LMEs. We hypothesize that the mechanisms causing asynchronous landings, biomass, and recruitment vary spatially, and that the strength of asynchrony detected is dependent on the length of the observation time series.