Impact of spring upwelling variability off southern-central Chile on common sardine (Strangomera bentincki) recruitment

Off southern-central Chile, the impact of spring upwelling variability on common sardine (Strangomera bentincki) recruitment was examined by analyzing satellite and coastal station winds, satellite chlorophyll, and common sardine recruitment from a stock assessment model. In austral spring, the intensity of wind-driven upwelling is related to sea surface temperature (SST) from the Niño 3.4 region, being weak during warm periods (El Niño) and strong during cold periods (La Niña). Interannual changes in both spring upwelling intensity and SST from the Niño 3.4 region are related to changes in remotely sensed chlorophyll over the continental shelf. In turn, year-to-year changes in coastal chlorophyll are tightly coupled to common sardine recruitment. We propose that, in the period 1991-2004, interannual changes in the intensity of spring upwelling affected the abundance and availability of planktonic food for common sardine, and consequently determined pre-recruit survival and recruitment strength. However, the importance of density-dependent factors on the reproductive dynamic cannot be neglected, as a negative association exists between spawning biomass and recruitment-per-spawning biomass. Coastal chlorophyll, upwelling intensity, and SST anomalies from the Niño 3.4 region could potentially help to predict common sardine recruitment scenarios under strong spring upwelling and El Niño Southern Oscillation (ENSO)-related anomalies.