Large-Scale Variability of Anchovy Larvae Abundance in the SW South Atlantic Ocean (23º – 40ºS)

Ichthyoplankton abundance and community structure variability have been used to assess the influence of large-scale environmental events (e.g. ENSO) in pelagic ecosystems. Small pelagic fish such as the anchovy Engraulis anchoita is an important component to the pelagic trophic web in the Southwest South Atlantic Ocean (SWAO). We investigate the influence and importance of large-scale environmental forcing on the temporal patterns of larval abundance of E. anchoita. Interannual and seasonal variability in larval abundance was assessed using a data base composed by 22 cruises collected between 1977 and 2010 in the SWAO. Generalized additive models were used to investigate de effect of seasonality (temperature and salinity) and ENSO (Multivariate El Niño-Southern Oscillation Index–MEI). Results showed a seasonal pattern in anchovy larvae abundance with high values in warm months and another peak in late winter/early spring with low mean temperature. Interannual variability was also detected with an inverse relation between mean larvae abundance and MEI. GAM analysis showed non-linear relation between larval abundance and temperature, salinity and MEI. Our findings suggest that anchovy larvae abundance is negatively influenced by ENSO and has two seasonal peaks influenced mainly by temperature.