Eggs and larvae of anchoveta Engraulis ringens off northern Chile during the 1997-1998 El Niño event Huevos y larvas de la anchoveta Engraulis ringens en el norte de Chile durante el evento El Niño 1997-1998

The impact of the El Nino event (1997-1998) on the spatial dynamics as well as on the changes in the aggregation patterns of anchoveta eggs and larvae due to the alteration in the thermal anomalies were analyzed. Six bio-oceanographic surveys were carried out in northern Chile from Arica (18°29'S, 70°19'W) to Antofagasta (23°38'S, 70°24'W) over different periods (before and during) of the 1997-1998 El Nino event. Changes in the vertical distribution and aggregation patterns of anchoveta in early life stages were registered as well as an increase in zooplankton biomass with the arrival of El Nino; moreover, the spatial distribution of anchoveta was altered due to the gradually poleward displacement of spawning areas as a result of the arrival of subtropical warm waters from the north. The increase in zooplankton biomass linked to a change in the species composition suggests a negative impact on the anchoveta larval feeding. Our results suggest that abrupt changes in the environment would have immediate consequences on the spatial distribution of anchoveta in early life stages, causing a potential impact on the recruitment of this small pelagic fish in the Humboldt Current System off northern Chile.