Behaviour and size distribution of anchoveta (Engraulis ringens) under El Niño 2023 in the Northern Humboldt Current System

Oceanographic conditions in the northern of the Humboldt Current System (NHCS) in 2023 were warm, due to the presence of El Niño 2023-2024. The Instituto del Mar del Peru (IMARPE) carried out five marine scientific activities applying hydroacoustic to observe the impact on fishery resources, with the support of fishing industry vessels. This article presents the impact generated on the distributional behavior and size structure of the anchoveta, as well as the oceanographic conditions of temperature, salinity, and oxygen. The results showed that anchoveta inertia was clearly elongated showing a very coastal spatial distribution throughout 2023, reaching up to 66 nm. At the vertical level, it reached up to 190.41 m depth due to the deepening of the Minimum Oxygen Zone (MOZ) and the approach to the coast of the warm water masses. Despite these conditions, the anchoveta maintained its usual characteristics of positive spatial autocorrelation due to the continuity along the coast, structured by the high concentration nuclei and variable in time due to the characteristics of the NHCS. The lengths were consistent in all marine research activities, what was observed in the summer survey reflected a growth mirrored in the spring survey; however, their body growth was slowed.