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

Abstract

Oceanographic conditions in the Northern Humboldt Current System (NHCS) in 2023 were warm due to the presence of El Niño 2023-2024. The Instituto del Mar del Perú (IMARPE) carried out five marine scientific activities applying hydroacoustic techniques to observe the impact on fishery resources, with the support of fishing industry vessels. This article presents the impact produced on the distributional behaviour 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 reaching up to 66 nm throughout 2023. At the vertical level, it reached up to 190.41 m depth due to the deepening of the oxygen minimum zone 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 hotspots and variable in time due to the characteristics of the NHCS. The anchoveta lengths were consistent in all marine research activities, the growth observed in the summer survey being mirrored in the spring survey, but their body growth was slowed.