The Peruvian anchovy (Engraulis ringens) is the most important small pelagic of the Humboldt Current System (HCS), supporting the largest mono-specific fishery in the world. The spatial behavior of this species tends to be very dynamic at different spatial scales, influenced mostly by its biomass level and environmental factors. The aim of this study was to analyze temporal and spatial fluctuations in anchovy spatial distribution off Peru, based and modeled on acoustic data, focusing on large- and meso-scale spatial structures. We employed data from 41 scientific surveys (1994–2016) and Bayesian hierarchical spatial models to obtain the anchovy's spatial distribution, allowing us to identify spatial structures at specific scales. Our results showed similar temporal trends in the number of mesoscale structures, their areas and anchovy density, exhibiting altogether two breakpoints in th...