Pre-image population indices for anchovy and sardine species in the Humboldt Current System off Peru and Chile: Years decaying productivity

Pre-image population analysis (PPA) was applied for acoustic biomass and abundance time series for Peruvian and Chilean anchovy and sardine species. These populations have supported one of the most important global fisheries of small pelagic. Today, the trajectory and consequences of fisheries on these species are well known; however, the outcomes obtained by PPA show that precautionary decisions for improving management could be made before consequences occur. In the case of Peruvian sardine and Chilean anchovy, the two principal population model-indices (equilibrium [x*] and growth rate [r]) started decreasing approximately ten years ago, therefore, we should not wait for a drastic reduction of wild stocks to declare a collapsed fishery. The El Niño Southern Oscillation (ENSO) events seem to promote positive delayed impacts in Peruvian and Chilean anchovies and sardine species, exhibiting chaotic or pre- chaotic dynamics with the highest equilibrium and growth rate magnitudes. The pre-image analysis could be used as a complementary analytic tool to traditional population methods since it permits us to monitor transient changes in population dynamics from a historic perspective, improving management strategies such as setting fishing catch quotas, banns and warning us of chaotic dynamics or severe equilibrium and growth rate depletion.