Intercalibration of scientific echosounders (EK60 and EK80) for the multiplatform acoustic assessment of anchoveta in Chile
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Hydroacoustic surveys are key for assessing pelagic species such as the Peruvian anchoveta (Engraulis ringens) in the Humboldt Current System (HCS), one of Chile’s most important fisheries. Oceanographic variability influences environmental conditions and resource distribution, particularly in coastal areas. However, a coverage gap persists in nearshore zones due to operational limitations of the research vessel, which restricts the spatial representativeness of routine hydroacoustic assessments. To address this gap, artisanal purse-seine vessels equipped with EK80 echosounders have been incorporated, allowing operations in areas less accessible to the main research vessel. This study evaluated the comparability and accuracy of acoustic measurements collected with EK80 echosounders on artisanal vessels against those obtained with an EK60 echosounder aboard the research vessel Abate Molina, during hydroacoustic surveys conducted between 2022 and 2024. Generalized Least Squares (GLS) models were applied to analyze backscattered energy (NASC, 38 kHz), and mean density ratios (Rᵢ) were estimated as intercalibration factors to correct for systematic differences. Results revealed a high correspondence between platforms, with adjusted biomass differences below 5.5% and no significant changes in coefficients of variation, confirming the robustness of the procedure. These findings support the complementary use of multi-platform acoustic surveys as a robust approach to enhance spatial representativeness in stock assessments and strengthen the sustainable management of the anchoveta fishery in the HCS.
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