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Here we show how routine acoustic data, primarily collected for stock assessment, allows for a 3D vision of the abiotic and biotic components of marine ecosystem and to study their interactions. Data, which can be obtained from any vessel geared with multi-frequency echosounders, provide relevant information to study the impact of physical processes on biogeochemical and ecological processes marine life and extracting valid information about the pelagic habitat and its spatial structure. All these data are to develop actual Ecosystem-based Fisheries Management in the current context of climate change. As an example we propose a synthesis of a scientific program developed in the Humboldt Current system off Peru which is the most productive in terms of fish and encompasses a shallow and intense oxygen minimum zone.

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Tropical marine ecosystems are highly biodiverse and provide resources for small-scale fisheries and tourism. However, precise information on fish spatial distribution is lacking, which limits our ability to reconcile exploitation and conservation. We combined acoustics to video observations to provide a comprehensive description of fish distribution in a typical tropical environment, the Fernando de Noronha Archipelago (FNA) off Northeast Brazil. We identified and classified all acoustic echoes into ten fish assemblage and two triggerfish species. This opened up the possibility to relate the different spatial patterns to a series of environmental factors and the level of protection. We provide the first biomass estimation of the black triggerfish Melichthys niger, a key tropical player. By comparing the effects of euphotic and mesophotic reefs we show that more than the depth, the most important feature is the topography with the shelf-break as the most important hotspot. We also complete the portrait of the island mass effect revealing a clear spatial dissymmetry regarding fish distribution. Indeed, while primary productivity is higher downstream, fish concentrate upstream. The comprehensive fish distribution provided by our approach is directly usable to implement scientific-grounded Marine Spatial Planning.

Pelagic fauna is expected to be impacted under climate change according to ecosystem simulations. However, the direction and magnitude of the impact is still uncertain and still not corroborated by observational-based statistical studies. Here we compile a global underwater sonar database and 20 ocean climate projections to predict the future distribution of sound-scattering fauna around the world's oceans. We show that global pelagic fauna will be seriously compromised by the end of the 21 st century, if we continue under the current greenhouse emission scenario. Low and mid latitudes are expected to lose from 3 to 22% of animal biomass due to the expansion of low-productive systems, while higher latitudes would be populated by present-day temperate fauna, supporting conclusions drawn from ecosystem simulations. We further show that strong-mitigation measures to contain global warming below 2°C would reduce these impacts to less than half.

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Tropical marine ecosystems are highly biodiverse and provide resources for small-scale fisheries and tourism. However, precise information on fish spatial distribution is lacking, which limits our ability to reconcile exploitation and conservation. We combined acoustics to video observations to provide a comprehensive description of fish distribution in a typical tropical environment, the Fernando de Noronha Archipelago (FNA) off Northeast Brazil. We identified and classified all acoustic echoes into ten fish assemblage and two triggerfish species. This opened up the possibility to relate the spatial different spatial patterns to a series of environmental factors and the level of protection. We provide the first biomass estimation of the black triggerfish Melichthys niger, a key tropical player. By comparing the effects of euphotic and mesophotic reefs we show that more than the depth, the most important feature is the topography with the shelf break as the most important hotspot. We also complete the portrait of the island mass effect revealing a clear asymmetry. While primary productivity is higher downstream, fish concentrate upstream. The comprehensive fish distribution provided by our approach is directly usable to implement scientific-grounded Marine Spatial Planning.