The biogeographic ignorance in the distribution of South American goliath catfish

Abstract Biodiversity conservation is challenged not only by the lack of knowledge about species distributions but also by an often-overlooked factor: the unquantifiable uncertainty in the quality and reliability of the data used for decision-making. This challenge is intensified for migratory and overexploited species, such as the goliath catfish Brachyplatystoma filamentosum (‘piraíba’), where management decisions based on data of uncertain reliability can lead to management failures and intensify population declines. Thus, our goal here was to generate Maps of Biogeographic Ignorance (MoBIs) for B. filamentosum based on inventory completeness, taxonomic quality, temporal data decay, and environmental-spatial distance to sub-basins with information, in order to quantify the uncertainty associated with species occurrence data. The MoBIs revealed high spatial heterogeneity in species knowledge. The most comprehensive and recent inventories were concentrated along the main channels of the major river of the Amazon basin, in contrast to the high level of ignorance found in Orinoco, and North Atlantic basins. We also combined these MoBIs with environmental suitability predictions derived from species distribution models. The bivariate maps allowed us to identify sub-basins where high predicted suitability coincides with low ignorance (such as along the main Amazon River), as well as those with high suitability but high ignorance (such as in the western Amazon, the upper Orinoco, and the North Atlantic regions). By quantifying and spatially mapping the quality of occurrence data, our study provides an basis for optimizing research, conservation, and management strategies for this goliath catfish. Graphical Abstract