Fishing historical sources: a snapshot of 19th-century freshwater fauna in Spain

Historical information is needed to describe in a robust manner long-term changes in the distribution of organisms, although it is in general scarce or contained in non-scientific sources. Gazetteers (or geographical dictionaries) constitute a potential source of historical species records, which has not been accurately explored yet. The dictionary edited by Pascual Madoz between 1845 and 1850 extensively described the geography, population and socioeconomic aspects in Spain. The dictionary included abundant information on wild animals and plants, with a special focus on socioeconomically relevant species. Here, we present a database generated by collecting and georeferencing the mentions to freshwater fauna records in the Madoz, which includes 10,750 occurrence records of 39 freshwater-associated taxa from 5,472 localities. This database has been made public and usable (following FAIR criteria) in GBIF. Most of the records correspond to fish (10,201 records, 94.9% of total; 33 taxa), followed by crayfish (418 records, 3.9% of total; one species). Annelids (one taxon), amphibians (one taxon), reptiles (one taxon) and mammals (three species) sum up to 132 records (1.2% of total). The database presented here can be used to estimate the baseline ranges of many freshwater species, which should inform present-day management for the conservation and recovery of endangered species and freshwater communities.