Historical data to recover the distribution of freshwater fishes across 1950s Japan

Freshwater ecosystems face severe anthropogenic threats, making historical data invaluable for damage assessment and conservation planning. We reconstructed spatial distributions of four culturally significant freshwater fish species, eel, ayu, bitterling, and catfish, across 1950s Japan. To obtain 1950s fish occurrence data, elderly citizens contributed childhood recollections through a national survey, while historical land cover maps from 1950 and topographical factors provided habitat information. Species Distribution Models accurately mapped distributions across the nation for all species examined. Occurrence patterns across the four taxa revealed lowland rivers and coastal corridors as bottlenecks that constrain distributions. Land cover composition determines the permeability of the corridors. Urban development consistently degraded habitat suitability, whereas agricultural wetlands enhanced probability at low-to-moderate landscape proportions. Land-cover analysis revealed species-specific preferences: undeveloped areas benefited ayu, agricultural paddies increased bitterling and catfish occurrence, while forests negatively affected catfish population. Projections to 1985 showed declining habitat suitability, particularly in coastal plains where farmland mosaics gave way to urban development. Contemporary occurrence records diverged from predictions based solely on land cover changes, suggesting that river fragmentation and other factors influence connectivity limitations in lowland areas. Our study captures valuable ecological knowledge before Japan's major environmental transformations, providing a quantitative baseline. Reconstructing ecological conditions from before major environmental disruptions establishes baseline species-environment relationships, which subsequently facilitate both the evaluation of anthropogenic effects and the development of evidence-based restoration approaches. • Nationwide SDM mapped 1950s distributions of four key Japanese freshwater fishes. • Elderly testimonies and 1950 maps provided rare pre-industrial occurrence data. • Paddy and urban landscapes drove habitat responses, their impacts diverging by species. • Species-specific satoyama thresholds showed impacts of post-1960s land shifts. • Findings offered quantitative baselines for freshwater fish habitat restoration.