Data from: Historical data to plan the recovery of the European eel

1. Long-term perspectives are critical to understand contemporary ecological systems. However, historical data on the distribution of biodiversity have only rarely been used in applied environmental sciences. 2. Here, we use historical sources to reconstruct the historical range of the European eel, a critically endangered species. We then use this baseline range to set range targets for the recovery of the European eel, as opposed to the abundance-based targets established by the European Union, which are constrained by the poor information on pre-collapse stocks. 3. We collected over 10 000 historical freshwater fish records from Spain in the 19th and 16th centuries, as well as over 25 000 records from the global biodiversity information facility (GBIF) to characterize historical and current European eel distribution in the Iberian Peninsula. We converted fish records into an eel presence–absence data set using subcatchment as spatial unit of analysis and modelled eel distribution in the different historical periods. 4. The eel was historically widespread throughout the Iberian Peninsula, but it has lost over 80% of its original range, mainly due to river fragmentation by dams. Distribution models applied to 16th- and 19th-century data showed a high agreement, supporting the use of the 19th-century estimated distribution as a baseline range. We identified the number and identity of dams that should be made passable for accomplishing specific range recovery targets, for example showing that acting upon 20 dams would make available 60% of the baseline eel range. 5. Synthesis and applications. This work exemplifies how insights gained from historical ecology can support and guide present-day management of migratory fishes. Similar approaches could be developed throughout Europe to plan the recovery of the eel, since there are large amounts of historical eel records. Historical baseline ranges for the eel range should be incorporated into the European Union legal mandates aimed at the recovery of the species.1. 认知当代生态系统离不开长期视角，然而生物多样性分布的历史数据在应用环境科学领域仍鲜少得到应用。 2. 本研究依托历史文献资料，重构了极危物种欧洲鳗鲡 (European eel) 的历史分布范围。随后，我们以此基线分布为参照，为欧洲鳗鲡的种群恢复制定分布范围目标——这与欧盟 (European Union) 基于种群丰度制定的恢复目标截然不同，后者因崩溃前种群数据匮乏而存在局限性。 3. 我们收集了16世纪与19世纪西班牙境内的逾1万条历史淡水鱼类记录，以及来自全球生物多样性信息设施 (Global Biodiversity Information Facility, GBIF) 的2.5万余条记录，以此刻画伊比利亚半岛 (Iberian Peninsula) 欧洲鳗鲡的历史与当前分布格局。我们以子汇水区 (subcatchment) 作为空间分析单元，将鱼类记录转换为鳗鲡出现-缺失数据集，并对不同历史时期的鳗鲡分布开展了建模。 4. 历史上，欧洲鳗鲡曾广泛分布于整个伊比利亚半岛，但如今已丧失超80%的原始分布范围，这主要源于水坝造成的河流阻隔。针对16世纪与19世纪数据构建的分布模型显示出高度一致性，佐证了可将19世纪估算的分布范围作为基线分布。我们明确了为达成特定分布恢复目标所需增设过鱼设施的水坝数量与具体点位，例如研究表明，对20座水坝开展过鱼设施改造，即可恢复相当于基线分布范围60%的鳗鲡栖息空间。 5. 综合与应用 本研究例证了历史生态学所获认知，可为洄游鱼类的当代管理提供支撑与指导。鉴于欧洲境内留存有大量欧洲鳗鲡的历史记录，欧洲全境均可借鉴类似方法规划鳗鲡种群恢复工作。欧洲鳗鲡的历史分布基线范围，应纳入欧盟针对该物种恢复制定的法定强制要求范畴。