Data from: Damming, lost connectivity and the historical role of anadromous fish in freshwater ecosystem dynamics

Recent research has demonstrated the important role that high-biomass species play in the transfer of energy and nutrients across habitat boundaries, as well as the ecosystem consequences of their loss. To contrast the historical and current biomass of historically abundant anadromous forage fish, we combined historical records of habitat loss from damming with contemporary freshwater productivity of alewives and diet data of freshwater predator fish. Significant declines in production occurred by 1850 in the northeastern United States, long before any direct abundance data were available, which would have had significant effects on freshwater prey resources for the numerous predators directly affected by the transfer of nutrients across the freshwater–marine nexus. Current freshwater systems operate at approximately 6.7% of historical capacity of anadromous alewife biomass and abundance. This provides an example of habitat-mediated changes in connectivity limiting nutrient flux and energy flow among populations and species that alter ecosystem function at multiple scales.现有研究表明，高生物量物种在跨生境边界的能量与营养盐迁移过程中发挥着核心作用，而该类物种的消亡亦会对生态系统造成深远影响。为对比历史上种群繁盛的溯河洄游饵料鱼类（anadromous forage fish）的历史生物量与当前生物量，本研究将筑坝引发的生境丧失历史记录、当前灰西鲱（alewife）的淡水种群生产力数据，与淡水捕食性鱼类的食性数据进行了整合。早在可获取直接种群丰度数据的1850年之前，美国东北部的灰西鲱种群生产力已出现显著下降；这一变化会对依赖跨淡水-海洋生境营养迁移的众多捕食者的淡水猎物资源造成严重冲击。当前淡水生态系统中，溯河洄游灰西鲱的生物量与种群丰度仅约为历史水平的6.7%。本研究提供了一则典型案例，展示了生境介导的连通性改变如何通过限制种群与物种间的营养盐通量与能量流动，进而在多个尺度上改变生态系统功能。