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.