The hydrogeochemistry of connected waterways: The potential of linking geology to fish migrations

Many major North American watersheds are connected by canals and diversions, allowing fish migration across watersheds. Unique geochemical "signatures" of watershed waters may be useful as natural tracers if they are incorporated into fish earstones (otoliths). We tested this hypothesis by measuring concentrations of dissolved Ca, Na, Sr, Mn and Ba along the Hudson-Mohawk-Erie Canal system, a trans-basin waterway connecting Lake Ontario to the Atlantic Ocean. The concentrations of these dissolved metals from Adirondack (northern) tributaries were 3-350 times less than in waters from the lower Hudson River, where seawater intrusion occurs, and in the western Mohawk basin, where evaporite minerals dissolve from shales and limestones in the watershed rocks. Of these metals, variation in concentrations of Sr, Mn, and Ba in otoliths from two Alosa aestivalis (blueback herring) corresponded to changes in concentrations the water chemistry where the fish lived as they migrated north from saline waters in the Hudson River estuary and then westward in the Mohawk-Erie Canal drainages. The biochemical response, reflected by otolith metal concentrations corresponding to metal concentrations in surface water along the Mohawk Hudson, forensically can be used to show how both invasive and native fish species take advantage of anthropogenically induced linkages in waterways.