A strange, snakelike creature is showing up more frequently lately at the end of local river anglers’ lines.  While the first reaction to seeing the creature might result in a cringe or cry for help, their predecessors were here long before the modern-day anglers who now fish the river.  The American Eel (Anguilla rostrate) is a natural part of the river ecosystem, and has been impacted by the four hydro-electric dams placed on the Susquehanna River.  American eels are one of the few catadromous species in world, which means that the adults swim out of freshwater tributaries and into the sea to spawn, the opposite of salmon.  The young eels — called glass eels — drift with ocean currents until they find their home tributaries. As they grow, in their next stage they are called elvers, and it is in this stage that they ascend the rivers and tributaries where their parents matured.  The eels grow to maturity — for about 10 to 14 years — in their native rivers, at which point they descend downstream to the ocean to spawn in the Sargasso Sea. The dams hinder both the upstream migration of the elvers and downstream migrations of the adult eels.  The United States Fish and Wildlife Se...