Many dams on the list impeded fish migration and degraded water quality.

CNN: Study opens floodgates on dam removal

Similarly, the elimination of Sandstone Dam on the Kettle River in Minnesota opened 30 miles for fish migration and revived recreation in the area.

CNN: Study opens floodgates on dam removal

According to experts, the reason behind the eel's decline largely remains a mystery due to the difficulty in tracking the fish during its migration.

BBC: River ladders give eels a leg up

If this traditional migration is hindered it could lead to a serious decline in fish reproduction which will unbalance the delicate food chain on which this ecosystem depends.

CNN: STORY HIGHLIGHTS