As early as the late 1700s, canals were constructed in Northeastern North America. These canals join adjacent watersheds, allowing organisms to cross natural barriers, such as Niagara Falls. The sea lamprey (Petromyzon marinus) is a predacious, eel-like fish native to the coastal regions of the Atlantic Ocean. They were first discovered in Lake Ontario in 1830, through the Erie canal (opened in 1825) from their native habitat in the Atlantic drainage basin, they entered the rest of the Great Lakes through the Welland Canal, after it was opened in 1921. They contributed greatly to the decline of whitefish and lake trout populations in the Great Lakes.