In the past century, sea lampreys, eel-like creatures that latch on to fish and drain their blood, have devastated lake trout populations. Alewives, a small herring, boomed in population, crowding out other small native fish. Fishery managers introduced …In the past century, sea lampreys, eel-like creatures that latch on to fish and drain their blood, have devastated lake trout populations. Alewives, a small herring, boomed in population, crowding out other small native fish. Fishery managers introduced …