River ErriffThe River Erriff is a river in Ireland, flowing through County Mayo. A spate river, it is characterised by lively streams and deep fish-holding pools. A waterfall called Aasleagh Falls is near the mouth of the river.CourseThe River Erriff forms from the union of the Owenree and Owenmore Rivers in Glennacally. It flows west-southwest parallel to the N59, passing under Aasleagh Bridge and entering Killary Harbour.WildlifeThe River Erriff is a noted salmon and trout fishery.