 Its range declined as dams were built, flows were diverted, marshes were dredged and drained, and exotic species were introduced to the area.The landscape changed as it was altered for agriculture, livestock were transported in, trees were taken for timber, and riparian vegetation was cleared.Eutrophication occurred in Upper Klamath Lake, a major cause of the decline of this and other local fish, and a major reason why the sucker is not recovering.