Diet shifts and food selection of perch Perca fluviatilis and roach Rutilus rutilus in humic lakes of varying water colour - Estlander, S.; Nurminen, L.; Olin, M.; Vinni, M.; Immonen, S.; Rask, M.; Ruuhijärvi, J.; Horppila, J.; Lehtonen, H. (My University, 2010)