Attributes / relations provided by
♦ ¹Lappalainen, A., M. Rask, H. Koponen & S. Vesala, 2001. Relative abundance, diet and growth of perch (Perca fluviatilis) and roach (Rutilus rutilus) at Tvärminne, northern Baltic Sea, in 1975 and 1997: responses to eutrophication? Boreal Env. Res. 6: 107–118
♦ ²del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona.