1979. Occurrence and biology of the trematodes Cotylurus (Ichthyocotylurus) erraticus, C. (I.) variegatus and C. (I.) platycephalus (Digenea: Strigeidae) in the Netherlands. Netherlands Journal of Sea Research 13:61-191. Swenson, W. A. 1977. Food consumption of walleye (Stizostedion vitreum vitreum) in relations to food availability and physical conditions in Lake of the Woods, Minnesota, Shagawa Lake, and western Lake Superior. Journal of the Fisheries Research Board of Canada 34:1643-1654. Szabo, A., J. Nemcsok, P. Kasa, and D. Budai. 1991. Comparative study of acetylcholine synthesis in organs of freshwater teleosts. Fish Physiology and Biochemistry 9:93-99.