The effects of very low doses of the organophosphorous insecticide (malathion) on piscivorous feeding performance in juvenile walleye, Stizostedion vitreum vitreum (Mitchill)

Juvenile walleye (Stizostedion vitreum vitreum, Mitchill) were exposed to short term pulse exposures of malathion in the laboratory. Two experiments were conducted in order to determine the effects of malathion on whole head acetylcholinesterase and piscivory.; Whole head acetylcholinesterase and piscivory was measured in groups of fish exposed to malathion. Although no linear relationship between the acetylcholinesterase activity and malathion was observed, there was a suggestion of hormesis-stimulatory affects at low concentrations. Piscivory was significantly inhibited on four of the five dates. There was no linear relationship between the inhibition of piscivory and acetylcholinesterase.; Juvenile walleye were videotaped in order to quantify actions involved in the process of piscivory. Net foraging efficiency was increased in the exposed walleye but they exhibited alterations in their locomotory and sensory components of piscivory. Activity was increased in malathion exposed walleye including upper water activity and increased prey handling losses. Malathion exposed walleye exhibit increased reactive distances and decreased reactive angles which may limit the amount of prey seen and decrease consumption.; Short term pulse exposure to malathion results in subtle changes in whole head acetylcholinesterase activity in juvenile walleye. Changes in piscivory of associated with but not related to whole head acetylcholinesterase activity. (Abstract shortened by UMI.)...