Toxicity of Cedar River Water and Sediment to Larval Walleye

Although all anthropogenic stressors affecting aquatic ecosystems have not been isolated, suspended solids, sediment, and pesticides are believed to be major factors in agroecosystems. In the spring of 1998 and 1999, static 48-h tests were conducted to determine the toxicity of water and sediment collected from the Cedar River to prolarval, postlarval I, and postlarval II walleye (Sttzostedzon vitreum). River water and sediment were not more toxic to any larval stage of walleye than reference water and sediment. Cedar River sediments, suspended solids, and water were examined for occurrence of the most common herbicides and insecticides in Iowa. No pesticides were found in sediments or suspended solids, but metolachlor, desethyl atrazine, acetochlor, and parathion were detected in water samples. However, no adverse effects were observed in larval walleye exposed to Cedar River water containing these pesticides. In addition, cholinesterase (ChE) activity in postlarvae I walleye exposed to Cedar River water containing parathion was not significantly different from postlarvae I exposed to control water. At the time of the study, the results indicated that pesticides were not a threat to survival of larval walleye in the Cedar River