R8 PM Pesticide Mixtures
Thursday, 17 November 2005: 1:50 PM - 5:30 PM in 331-332

(GRU-1117-923296) Response of pre-spawn coho salmon to pesticides in urban streams in western Washington.

grue, christian¹, Hearsey, James¹, Grassley, James¹, ¹ University of Washington, seattle, WA, USA

ABSTRACT- Recent monitoring suggests that pre-spawn mortality of coho salmon (Onchorynchus kisutch) has increased in natural waters, particularly urban streams in western Washington. Reasons are not known, but it has been suggested that pre-spawn mortality and pesticides in surface waters are linked. In fall 2004, we exposed green male and female coho to a chemical cocktail representative of that reported in urban streams and monitored their time to death, the ability of females to ripen, and effects of the chemical cocktail on brain cholinesterase activity. Treatments consisted of two pairs of fish (2 males + 2 females) given a continuous exposure to the chemical cocktail or clean water. Two 700 gal tanks per treatment were used and new green fish of the appropriate sex were added to the tanks when fish in the tanks died. Nominal concentrations (ppb active ingredient) of 8 herbicides, 2 insecticides and a fungicide were the maximum reported after stormwater events in either spring or fall. With the exception of the fungicide, formulated products (single ai) were used and if possible were selected from those available at retail outlets. Ten or more fish of each sex were exposed to the two treatments over a 6-week period (> 40 total fish). Time to death for each sex was similar between the treatments (mean = ca. 8.3 days); all but 1 treated female and 1 control female ripened, and none of the overt symptoms that have been suggested to be associated with pre-spawn mortality were observed in treated fish. Brain cholinesterase activity was not inhibited in either treated males or females. Results suggest that other factors (general water quality, habitat, or other contaminants) may be responsible for the mortality that has been observed in the field.

Key words: salmon, pesticide mixtures, urban streams, AChE activity