RP8 Ecotoxicology of Agrochemicals and Pharmaceuticals
Thursday, 17 November 2005: 8:00 AM - 6:30 PM in Exhibit Hall

(GRU-1117-929053) Exposure of fishes to carbaryl following applications to control burrowing shrimp in Willapa Bay, Washington.

Monson, Christopher¹, Bush, Kristin¹, Cabarrus, Jennifer¹, grue, christian¹, Grassley, James¹, Curran, Catherine¹, ¹ University of Washington, seattle, WA, USA

ABSTRACT- Efforts to restrict use of carbaryl to control burrowing shrimp in Willapa Bay, Washington have been driven by concerns over potential effects on non-target species. In 2003, we studied the use of treated areas in the Bay by fishes in an effort to quantify their exposure to carbaryl. Use of the water column above oyster beds by fishes was determined on the first daylight high tide at each of three oyster beds (10-25 ac) preceding two carbaryl spray events (2 and 14 July 2003), and during each of the three subsequent daylight high tides (ca. 6, 30, and 54 h after treatment) using a two-boat trawl net. Exposure was assessed by determining the activity of brain actylcholinesterase (AChE) expressed as total activity and, if possible, in the soluble fraction. The only salmonid captured before and after treatment were juvenile Chinook (Oncorhynchus tshawytsha); additional species of fish included Pacific herring (Clupea pallasi) and shiner perch (Cymatogaster aggregata). Pacific herring (>10) were collected at one site before and after Spray Event 1 and three sites in Spray Event 2. Perch (>10) were only collected at two sites before and after the first spray event. Because of differences in life history (site fidelity and food habits), we predicted that exposure to carbaryl would be greater in the perch than in herring or juvenile Chinook. Maximum inhibition in Chinook was ca. 10%, 15% in herring, and 28% in perch. AChE inhibition in perch increased with time and was greatest in the membrane-bound fraction, whereas inhibition in the herring occurred only during the first tide post spray and differential inhibition was not detected. Results suggest maximum levels of inhibition are less than those associated with overt effects and that the biological significance of forms of the enzyme needs to be determined.

Key words: carbaryl, Pacific herring, shiner perch, AChE activity