International Programs

Organophosphate insecticides may produce sublethal, adverse effects on salmonid growth, reproduction, maturation, swimming, and feeding. Chlorpyrifos, an organophosphate insecticide, was detected by the Oregon Department of Environmental Quality in the Hood River and tributaries during March 1999 at levels exceeding state water quality standards in the range of 0.011-0.482 µg/L. This timing overlaps with the early life stage development of winter steelhead populations listed as threatened on the Endangered Species Act. Hatchery steelhead were exposed in lab experiments to chlorpyrifos levels within the range detected in Hood River. Glutathione e-transferase activity in the liver was measured as a potential biomarker of exposure to complement biomarker measurements of acetylcholinesterase activity in the brain. Glutathione s-transferase was significantly inhibited after 24 hour exposure, and there was no dose-response after 96 hour exposure. Correlating internal exposure to a sublethal effect, and then a sublethal effect to a declining population, will take many years of research. There are many potential causes of the population decline, interacting and accumulating on a temporal scale of over 150 years and a spatial scale from the Hood River to seas fished by Japan, Canada, and the USA. Drawing relational diagrams in conjunction with standard research encourages the search for component interactions, causal flows, patterns, loops, temporal and spatial consequences and leverage points within the whole system affecting the steelhead population decline.