A preliminary report exonerates pesticides as the probable cause of fish deformities in a section of the Willamette River known as the Newberg Pool. Industrial pollutants have contaminated this pool, downstream from Corvallis, Oregon and long been believed to cause these deformities. Researchers with the Departments of Environmental and Molecular Toxicology, Microbiology and Fisheries and Wildlife have evidence that two species of parasites are associated with the lesions and deformities found in northern pikeminnow and chiselmouth fish from this section of the river. Analyses of water from Newberg Pool and upstream near Corvallis found no difference in levels of pesticides, their byproducts or metals between the two sites, nor were there differences in the amount of pesticide residue found in the ovaries of fish collected in these two sites. The water was tested for PCBs, organophosphates and chlorinated pesticides, such as chlordane, two breakdown products of DDT and endrin. Metal analyses for zinc, cadmium, lead and copper were below detectable limits in the water from both sites.

A large number of lesions on the fish had the parasite Apophallus donicus close by and deformities could be produced under laboratory conditions by adding Newberg Pool water to newly hatched fish. There were other lesions that did not have a parasite present at the time of analysis. The parasite could have died or moved on or a second species of parasite was responsible. The number of deformities in a fish was directly related to the number of parasites in the fish.

Researchers still have many unanswered questions including why the Newberg Pool fish are more susceptible to infection and why the Newberg Pool is a better environment for the parasite.

Source: Curtis, Lawrence Environmental Stresses and Fish Deformities in the Willamette River. Project Status Report, December 2003. Prepared for the Oregon Watershed Enhancement Board in cooperation with Oregon State University - Departments of Environmental and Molecular Toxicology, Microbiology and Fisheries and Wildlife.

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