PORTLAND, Ore. — Deformed fish found for years in a stretch of Oregon's Willamette River were damaged by something in the water, not by genetic defects as had been believed, according to a study released Friday.
Scientists, who called their findings "shocking," said they were working to determine the exact cause of the problem and investigating whether there were health risks associated with eating the deformed fish found in a 30-mile section of the river.
"It could be chemical, bacterial, parasites, high river temperature, low oxygen levels, a variety of things," said Steve Ellis, a scientist with EVS Environment Consultants, the Seattle-based firm that conducted the study.
"We need to continue to study this and determine the cause and sources of the problem and then do something about it, which we will do," said Dick Pedersen, manager of the watershed management section of Oregon's Department of Environmental Quality.
The study was conducted near a stretch of the Willamette between Newberg and Oregon City, scientists said. There, 3,500 rainbow trout eggs from a California trout farm were left above a riverbed for two weeks until eyes could be seen. They were then taken to a lab, reared to the fry stage and studied against trout that had been raised in a lab.
Of 372 trout sampled, 34% that had been exposed to Willamette River water for two weeks had deformities, compared with 9% of the fish raised in the laboratory, the study found.
"The types of skeletal deformities we saw are the same type as with other fish" that have come out of the Willamette, Ellis said. In addition, studies have shown that random samples of fish from this part of the river have had deformity rates above 70%, scientists said.
The Willamette winds through the state's most populated areas. "This is a slap upside the head for Oregonians," Ellis said.