Efforts to boost Columbia River basin salmon survivals are being undercut by toxic chemicals that impact fish health and disease resistance, according scientists from NOAA Fisheries' Northwest Fisheries Science Center.

During a presentation to the Northwest Power and Conservation Council Tuesday, Lyndal Johnson cited research that indicates chemicals absorbed by chinook in the estuary reduce disease resistance and, ultimately, survival as much as the stresses of passing through the basin's hydrosystem and hosts of predators.

"The problem with the contaminants may be comparable to the problem with dam passage," said Johnson, leader of the Reproductive Toxicology Team in the Ecotoxicology and Environmental Fish Health Program.

Monitoring and reducing toxics levels in-river could well be a useful off-site mitigation tool, reducing mortality and lifting salmon recovery efforts, according to Tracy Collier, director of the Environmental Conservation Division at the science center.

The Council had asked, in a letter to the NWFSC, how much the federal hydro system might be contributing to the toxics problem.

The July 6 letter asked eight questions regarding the latest science on toxics' effects on salmon and steelhead that swim up and down the river. The Council is in the process of amending its Columbia River Fish and Wildlife Program.

The information "will help the Council determine any appropriate amendments to address toxic substances in the fish and wildlife program," according to the letter signed by NPCC Chairman Bill Booth.

"In the end, it's really about the salmon," said Collier.

Collier and Johnson briefed the Council on the results to-date of the center's collaborative surveys of toxic chemical exposures and effects in outmigrating juvenile salmon collected at several sites in the lower Columbia River.

They provided samples of what is a growing body of evidence regarding how toxics exposure affects fish.

"We're pretty sure that contaminants are affecting salmon survival," Collier said. Sublethal effects that lead to indirect or delayed mortality have long been documented, he said.

The contaminants come from such point sources as current and past industrial discharges to the air and water and municipal runoff, and from non-point sources such as runoff from chemically treated fields and roads.

They include as well dioxins, polychlorinated biphenyls (PCBs), heavy metals, and other toxic chemicals spilled and dumped in Portland Harbor on the Willamette River from boat building, steel-milling, and sewer discharges.

"Legacy pollutants" banned in the 1970s such as PCBs and chlorinated pesticides such as dichloro-diphenyl-trichloroethane (DDT) are still causing pollution, leaching out from hotspots. Newer chemicals, including modern pesticides, flame retardants such as polybrominated diphenyl ethers (PBDEs), pharmaceuticals, and personal care products are contaminating the river from runoff and sewers.

"The Columbia is right up there with urbanized sites," Collier said. Monitoring has shown that the lower river, below its confluence with the Willamette at Portland, flows with levels of PCBs, DDT and PBDEs that are equal to or higher than levels tested in Puget Sound.

He said the federal Columbia/Snake hydro system does not contribute greatly to the problem, though a dumping ground at Bradford Island at Bonneville Dam has been a PCB hot spot. A cleanup there is in its final stages.

Collier offered a "wild," though educated, guess that the dams contributed "less than 5 percent of the loadings."

But regardless of the source, fish are exposed to a variety of chemicals. Knowledge is growing about the effect of each on fish.

Researchers also "have to consider the effects of multiple" chemicals that might be absorbed in river reaches, Collier said.

A study in Puget Sound has shown high pre-spawn mortality in coho salmon that is linked to stormwater.

"This is a prevelant phenomenon for fish entering urban streams," he said. Studies have shown that greater than 80 percent of urban streams contain three or more pesticides. More than 90 percent of urban, agricultural, and mixed-use streams contain two or more pesticides.

Pesticides too can have lethal effects, and developmental defects causing egg and larval mortality are now known to be linked to stormwater and PAHs.

Sublethal effects from contaminant exposure are numerous. The salmon's sense of smell – essential to avoid predators – and overall behavior can be affected.

Dissolved copper, as an example, that washes from highways can disrupt the salmon's sensory system, which in turn changes their swimming and feeding behavior. Affected fish are slowed so they can't feed or dodge predators as well. That slows their growth and lowers their chance of survival into the next phase of their life.

Chemicals can also reduce disease resistance and the fishes' lipid (fat) content. Once study suggested potential mortality of about 13 percent for fish with less than 1 percent lipid content, Johnson said.

Such loss may, effectively, may undermine the effectiveness of physical habitat restoration efforts in the basin she said.

For more information about the Northwest Fisheries Science Center go to http://www.nwfsc.noaa.gov/index.cfm