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Willamette Falls as seen from atop a Portland General Electric dam in Oregon City. State fish biologists expect dead salmon to continue washing ashore near the falls as abnormally warm waters continue to take a toll.
(The Oregonian/Ian K. Kullgren)
As hot weather and low streamflows continue to kill fish in the Willamette River watershed, aquatic lives aren't the only ones at risk.
Dogs are also in danger.
They're highly susceptible neorickettsia helminthoeca, a parasite often found in Pacific Northwest fish including salmon, steelhead, sturgeon and trout. Eating infected fish can sicken dogs, and the symptoms can be deadly.
Commonly referred to as salmon poisoning disease, the parasite becomes a major concern for veterinarians every year when large numbers of dead fish wash ashore.
"We see some dogs literally every year for it," said Eric Brown, a veterinarian at Animal Medical Care in Newport.
This year, concerns about salmon poisoning disease are arising earlier. Hundreds of heat-stricken spring Chinook salmon began washing ashore this week on the lower Willamette and its tributaries, months ahead of their typical fall spawning time.
The coldwater fish prefer temperatures in the 50s. In recent days, the lower Willamette has hovered in the low- to mid-70s.
The Oregon Department of Fish and Wildlife has been monitoring a die-off. During a survey Wednesday, a week into the event, agency biologists found a total of 208 dead fish, mostly Chinook.
The majority of the carcasses washed up below Oregon City's Willamette Falls, but bodies were also counted near the mouth of the Clackamas and on the Santiam and McKenzie rivers.
"These conditions could be more widespread than the survey area, so this is not to be construed as a total number of dead fish," Swart said. "It's probably more."
Rick Swart, a biologist with the state fish and wildlife department, said the death toll would rise in the coming days. An ongoing heat wave is forecasted to produce triple-digit temperatures in the Portland area this weekend. Most of last winter's pitifully thin snowpack has melted, eliminating a crucial source of cool relief for overheated fish.
"As long as we're in the 70s, we're in a bad place," Swart said.
Veterinarians advise pet owners to use common sense if they take their dogs to the water while dead fish are nearby.
"Just because there's a high number of fish on the banks doesn't mean you shouldn't take your dog out," Brown said. However, "most dogs are going to show an interest in it, keep an eye on them."
Symptoms of salmon poisoning show up several days after infection. Initial signs include diarrhea, fever and lethargy, Brown said. If left untreated, symptoms can progress to vomiting, lack of appetite, weight loss and dehydration.
If your dog shows signs of infection, take them to the vet. Salmon poisoning disease is diagnosed through a stool sample.
If the parasite is detected early, treatment is as simple as an antibiotic course and a dewormer. However, vet costs can rise if the dog becomes sick enough to require hospitalization.
"I wouldn't make the assumption that you can give them a week and see if they feel better," Brown said.
For fish struggling to survive in warm waters, a cool spell is the only hope for relief -- and it isn't coming anytime soon.
Swart said enough fish returned to the Clackamas hatchery to meet the state's brood stock needs, but agency biologists have been "hand wringing" over the challenge of keeping fish alive long enough to harvest their eggs in the fall.
The river-fed hatchery has no capacity to cool the water when temperatures become dangerous for fish.
"We're kind of at the mercy of the river," Swart said.
-- Kelly House
khouse@oregonian.com
503-221-8178
@Kelly_M_House