Fish biologists thought this could be a deadly summer for Rogue salmon, but their fears have cooled along with the water.
Brandon Hiatt, a Klamath Falls fishing guide, cleans a spring chinook salmon at TouVelle State Recreation Area in July. [Jamie Lusch / Mail Tribune]
Despite a dozen recent triple-digit days that had the potential to trigger fatal fish diseases, this summer’s Rogue River salmon migration has been pretty smooth, thanks to plenty of stored reservoir water .
Water releases from Lost Creek Lake have boosted Rogue flows enough to allay biologists’ fears that spring chinook salmon on their way up the Rogue would die from warm water-borne diseases.
Favorable fish conditions have sparked the best spring chinook migration at Cole Rivers Hatchery on Trail since 2017.
And that’s despite a dozen days of air temperatures of 100 degrees or higher in Medford, according to the National Weather Service.
“Without the extra (stored) water we ended up getting, we would have had dead fish,” said Pete Samarin, an Oregon Department of Fish and Wildlife biologist who helps develop Rogue Basin water release plans .
“To me, that’s pretty amazing,” Samarin said.
The next big test begins next week when agencies reset water release plans for the next wave of Rogue salmon: fall chinook.
At the behest of ODFW, the US Army Corps of Engineers will begin increasing water releases from Lost Creek Lake by 20% to help fall Rogue chinook hatch as well as spring chinook of the basin
The push releases were scheduled to begin Thursday, but Samarin called off the move.
Cooler air temperatures and evidence from ODFW fishnet surveys in the lower Rogue show that chinook have yet to leave the chilly confines of Rogue Bay, so Samarin will revise the planned releases early of next week
Only a five-day delay in increased flows gives Samarin confidence that the Rogue will again prevent salmon kills.
“We’re not in the business of wasting water,” Samarin said. “We’ll wait until Monday.”
When reservoir levels were dangerously low in March, biologists expected a third to a half of this year’s fall run of wild chinook to die from warm-water diseases.
But the wet spring filled Lost Creek and its sister reservoir, Applegate Lake, and allowed biologists to craft Rogue flow regimes to prevent disease outbreaks, which have not been seen here in more than two decades.
Biologists have linked air temperatures to warming Rogue waters in the Agness area, where spring and fall chinook must navigate the lower Rogue Canyon to reach the cooler reaches of the superior of Rogue.
Hot weather can raise water temperatures enough to cause outbreaks of natural diseases such as columnar, which attacks chinook gills and can suffocate them en masse.
This spring, it looked like the first columnar outbreak since 2001 was imminent.
“We expected dead fish in July and more dead fish next week,” Samarin said.
But a curious thing happened on the way to this summer’s water piety.
Spring rain, and near-record snowfall at Crater Lake, pushed Lost Creek Lake to nearly full and raised runout forecasts well above average, all but ensuring a safer summer on the river for salmon and the people.
The best disease deterrent is to keep summer flows artificially high, which keeps temperatures low. And this year, that took some work.
Since June 25, the National Weather Service in Medford has recorded 12 days of triple-digit weather, including six in a row from July 24-29, meteorologist Marc Spilde said.
The hot streak peaked on July 29 when the thermometer reached 114 degrees in Medford, Spilde said.
While there’s no way to confidently predict temperatures here later this month, it’s likely that Rogue Valley residents, including its wild salmon, have seen the worst of the year.
As the days get shorter and the sun hits the region for fewer minutes each day, “the likelihood of 100 degrees goes down,” Spilde said.
“It’s much, much harder because the days are so much shorter,” Spilde said.
That said, triple digits are not uncommon in late August and even late September, Spilde said.
The Weather Service has recorded very hot days in Medford through Sept. 27, when temperatures reached a high of 102 degrees in 1963 and again in 2003, Weather Service records show.
Mark Freeman covers the environment for the Mail Tribune. Contact him at 541-776-4470 or email him at mfreeman@rosebudmedia.com.
