Chum restoration project showing good returns
October 22, 2015
A chum salmon reintroduction project has quietly and successfully moved beyond its fifth year in the Columbia River between Astoria and Clatskanie.
Once one of the most abundant of salmon species in the Columbia River, chum salmon made up as much as 7 percent to 10 percent of historical salmon runs, with as many as 1 million fall-run chum salmon returning to the river in 1928. That was the same year that the commercial harvest of chum was 700,000 fish.
The species went into decline due to harvest and as habitat degraded, and has been in decline since the 1930s and 1940s. It was listed as threatened under the federal Endangered Species Act in 1999.
It’s also one of the most broadly distributed species of salmon in the North Pacific Ocean. It was once found as far south as the Sacramento River and as far north as the Mackenzie River in Alaska, and from Russia south through Korea.
In the Columbia River, chum salmon were found as high up in the river system as Celilo Falls and, according to Kris Homel, the chum salmon reintroduction manager with the Oregon Department of Fish and Wildlife, there are unconfirmed reports of seeing chum in the Walla Walla River.
Homel began her work with ODFW in 2012 and was the first chum reintroduction manager at the state agency. The reintroduction project is funded by NOAA Fisheries’ Pacific Coastal Salmon Recovery Fund.
The year Bonneville Dam was built, 6,000 of the fish climbed the dam’s fish ladder. Even this fall, one chum salmon has found its way over Bonneville despite the fact that 90 percent of the historic chum populations in the Columbia River have been extirpated. Today, Homel said, there are fewer than 10,000 chum salmon adults returning to the Columbia River basin each year.
The decline is due to loss and degradation of spawning habitat, changes in estuary ecology (an area where chum fry spend some extended time), altered river flows caused by dams, predation and harvest.
Today, most chum are found in the lower Columbia River in Washington and Oregon, as well as in some coastal streams in both states.
The chum salmon reintroduction began in 2010 when ODFW, working with the Washington Department of Fish and Wildlife, spawned chum broodstock from the Grays River Hatchery in Washington and transferred the eggs when they were at the eye stage to the Big Creek Hatchery across the Columbia River in Oregon. WDFW began its own chum reintroduction program in 2001.
Chum from Grays River and those from Big Creek (a few natives already were spawning in Big Creek) are genetically identical, Homel said.
The Grays River Hatchery has transferred more than 100,000 eyed eggs each year to the Big Creek Hatchery for rearing and release into the creek. That five year project ended this year.
“Now we are seeing fish come back, enough for the broodstock,” Homel said. “As we get more, we will introduce them into other areas.”
Adult chum have been released upriver from the Big Creek Hatchery since the first adult returns in 2012.
As the number of adult fish returning climbs in numbers, ODFW is expanding the reintroduction of chum to tributaries of the Clatskanie River, she said.
Adults were outplanted to Graham Creek in 2013 and to Stewart Creek in 2013 and 2014. Egg to fry survival in Stewart Creek is about 27 percent. In addition, eyed eggs from broodstock were reared in special containers and released into Perkins Creek in 2014. All are tributaries of the Clatskanie River.
One of the limiting factors for recovery and reintroduction is marine survival, which is 0.22 percent in both Grays River and Big Creek populations. Chum fry are much smaller than other species, leaving their home stream for the lower river estuary when only about 35 millimeters (1.4 inches) to 40 millimeters (1.57 inches), Homel said. They leave the estuary for the ocean when just 60 millimeters (2.36 inches) to 80 millimeters (3.14 inches).
Lower overall abundance, size and the relative lack of turbidity in the estuary (turbidity has declined with the dams, she said) could make them more of a target for predators.
However, in order to make up for the poor marine survival and achieve a stable population, Homel said they need to see freshwater survival as high as 40 percent. “Of course,” she added, “our goal is not just survival, but population growth.”
Straying was initially a concern, she said, with over 60 percent of adult returns going mostly back to Grays River in 2010. However, in 2011 that turned around and the stray rate dropped to just 13 percent.
It was the first brood year, she said, so it’s possible that Big Creek chum simply followed all the other chum to Grays River, or some coded-wire tags could have been lost, affecting the accuracy of the counts.
Regardless, she said, the straying could stretch our understanding of population boundaries for chum. “They may just home in to broad areas where there are no genetic distinctions,” Homel said.
In a presentation at the 145th American Fisheries Society conference in Portland in August, Homel said that among the findings from the five-year program are:
--The conservation broodstock has become self-sustaining and returns are large enough to increase outplanting to other streams.
--The reintroductions have demonstrated that only eyed egg reintroductions have a high enough survival rate to offset low marine survival.
--The quality of spawning habitat, along with marine survival limit chum recovery. Projects, such as the Big Creek reintroduction, must maintain and increase the population artificially with high survival techniques in the short term, research marine survival limitations in the mid-term, and implement watershed-scale habitat restoration in the long term.