PORT ANGELES — State Department of Fish and Wildlife staff took specific precautions to ensure that nearly 1 million baby chinook salmon would survive after they were released into the sediment-plagued Elwha River at the beginning of the month.
There have been no fish deaths observed, an agency official said.
The release that began May 31 was the first since a still-undetermined number of year-old chinook salmon were found dead along the sediment-congested river in the days following an April 5 release of 196,575 smolts from the Fish and Wildlife fish-rearing channel about 3.5 miles from the mouth of the river.
“We are assuming that the sediment contributed to their deaths,” said Neil Turner, hatchery operations manager for the Fish and Wildlife region that includes the Elwha River, adding that stress the fish may have experienced during the release process itself also may have played a factor.
“We see that in yearlings in other places during releases,” Turner said.
The sediment has been unleased in the river, free-flowing for the first time in a century, following the removal of one dam and lowering of another, releasing the mud that once was caught behind the dams.
Turner said that a final count of dead year-old salmon, ranging in length from 4 to 8 inches, from the earlier release was not available.
Rough estimates at the time placed the number of dead fish found in the hundreds, though Fish and Wildlife officials said then that those numbers could not be confirmed.
Turner said staff searched along the river in the days after the dead salmon had been reported and did not find any fish carcasses.
“Once we heard dead fish [were] out there, staff went out to try to find them, and they were gone,” Turner said.
“And that makes us really wonder how many actually died.”
Mike Gross, Fish and Wildlife fish biologist for Clallam County and West Jefferson County, called the April release “a mistake.”
He said at the time that the heavy sediment flowing through the river likely effectively suffocated the year-old salmon by damaging their gills.
Rearing channel staff started releasing 810,000 less-than-1-year-old salmon, or sub-yearlings, at about 8 p.m. May 31 and continued emptying the pool where the fish had been kept the morning of June 1, Turner said.
“There were very few fish present the following morning,” Turner said in a Thursday interview.
“A lot of release strategy is for [the fish] to clear [the pool] in evening hours so the birds don’t get on them.”
Turner said rearing channel staff, keeping the dead salmon found after the April release in mind, took specific precautions for the May 31 release, including exposing 10 sub-yearlings to river water with a turbidity up to roughly 1,800 formazin nephelometric units (FNU), which measure the river’s turbidity, for a week before the release.
None of this group of test fish died during that time, Turner said.
Those 10 sub-yearlings, which ranged from 3 to 4 inches in length, later were dissected by Fish and Wildlife fish pathologists, Turner explained, who found the sediment had little negative effect on the health of the fish.
Rearing channel staff also closely monitored the river itself for dead or dying fish immediately following the May 31/June 1 release.
“[We] had agency employees do some checking at various spots on the river clear down to the mouth and saw no mortality,” Turner said.
“We wanted to cover our bases this time.”
The timing of this release also was done so as to expose the sub-yearlings to the lowest amount of sediment in the river as possible, Turner said, and to avoid the increases in sediment expected this summer following the spring snowmelt in the Olympics.
“We had a window of opportunity, and we went ahead and released them,” Turner said.
The river’s turbidity was hovering around 500 FNUs at the time of the most recent release, according to U.S. Geological Survey data.
“So we felt pretty confident we could release [the sub-yearlings] without ill result,” Turner said.
In the hours following the start of the April 5 release, the river’s turbidity peaked at 1,600 FNUs, according to USGS data.
The sediment coursing down the Elwha has been freed by the removal process for the once-towering Elwha dams, part of a $325 million river restoration project still under way.
Elwha Dam was removed by last March, while removal of the remaining 60 feet of Glines Canyon Dam has been delayed until at least July 1 while private contractors working on behalf of Olympic National Park make corrections to the Elwha Water Treatment Plant.
The corrections are needed because sediment released from dam removal has been unexpectedly infiltrating the Elwha Water Treatment Plant, causing the facility to produce less water for the Port Angeles Water Treatment Plant, and subsequently city residents and businesses, than planned.
The Elwha Water Treatment Plant problems have made the city rely more heavily on its Ranney well, the main source of city drinking water, than anticipated, but city officials have said the well is still providing the city with enough clean drinking water.
Turner said estimating the value of the 810,000 sub-yearlings released is difficult, adding, “They’re invaluable with this dam removal, I’ll tell you that.”
The rearing channel, along with the Lower Elwha Klallam tribe’s fish hatchery, was built along the Elwha River as part of the dam removal and river restoration project to help maintain existing fish stock during dam removal and promote fish population growth as river restoration work continues.
The next scheduled release of young salmon from Fish and Wildlife’s rearing channel is next April, Turner added.
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Reporter Jeremy Schwartz can be reached at 360-452-2345, ext. 5074, or at jschwartz@peninsuladailynews.com.
