As many as 80 large, broodstock-sized sturgeon were found dead
this week in the Columbia River upstream of Bonneville Dam, triggering a
complete closure of fishing for what some are calling “valuable, almost
Preliminary investigations point to warmer than average
water temperatures as the cause of the die-off, prompting the two-state
Columbia River Compact to close the river to recreational sturgeon fishing
until further notice, effective Saturday, July 18 -- an action that was unanimously supported by biologists and
river guides alike.
At its Thursday call-in meeting, the Compact closed fishing
from Bonneville Dam upstream to the Oregon and Washington border. The
Washington Department of Fish and Wildlife immediately followed with a closure
up through Hanford Reach, including adjacent tributaries.
“What we see in the river is extremely disturbing,” said
WDFW’s Guy Norman. “Especially since it is happening to large, broodstock-sized
sturgeon at a time when they are actively spawning. While there is no evidence
that this is directly related to fishing, it is prudent to minimize the stress
on these fish.”
River conditions are lower, warmer and clearer than recent
five- and ten-year averages, according to Compact staff. Outflow at Bonneville
Dam is 137,000 cubic feet per second, while the five-year average at this time
of year (July 1-14) is 287 kcfs. Water temperature at the dam is 73 degrees
Fahrenheit, while the five-year average is 65 degrees.
The high water temperatures, biologists believe, is the
cause of the sturgeon die-off in the Columbia River, as well as salmon and
steelhead deaths in other Northwest rivers, including confirmed mortalities due
to warm water in the Willamette, Deschutes and John Day rivers.
“What we’re seeing right now is higher levels of summer
mortality and indications that sturgeon are under a lot of stress this summer.
This is something we can do immediately to give them some relief,” said Chris
Kern, deputy administrator of the Oregon Department of Fish and Wildlife fish
division, of the closure.
Robin Ehlke, a member of the Compact staff from WDFW, said
that 67 of the sturgeon were found in the John Day Dam pool, 5 in the
Bonneville pool, 13 in The Dalles pool and 5 in the McNary pool. WDFW had some
information that is not confirmed of dead sturgeon in the Hanford Reach, she
added. “There are at least five and it could be as many as sixteen,” she said.
Biologists have been seeing dead sturgeon for the past one
to two weeks upstream of Bonneville Dam, but the number of dead fish found
significantly increased this week as stream temperatures continue to rise.
“The frequency and magnitude of the reported mortalities in
areas upstream of Bonneville Dam have increased sharply in recent days,” the
Compact staff report says of the sturgeon deaths, as it recommended the sturgeon
Staff is investigating the cause of the sturgeon
mortalities, but say that elevated temperatures and low dissolved oxygen levels
in the water may be significant factors.
Of the 67 dead sturgeon observed in the John Day pool in the
last two weeks, biologists were able to retrieve 29 that were in good enough
condition to study.
“Externally, there were no marks or visible trauma, so they
were in good physical condition,” Ehlke said. “They had full bellies and there
were no hooks in the belly.” Two of the 29 fish had hook marks on the body.
All the sturgeon stomachs were full of sockeye salmon, but
it appears that at least most of the salmon had died prior to ingestion. This,
according to biologists, is common feeding behavior for sturgeon.
Biologists are finding a few dead sockeye in the pool as
well. There is no confirmation that the sockeye had died of columnares, a
bacteria commonly found in fish, but exacerbated by water temperatures that
exceed 60 degrees and that has been found in dead salmon in the Willamette and
However, even if that were the cause of the sockeye deaths,
WDFW pathologists say that it would be highly unlikely the disease could be
transferred to the sturgeon through ingestion.
Although it is rare, this year is not the first time
biologists have seen sturgeon die due to warm water. Ehlke pointed to a smaller
die-off in the John Day pool a couple of years ago and most recently there was
a die-off in the Fraser River in British Columbia.
A more likely cause of the sturgeon die-off is the
decreasing amount of dissolved oxygen as the water warms, according to
information garnered from the Fraser River sturgeon die-off, Ehlke said. The
issue is specific to large sturgeon that typically have a lower metabolic rate
than smaller sturgeon and so are less efficient in getting oxygen from the
It’s uncertain how this die-off will impact the total
abundance of sturgeon in the mid-Columbia River. In the size range of greater
than 55 inches long, according to Ehlke, the abundance in the Bonneville pool
is estimated to be about 3,000 fish. There are 1,300 fish in The Dalles Pool
and approximately 2,800 fish in the John Day pool.
In other action this week, the Compact extended by one day
treaty Indian fishing to 6 pm Thursday, July 16. The treaty fishing this week
began 6 am, Monday, July 13. The change extends fishing to three and one half
days this week. The Compact will meet again Monday to consider more treaty
At the same time, the Compact rescinded planned commercial
gillnetting in the Columbia River downstream of Bonneville Dam. That 12-hour
opening was to have been 7 pm Tuesday, July 14 to 7 am Wednesday, July 15.
Non-treaty commercial gillnetters have taken 99 percent of their allotted fish,
according to Compact staff.
This is despite a higher estimate of the summer chinook run
size to 108,000 fish, up from 100,000 fish estimated by the U.S. v Oregon
Technical Advisory Committee last week. This is the largest run of summer
chinook since 1960. Summer chinook are not listed under the federal Endangered
Species Act and is considered a healthy run of fish. All are destined for
Priest Rapids Dam.
TAC also increased its estimate of the sockeye salmon run to
500,000 fish, up from 480,000 last week.