THE BULLETIN • MONDAY, MAY 24, 2021 A11
Fish
Continued from A1
By late April, more than half the
juvenile salmon captured by the U.S.
Fish and Wildlife Service in that area
tested positive for C. shasta. Genetic
analyses found that, during the first
week of May, 63% of captured fish
contained enough of the parasite’s
DNA to be considered severely sick
— and likely unable to recover from
the disease.
At the end of last week, the Yurok
Fisheries Department collected 106
fish in a screw trap near Weitchpec,
just a few hundred feet upstream
from where the Trinity River joins
the Klamath in its march to the Pa-
cific. Eighty of them were already
dead.
“In a regular trapping season, to
see three to five is normal,” said Ja-
mie Holt, a fisheries technician for
the Yurok Tribe.
On Wednesday morning, Holt
and fellow fisheries technician Gil-
bert Myers launched a boat out to
the screw trap to check on that day’s
catch. The trap looks like a giant ro-
tating cement drum attached to a
barge on the southern bank of the
river. A corkscrew within the drum
funnels fish and other river creatures
into a submerged box at the back
of the barge, powered by the river’s
flow.
They set up buckets and tables
to sort the fish caught in the trap.
By virtue of their size and strength
(or lack thereof), almost all of the
catch are juveniles — some Chi-
nook salmon, steelhead and worm-
like Pacific lamprey. Myers scooped
moss and other debris from the trap,
dumping them onto a slab for Holt
to sort through.
“Oh,” Holt said with glee. “We’re
looking happier.”
It was the most positive catch
since May 4, when fish mortality be-
gan to spike. All in all, 25 fish were
dead, compared to 47 the day prior
and the low 70s before that. Holt
said the “mort bucket,” a recepta-
cle for the dead juveniles, had been
heavily stacked for the past few days.
This was the first day you could see
the bottom.
In the spring and early summer,
the Yurok Fisheries Department
checks the trap every weekday, accu-
mulating data about how C. shasta
is impacting salmon in real time.
The parasite is a natural occur-
rence across watersheds in the Pa-
cific Northwest, but few other rivers
can compare their outbreaks to the
Klamath’s.
“C. shasta’s always present in the
system. It’s just never this prevalent,”
Holt said.
The parasite begins life inside an
annelid worm called Manayunkia
occidentalis, which anchors itself
on rocks and filter-feeds on the riv-
erbed. When the spore matures,
the worm releases it into the water
column where it infects a host fish.
C. shasta then wreaks havoc on the
fish’s insides, causing it to swim er-
ratically and, when the infection is
insurmountable, eventually die. The
spore exits the dead fish and re-en-
ters the worm to restart its life cycle.
The Klamath really stands out
where the worms are concerned, in
what’s known as the infectious zone
downstream of Iron Gate Dam be-
tween the Shasta and Scott Rivers.
Just as it blocks salmon from mov-
ing above it to the Upper Basin, the
dam blocks fine sediment from con-
tinuing downstream.
The dam also heavily regulates
the flow of water in the infectious
zone, creating a relatively calm hab-
itat for the worms. In some areas,
they coat large boulders like a shag
carpet, forming a gauntlet for young
salmon to swim through on their
way to the ocean.
Holt said life for salmon during
their first year at sea is hard enough,
and limiting the number of individ-
uals that even make it to the mouth
of the river only makes things worse.
“This is the time of year that these
guys should not be stressed at all,”
she said. “Their hard time is yet to
come.”
With sediment blocked behind
Iron Gate Dam, the only way to
scour the worms from the riverbed
is through an intense flow event
called a flushing flow, which sends
as much as 6,000 cubic feet per sec-
ond of water from the dam over two
to three days in the spring.
Research has shown that this flow
level is high enough to limit the
worm colonies and mitigate a fu-
ture outbreak. If the dams weren’t in
place, scientists say the natural flow
of sediment combined with storm
events in the winter would likely be
strong enough to check the worms,
and by extension, C. shasta.
“The fix for it in the short term
is water,” said Mike Belchik, senior
water policy analyst for the Yurok
Tribe.
Water is exactly what wasn’t avail-
able this spring, after record-low in-
flows to Upper Klamath Lake and
competing Endangered Species Act
requirements for fish habitat there
The Klamath River at Martins
Ferry, on the Yurok Reservation.
Alex Schwartz/Herald & News photos
Jamie Holt lines up the dead fish collected Wednesday morning by the Yurok Tribe’s Weitchpec screw trap. With 25 “morts,” as
they’re called, it’s the best day fishery staff have seen since the beginning of May. But it’s still well above what they’d expect in a
typical year — and a typical river system.
Wednesday’s trapped dead fish that have succumbed to the disease C. shasta.
Though trap mortality has lowered in the past week, spore counts have jumped up
again, suggesting that the outbreak is not over.
forced the Bureau of Reclamation
to cancel a spring flushing flow for
salmon on the Klamath River.
Coho salmon in the river are al-
ready listed as threatened under
the ESA, and the Karuk Tribe and
Salmon River Restoration Council
recently submitted a petition to the
National Marine Fisheries Service to
list spring Chinook salmon as well.
The petition cited C. shasta as a fac-
tor threatening species survival.
Beyond receiving baseline flows
from Iron Gate Dam as outlined in
the NMFS Biological Opinion con-
cerning Coho salmon, the Klam-
ath’s major tributaries, like the Scott,
Shasta, Salmon and Trinity Rivers,
are also flowing significantly below
normal. The Klamath River at Orle-
ans, which at this time of year would
flow at a median of nearly 10,000
cubic feet per second, is seeing less
than 40% of that normal level.
Given how warm and dry this
spring was, researchers say a can-
celled flushing flow meant a recipe
for disaster on the entire lower river
beyond just the infectious zone.
Fishery biologists from the Karuk
Tribe further upstream have re-
ported similarly high mortality in
traps near Kinsman Creek, and at
one point in mid-April, all six mon-
itoring sites reported spore concen-
trations above 10 spores per liter.
“This kill is basin-wide,” Holt said.
“Typically, when there’s been die-
offs in the past, it’s been extremely
area-specific.”
For Sascha Hallett, associate pro-
fessor in the department of micro-
biology at Oregon State University
and an expert on C. shasta, the riv-
er’s conditions meant that a fish kill
of this severity wasn’t surprising.
High spring temperatures and con-
siderably low precipitation provided
an ideal environment for a water-
borne outbreak.
“It was a warm, dry spring,” she
said. “That’s immediately of con-
cern.”
Hallett said temperature and flow,
the main drivers of an outbreak,
have a complex relationship. Too
low of a temperature and C. shasta
spores won’t even activate (thus
their disappearance during the win-
ter); too high of a temperature, and
they’ll disintegrate.
But salmon also have their own
temperature threshold: Too cold,
and they won’t migrate; too warm,
and they’ll make too many pitstops
in cold-water creeks, putting them
more at risk of catching and suc-
cumbing the disease as they spend
more time in the river, stressed out
by its high temperature.
Low flows make juvenile salmon
move more sluggishly, while high
flows can flush the worms and
swiftly carry the fish out to sea. If
flows are high but not high enough,
the river allow juveniles to come
into contact with more spores.
When flows are too high, fish stay
sheltered in creeks, too timid to en-
ter the rushing mainstem. Higher
flows also tend to reduce water tem-
peratures.
“There’s a certain sweet spot of
diluting the spores, encouraging the
fish to outmigrate and decreasing
the temperatures,” Hallett said. With
so little water available for manage-
ment decisions this year, the disease
played out with no large-scale miti-
gation efforts to achieve that magic
flow number.
Like any disease, C. shasta has a
variety of epidemiological markers
that provide warning signs for what
could come next. First is the spore
density: Hallett said when that num-
ber rises, you can expect to see the
effects on fish within a couple weeks.
That will first show up in the dis-
ease severity data, in the percentage
of captured fish that are exhibiting
mortality-level loads of the parasite.
Then, traps will start to catch more
and more dead fish.
“A high prevalence of infection is
not particularly concerning,” Hal-
lett said. “What is concerning is the
severity of infection and the popula-
tion-level impact.”
Hallett said another rarity is see-
ing dead fish floating in the river
outside the traps, like the Yurok
Fisheries Department have. Juvenile
fish kills are hard to notice if you’re
not looking for them, as the small
fish usually sink into deep pools or
get eaten by predators when they
die.
“if we are actually observing dead
and dying juveniles, that is a con-
cern,” Hallett said. “Normally, dead
wild fish disappear readily from the
system.”
Seeing dead juvenile salmon float-
ing in the river usually means there’s
too many to disappear.
A large group of Klamath Ba-
sin scientists, researchers and wa-
ter managers convene every Fri-
day morning to discuss hydrologic
conditions in the watershed. The
Flow Account Scheduling Technical
Advisory (FASTA) meetings bring
together multiple datasets, from
spore concentrations to flow levels
to anecdotal observations of river
conditions. Hallett said she’s heard
worried testimony from participants
over the past few weeks.
“The words that have been used
for this year are really quite astonish-
ing,” she said. “If you use the word
‘unprecedented’ for the Klamath
River, that’s saying something.”
Closing up the trap Wednesday
morning, Holt was hopeful that
things would continue to improve.
But Friday’s FASTA meeting pre-
sented less-promising data. Though
spore concentrations had reduced
last week — likely due to cooler, wet-
ter weather and a release of colder
water from the depths of Iron Gate
reservoir — they rebounded this
week at nearly all sites.
The number of fish with severe
C. shasta also reduced to 15%, but
Hallett said that with more healthy
juveniles potentially entering the
spore-rich river from its tributaries,
she expects that number, along with
mortality, to increase again. Also
concerning are increased spore con-
centrations of a second genotype
of C. shasta that specifically affects
Coho salmon.
Even on the Yurok Reservation,
where spore concentrations would
usually be low so close to the river’s
mouth, the Tully Creek site reported
13 spores per liter right below the
confluence with the Trinity River.
“Fish coming in from the Trinity
are entering their own hotspot right
now,” Hallett said. “It doesn’t have an
ending yet.”
As a Yurok tribal member herself,
Holt looks at the dead fish she col-
lects every week and sees more than
just a row of limp, milky colored
salmon. She sees the decline in a life
force the Yurok have depended on
since time immemorial.
It’s a cultural impact at its core,
but there are economic ramifica-
tions too: Due to low returns result-
ing from previous disease outbreaks,
the Yurok Tribe cancelled its com-
mercial fishing season for the fifth
time this year, and subsistence fish-
ing is still highly regulated.
“Eighty fish could potentially feed
10 to 12 families,” Holt said. “Those
aren’t just tribal families — there’s
ocean fishermen and sport fisher-
men. We all live downstream.”
And since salmon spend be-
tween two and five years in the
ocean before making their way
back upstream to spawn where they
hatched, Holt said this fish kill will
have far reaching effects. According
to data from the U.S. Fish and Wild-
life Service, the number of salmon
caught at a trap just downstream
of Iron Gate Dam peaked around
the same time as C. shasta spores,
suggesting that the majority of this
year’s outmigrating juveniles haven’t
been able to escape the outbreak.
“We’re going to feel these losses
two years from now when there’s no
returners,” Holt said.
Hallett pointed out that this year-
class of salmon is also expected to
make up the majority of returners
in 2023, when the four dams on the
mid-Klamath River are slated to be
removed, opening up hundreds of
miles of new salmon habitat.
“It’s grim. Anybody who cares
about the river or works on the river
are concerned about the fate of these
fish,” she said. “If dam removal goes
ahead as scheduled, these are the
fish we’ve got a hope on for repopu-
lating the Upper Basin. We’re not off
to a good start.”
For Myers, it’s especially frustrat-
ing to think about how sophisticated
disease monitoring efforts have be-
come, only for the management
decisions they recommend to be
ignored. In addition to calling for
immediate relief to all communities
in the basin impacted by this year’s
severe drought, he said the water-
shed needs to transform the way it
operates.
“We’ve spent decades building
our scientific infrastructure. We’ve
spent decades developing our biol-
ogists, our teams and our program
to be able to predict and prevent
fish kills from happening,” Myers
said. “We predicted this to happen.
The data laid it out, we presented it.
I don’t know what more we’re sup-
posed to do.”