eel study looks at potential effects of sediment in streams in Siletz Basin
Tribal Aquatics
Program examines eels’
reactions to dirty water
By Diane Rodriquez
A study of whether sediment in
streams affects lamprey eels in the Siletz
River basin is being conducted by the
Tribal Aquatics team.
Several things can affect how much
suspended sediment, also called turbidity,
can affect a stream, things like rotting
leaves, land use practices in the area and
weather events like storms and floods. The
geology and surface soil of the area also
have an effect, said Stan van de Wetering,
Aquatics Program leader and biologist,
who is directing the lamprey eel study.
“There are several dozen different soil
types in the Siletz Basin,” he said, defin-
ing soil as what is in the top three to six
feet of the ground. Geology in the basin
also is diverse.
He described the basin as having
erodible (softer, sand-like and easier to
break apart) and non-erodible (hard or
granitic) rocks.
Soils often are washed into streams
during rain events while rocks (erodible
and non-erodible) often are supplied to
streams during landslides. The soils often
are immediately suspended in the water
column whereas the rocks are worn over
time and ground into smaller particles that
later get suspended during high-flow events.
These eels are in a large container in a
separate part of the fish hatchery.
The Aquatics Program has been
working on measuring turbidity in Siletz
streams for the past 12 years. Its work
has focused on determining what portion
of the suspended sediment is natural and
what portion may be from human-caused
activities. It now is taking that earlier
work and using it to examine whether
increases in turbidity affect lampreys, i.e.,
do they care?
Both studies are funded through a
grant from the Environmental Protection
Agency (EPA) and are part of a larger
effort to examine what we call best man-
agement practices used by the Oregon
departments of Forestry and Agriculture.
The second study is a lab-based one and
the current year is a “pilot” year.
“During the pilot year we’ll work
with the fish to determine if the tank
configuration works properly, we’ll
examine the extent of variation between
fish and we’ll identify how many fish can
be looked at simultaneously,” said van de
Wetering. “If the system works and the
animals respond in any measurable way,
we will carry out a second full study year.”
eels in lab at fish hatchery
Adult eels in fresh water don’t eat
during the winter and instead live off of
stored fats as they burrow under rocks.
In the lab at the Tribe’s Lhuuke Illa-
hee Fish Hatchery for a five-month span
(ending this month), eels have been on the
control side of the experiment or the treat-
ment side. Those on the control side do
not spend any time in dirty water. Those
on the treatment side spend five days
every third week in dirty water. Approxi-
mately 16 eels are in each test group.
In addition to testing the eels’ long-
term response to suspended sediment,
the study examines the eel’s immediate
response to increases in turbidity. One
at a time, eels are placed in clean water
in swim tubes, which initially tends to
increase their anxiety. They remain in the
swim tubes, which are covered to give
them the “burrowing in the rocks” feeling,
for a full day.
Eel heartbeats are represented by gill
beats, which are measured periodically
during this 24-hour period. At some point,
dirty water is introduced into the tube. Gill
beats are measured and the Aquatics team,
which includes Dillon Blacketer and Issac
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Photos by Diane
Rodriquez
The lab at the
Lhuuke Illahee
Fish Hatchery
(above) has
compartments that
hold water with
various levels of
sediment in them.
These two eels
(right) are in a
compartment with
cleaner water.
Kentta, look for differences in the number
of gill beats, which can indicate the level
of stress an eel is experiencing.
The Tribe will examine whether
hypothesized stress, from muddy water,
can have an effect on the eels’ ability to
reproduce. Greater stress could lead to
reduced fat stores (i.e., energy) and in
turn could influence sperm motility and
the ability of eggs to survive. Eels that
are less stressed generally have more fat,
leading to the possibility of better repro-
ductive rates. Conversely, eels that are
more stressed should be skinnier, which
could reduce their ability to reproduce.
Studies of sperm and eggs from the
“control” eels (those continually in clean
water) and the “treatment” eels (those
exposed to dirty water) can indicate how
dirty water, with varying amounts of sedi-
ment or turbidity, does or does not affect
eels. Then by looking at the turbidity moni-
toring data for streams in the Siletz Basin,
scientists can see what locations can poten-
tially be better for eel restoration efforts.
Results from the study, expected in
the late summer of 2014, will be shared
with the EPA, state of Oregon and
other stakeholder partners, said van de
Wetering, including commercial timber
companies, watershed councils and agri-
cultural land owners.
“The results hopefully will inform
us as to what the best habitats are for
adult lamprey and where our current land
management activities are having positive,
negative or no effects on lamprey survival,
specific to suspended sediment,” he said.
“This could lead to an understanding of
what areas should be protected for lamprey.
In addition, our hope is it will inform us
as to what habitats to restore for lamprey.”
A representative
from the Oregon
Coast Aquarium
talks to Jordan
Smith during
Family Night
at Siletz Valley
School on Feb.
5. The event
was sponsored
by the Tribal
CARE Program.
Several Tribal
and community
programs also
participated.
March 2013
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SiletzNews
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