Sandy River Chinook Salmon
Sandy River Chinook Salmon may be the basis of an important food chain
ROLE OF CHINOOK SALMON
THE SANDY RIVER BASIN
possibly the world?)
by: Mark Bachmann
There are many indications that in the
past, the Sandy River hosted huge runs of Chinook salmon. Of the five
species of Pacific Salmon, Chinooks are the best equipped to exploit
highly fluctual, glacial/volcanic watersheds like the Sandy River basin.
salmon populations have to be pivotal to the over-all fishery management
scheme in this river system. Spring Chinook are the largest spawning
biomass in the upper basin. Fall Chinook are the largest spawning
biomass in the lower main stem. Therefore they are potentially the basis
of the food chain for both trout and steelhead.
spawn and carcasses provide nutrients to the system, both directly and
indirectly. Chinook eggs are ravenously consumed by all sizes of
salmonids, cotids and minnows--- whenever they are available. Salmon
carcasses are prey to all kinds of beneficial insects and plants, which
are also consumed by other species of fish, of many sizes.
fry are some of the earliest to emerge from the gravel. This emergence
provides an early spring meal for trout and steelhead juveniles, which
are two or more years older. Chinook fry are consumed by all fish that
are large enough to eat them.
Peterson who was a fishery tech for the Mt. Hood National Forest was in charge of the Still Creek fish trap. This trap is placed to
capture down stream migrating fish. Most of the fish that have been
caught in this trap are juvenile salmon, trout and steelhead. A small
sample of each specie was killed for scientific study. These studies
included stomach autopsies. John reported that most of the wild steelhead smolts
were gorged on Chinook fry. No doubt resident cutthroat and
rainbow trout partake of this same feast.
Chinook fry emerge January through March. Fall Chinook fry emerge
February through April. They are about 1 1/2 inches long when they
become free swimming. Many Chinook salmon rear in the stream for less
than one year before going to sea. Some start to out-migrate immediately
upon emerging from the gravel. Most are about 1 3/4 to 2 1/4 inches long
when they enter the salt. By comparison, the average out-migrating
steelhead smelts are usually 5" to 7" and may be over ten
inches. Chinook fry emergence is perfectly coordinated with the peak
down stream migration of juvenile steelhead. Juvenile steelhead consume
large amounts of Chinook fry on their way to the ocean. Chinook fry are
large food which permit the steelhead juveniles to grow very quickly and
enables them to compete better in the ocean. Since the Chinook and larger steelhead
are outmigrating together, this symbiotic relationship may continue for
a while at sea. However, ocean rearing Chinooks tend to feed at much
greater depth than steelhead and the two populations are soon parted.
Chinooks out-migrate at a comparative small size, they probably don't
compete much with other species for food or space while in the stream.
They are a wind fall profit in the food chain department. Basin
populations of every other wild salmonid specie are probably highly
dependent on very large healthy populations of spawning and emerging
Chinooks. If we have more Chinooks we will probably have more of
were the most abundant salmonid in the Columbia River basin. They were
also the most desirable salmonid for table fare. They were highly
exploited by indigenous populations of humans for thousands of years.
They were soon over exploited by the present civilization to the point
of near extinction.
…Spring Chinooks are prized as both food
and sport fish…
happened very early in our history. Records show that in 1877 there were
over a thousand 1200' long gill nets and many fish traps working the
Columbia River. All of the larger tributaries also had nets and traps.
Most of the Chinook runs were on the brink by 1885. This is long before
we kept records of wild fish populations. I think that all of the west
slope rivers were much richer in all of their fish runs before the
Chinook populations were reduced. The catastrophic reductions in Chinook
runs probably brought a biological collapse to much of the Columbia
River basin, both east and west of the Cascades.
River Chinooks were some of the first to be heavily targeted by
commercial fishermen. The mouth of the Sandy is in close proximity to
the largest population area. Nets and fish wheels probably killed most
of the Sandy River Chinook runs before 1880.
salmon hatchery was established on South Boulder Creek, a tributary to
the Salmon River in 1892. This hatchery was to supply Chinook eggs to
bolster the failing Clackamas River runs. Chinook eggs were taken from
mid-July through November. There were fair numbers of fish. But what the
hatchery people found at the mouth of South Boulder Creek in 1892 was
probably no more than the remnant valleys, after the peak runs had been
cropped to extinction. Old records speak of July spawning Chinooks in
both the Sandy and Clackamas drainage's. There is indication that in the
first two years of hatchery operation; peak-spawning activity was in mid
to late August. These upper river runs had severely declined by 1900. By
1906 the runs were so poor that the hatchery was shut down.
1864 the vacuum pack tinned can had been introduced to the Columbia
River. Salmon could now be shipped long distances without fear of
spoilage. Between 1864 and 1877 Chinooks were harvested so intensely
that entire races were completely eradicated.
this 13-year harvest period, the spawning and fry emergence cycles would
have been months longer and much denser than they are now. The overall
food chain must have been immensely richer.
Dam was built on the Sandy River in 1911. It was a huge habitat and
passage problem between 1911 and 1974. It impeded passage and killed
down stream migrating juveniles in huge numbers. During the 1940's the
Sandy River Chinook runs were on the brink of total extinction. Runs had
become nearly intermittent. Some years less than fifty fish returned.
Peak years brought runs numbering in the low hundreds.
1939 until 1951 the fish ladder at Marmot Dam was closed. All anadromous
fish were eliminated from the upper Sandy River basin. Fishery managers
realized that the unscreened flume entrance to the Marmot diversion
canal was a death trap for a very high percentage of down stream
migrating fish. Fish entering the canal eventually had to escape through
the turbines in the Bull Run generators. Mortality was near 100 percent.
Instead of forcing the power company to screen the canal entrance, they
opted to stop migration of anadromous fish above the dam. They trapped
all of the fish and took their eggs to be raised in a hatchery built
below the dam. The project was a disaster. Runs further declined. They
reached a low in 1943 when only 3 female Chinook show up for egg take.
1951 the Marmot flume was screened so as not to entrap juveniles and the
fish ladder was reopened. As Chinooks started to re-enter the basin, the
run timing and spawning activity timing was very critical. This is
because of the small numbers of fish available. Fish that reached sexual
maturity too early or too late had a hard time finding mates.
1974 crucial water flow management improvements on the Sandy River
brought about more favorable conditions for Chinook migration. The
Oregon Department of Fish and Wildlife started an aggressive hatchery
program with upper basin spring Chinook. Up to 420,000 spring Chinook
juveniles are raised at the Clackamas River hatchery and planted in the
Sandy and Salmon Rivers. These are from the lower Willamette stock of
hatchery fish, which are mostly Clackamas River fish. In the 1890's
Sandy River Chinook eggs were used to restart the Clackamas River runs.
Now these same genetics are being used to restart the Sandy River runs.
It's kind of like the genetics were on loan. These Chinooks have in fact
adapted to the Sandy River better than they have adapted to the
Sandy River Chinook runs have prospered
and grew in numbers through the 1980's and 1990's. The run of 1992 was
estimated at 9,200 fish with an escapement of 6,000 spawners. Run timing
has become less critical with both earlier and later returning fish able
to find mates. In the past several years there is indication that our
present spring Chinook runs are stretching out over slightly longer
was primarily a May and June run has now become a March through July
run. Spawning used to be late September. Now some Chinooks are spawning
from early September through late October. The food chain in once again
study of biological science assumes that if there is a niche, then some
organism will fill it. Much of the Chinook habitat in the upper basin is
nearly the same as it was in 1800. If this habitat is maintained in this
same condition, it is reasonable to assume that Chinooks will eventually
exploit all of it. It may be possible to once again have July spawning
Chinooks in the watershed.
…Fall Chinook runs in the Sandy River
basin have increased steadily since 1977… without hatchery
Chinook spawn in the main stem and larger tributaries throughout the
basin. The largest spawning concentration is from the mouth of the Bull
Run River to Dabne Park. These runs are comprised of four genetically
different races of fish. First to come are the Thule Chinooks. These
fish are already colored when they begin to enter the river in late
August. They are done spawning by late September. Next are the later
bright Chinooks. They enter the river beginning in early October and are
done spawning by December. Latest to come are the winter Chinooks. They
enter the river December through January and may spawn as late as
February. Dispersed through the runs are Columbia River Hatchery stray
Chinooks. There has been no other hatchery intervention since 1977.
Recent reductions in commercial harvest have brought better returns of
Sandy River fall Chinooks. However, runs are still far below basin
carrying capacity The 1995 run may have been 3,500 fish, with a basin
carrying capacity of over 10,000.
of the biomass provided by 15,000-20,000 spawners in the upper basin,
rather than 1,500-5,000 spawners....and another 6,500 Chinooks spawning
in the lower river. The food chain in the river would be much richer.
Every Chinook that spawns in the watershed is money in the bank.
To protect and anchor their eggs in the
river bottom, female Chinooks dig depressions in the riverbed with their
tails. These depressions are created by the tail being used as a shovel
and also by the hydraulics being created by the oscillations of the tail
in the water. The eggs are deposited with milt from the male Chinook in
the bottom and trailing edge of the depression. The depression is filled
and the trailing edge is mounded over with a layer of silt free gravel.
This site is called a redd.
redds are often tipped up into the current. The rear interior wall of
the redd is usually composed of sand and silt that has collected down
stream from the digging. In a large excavation this can form a mound
that is three feet higher than the bottom of the depression. The mound
often assumes a shape that is flattened or slightly cupped in the front
and fan shaped at the rear. This mound my be called a sand dune. These
dunes are most prominent in rivers, which carry heavy loads of volcanic
sand, such as the main stem Sandy, Zig Zag and Deschutes below the mouth
of White River. This is because of the availability of building
material. These kinds of rivers have plenty of sand to build mounds.
However this type of structure is also most efficient at keeping the
redd from plugging with sand and destroying the water flow which
oxygenates the buried eggs.
layer of course rock is deposited on the tilted upstream side of this
silt mound. The gravel is chosen so that it builds a strata that is
devoid of silt and water passes trough it easily. This porous strata is
also designed to catch the eggs and milt as they flow from the spawning
fish. This will become the interior of the redd. This is where the eggs
this nursery is deposited a shield consisting of lager and larger
stones. This layer also allows water to pass through it with little
restriction. The heavy rock keeps the redd from eroding.
flows through the front wall of the redd and is deflected by the rear
wall of silt. The water flows into the redd from the bottom and out the
top. This keeps silt from collecting inside the redd and thus insures
the complete oxygenation of the eggs. If the eggs were deposited in a
depression below the level of the riverbed, they would quickly become
buried in sand and smother.
pairs of Chinooks often join redds side by side in rows. The upstream
edge of these elongated dunes often rises steeply from the riverbed. The
upstream face of the dune is composed of course gravel and the backside
is sand and silt. In areas where many Chinooks spawn together these
dunes may form rows which run perpendicular to the current flow. Between
these dunes are trenches filled with soft flows. This wash board contour
slows the water flowing along the bottom of the river. These are favored
resting areas for several species of fish including trout, steelhead and
digging and shaping of Chinook redds creates gravel deposits which can
later be used by smaller fish. Since Chinooks are early fall spawners
the gravel deposits that they create are already prepared for later
spawning species such as steelhead, coho and trout.
…winter steelhead utilizing old Chinook
Spring Chinook dunes in the Salmon River
trap smaller gravel along the edge of the river. In the spring this
gravel is actively sought out by spawning pairs of winter steelhead. In
the lower Sandy River steelhead spawn in the leading top edge of fall
Chinook dunes. The hydraulics created by the dune also keeps their eggs
free from slit.
the Chinook redd is designed to allow water to flow through it, there
are a lot of holes between the rocks which have built it. These holes
are prime habitat for many species of insects such as mayflies, stone
flies and caddis. Chinook spawning areas are very rich in insect life.
Leaches and sculpins are also very prominent in Chinook redds. These
organisms are food for various sizes of larger fish.
records of hatchery egg takes show that the size of returning adult
Chinooks has changed very little over the years. Sandy River basin adult
Chinooks average fourteen to twenty five pounds, with some specimens up
to forty pounds. The average steelhead is seven to eleven pounds. The
average coho is five to eight pounds.
Chinooks are the largest salmonids that
spawn and die in our watersheds
are the largest salmonids that spawn in our watershed. Their larger size
means that they can exploit larger gravel than smaller fish. Big
Chinooks are powerful enough to move grapefruit size rocks around. This
is a different part of the streambed than is utilized by steelhead,
which prefer golf ball size gravel. Resident trout are only large enough
to move marble size stones.
spawn during the lowest flows of the season. This means that they
utilize the center of the streambed. Their fry tend to stay in the
middle, deeper parts of the river. They don't compete for food or space
with other species, which spawn later in the season when river flows are
trout and coho spawn in small tributaries or along the margins of
rivers. Often they spawn in places, which didn't have enough water when
the Chinooks were spawning. Each specie is designed to exploit a
different size of gravel and therefore has different spawning habitat
requirements. Their fry are also genetically designed to exploit this
environment. They usually rear close to the redd through early
development. In this way the fry of different species tend to remain
separated through infancy and don't compete with each other.
trout and steelhead get larger they require more individual space. As
they grow they seek deeper and deeper water. Older fish will often find
holds in the middle of the river. Some of the best holding water is in
the drop-off behind a series of Chinook redds. These areas are often
very rich in insect life. Here there is depth for cover and soft flows
which make living secure and easy. This is also the prime area for
intercepting emerging Chinook fry. Trout and juvenile steelhead migrate
to these areas and there is often enough food and space to support large
numbers. The larger fish rigorously defend the prime spots. Smaller fish
patrol the margins.
…grist for the mill…
The Fly Fishing Shop, Welches, OR
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