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THE LAKE COWICHAN GAZETTE
WEDNESDAY, SEPTEMBER 10 • 2008
Community
Spawning gravel laid in two short days
River Project’s Success Could Lead To More Fish Habitat Work
BY DOUG MARNER
It took only two days
last week to put 120 cubic
metres of gravel into the
Cowichan River to enhance
chinook salmon spawning
grounds.
Ninety cubic metres
were put into the river
below town hall and
another 30 cubic metres
were put in the river near
the Duck Pond, using a
gravel slinger from Johel
Brothers.
“It went a lot faster
than we thought it would,”
said Craig Wightman, a
fish biologist for the B.C.
Conservation Foundation
who is working on the
project. “The gravel slinger was great. There was
way less impact. It was
very good.”
Without the gravel
slinger, the project would
have required building
a temporary ramp to get
equipment into the river,
which would have taken
much longer, cost more
money and caused a greater disturbance in the river.
On Thursday the gravel bed was map surveyed
so that when the fall rain
comes and the river flow
increases, they can determine how much of the
gravel is washed downstream. Wightman said they
expect some of the gravel
will wash downstream, but
that won’t likely impact the
ability of fish to successfully spawn.
The large gravel that
was put in the river, prime
for chinook, is also good
for steelhead. Wightman
said they’ll be back in
October, in their dry suits
and snorkels, to monitor
spawning.
Then, in the spring
they’ll do more underwater
surveys to see how well the
new gravel holds and how
successful the spawning is.
If things go well, more
gravel could be put in the
river in future projects.
A project description
notes that DFO assessments in 2004-05 show chinook egg-to-fry survivals
were significantly higher
closer to Cowichan Lake,
where water quality was
much improved. A hydraulic sampling of spawning
areas near the Greendale
Trestle found survival rates
of 86 per cent, compared to
no more than a 6.8 per cent
survival rate at three sites
downstream.
Based on 2006 snorkel surveys by the BC
Conservation Foundation
and the Ministry of
Environment, quality gravel deposits were extremely
rare in the Cowichan River
downstream from the weir
in what has traditionally
been highly productive
spawning grounds. The
survey showed that natural
gravel tends to be small
and frequently mixed with
sand, but there is evidence
of salmon and steelhead
use for spawning.
Wightman said the
amount of gravel has
diminished over the last
few decades and last
week’s project looked like
a good chance to supplement the gravel to improve
habitat.
The project is jointly
sponsored by $25,000
from the Pacific Salmon
Commission, Southern
Endowment
Fund;
$20,000 from the Habitat
Conservation
Trust
Foundation; Living Rivers
– Georgia Basin/Vancouver
Island; and in-kind contributions of $5,000 from the
Department of Fisheries
and Oceans and the B.C.
Ministry of Environment.
Dave Leschert, left, of CDW Consulting of Victoria
and fish biologist Jeramy Damborg of the B.C.
Conservation Foundation are at the receiving end of
Doug Marner Photo
the survey instrument.
A gravel slinger, owned by Johel Brothers, sends rocks into the Cowichan River early last week, which will be a
new spawning ground for chinook salmon and steelhead.
Dennis Skalicky Photo
Gord Williams opf CDW Constulting of Victoria uses a survey instrument to do the initial mapping of the new
gravel bed.
Doug Marner Photo