of habitats, potential food, and remediation requirements
in juvenile chinook nursery areas of the Cowichan Estuary.
The Cowichan Estuary, while not a salmon-spawning habitat,
is a critical and important environment for the rearing and
feeding of juvenile chinook and chum, and perhaps coho salmon.
chinook project worked broadly to:
the edges of the estuary and some areas of the mudflats
to assess habitat suitability for chinook juveniles.
what if any rehabilitation is needed to improve habitat
an awareness program
In the Cowichan, as elsewhere, chinook smolts are scattered
along the marsh edges at the highest point reached by the
tide. They then retreat into tidal channels and creeks, which
retain water as the tide retreats. The juvenile chinook occurs
in the estuary from late March to early September, typically
peaking in July and August. Populations dwindle considerably
Due to delays in obtaining project funding, we were unable
to start until early October. We managed to complete most
of our fieldwork before the rains set in and counted our blessings
for so many beautiful days. We were concerned for the change
in seasons and particularly the change in chemical and physical
characteristics of the estuary once the rains started.
Approximately 99% of the accessible estuary edges have been
surveyed, including reclaimed marshes and shorelines, as well
as impacted shorelines and mudflats at 32 Centres over a
distance of 1900 meters. . The habitat survey was conducted
on 0.2km sectors where possible. Each Centre contained one
to four subCentres or transects. Shoreline transect protocols
followed those developed by the Marine Ecology Centre over
the past 8 years. Substrate (bottom) and epibenthic (above
bottom) samples were taken where possible at each of the 95
intertidal sites and at 7 subtidal sites. The samples were
taken at tide levels ranging from just below 2.5 meters up
to 4.5 meters, above sea level. Specifics as to the type of
substrate, plant and animal life were recorded on data sheets
and a series of photos were taken at each transect. We also
assessed each Centre transect for possible future habitat
rehabilitation, if any was required.
Surveyor, David Tattam.
Mudflat sample site.
The goal of this project was to assess the suitability of
various habitats for certain food items of juvenile chinook.
It is recognized that seasonal, tidal, and other factors disallow
any quantative assessment and further that sampling techniques
are not necessarily comparable to the mechanisms used by chinook
juveniles to locate and consume prey.
Field and lab technicians (left to right): Barbera Benoit,
David Tatam and Margaret Walker.
David Tattam and project manager Jackie Hendrix.
Fifty samples each about 6 cm3 (6 cm 2 x 1 cm deep) were analyzed
for potential chinook juvenile prey items (meiofauna). These
samples ranged from the subtidal to the upper intertidal areas
of the estuary. Animals larger than 50 Ám were counted. Counts
ranged from 5 to 4,372 individuals per sample.
Species were identified to broad taxonomic category (e.g.,
nematodes (round worms) copepods (bullet shrimp), ostracods
(clam shrimp), etc.)
Assessment for potential habitat rehabilitation
There are some areas of the estuary that have potential for
of potential rehabilitation:
could be breached
marshes could be re-channeled to allow for better water
flow in and out of the marsh
or re-vegetate certain areas
Downstream deposits from estuary land fill.
Photo of rip rap.
Any habitat rehabilitation in the estuary requires approval
under the CEEMP. Our goal was to assess juvenile chinook nursery
habitat for potential rehabilitation with a view toward obtaining
the necessary approvals and permits for implementation in
Continuing awareness program
painted by two grade 12 students are displayed at the Entrance
to the Marine Ecology Centre. One depicts the life cycle
of Chinook Salmon from birth in the Cowichan River to the
open sea and the return to the Cowichan to breed. The other
displays examples of marine life in the estuary habitat with
emphasis on food sources for Chinook juveniles.