Cowichan Chinook Workshop March 2013

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Cowichan Chinook Workshop March 2013
Cowichan Chinook Workshop
March 2013
Critical Habitats and Key Limiting
Factors
The Next 20 Minutes…
• Critical Habitat & possible
Limiting factors
• Life History Phases
– Adult migration and
Spawning
– Egg to Smolt
• Follow Chinook
Freshwater Life History
Adult Migration - Holding
• Critical Habitat
– Safe adult holding habitats in Lower River
• Possible Limiting Factors
– Excessive predation by pinnipeds in lower
river
Adult Migration – Upstream
Passage
• Habitat Requirement
– Adequate flows to
facilitate upstream
passage
• Possible Limiting
Factors
– Low flows in lower
Cowichan
Adult Migration – Upstream
Passage
• Habitat Requirement
– Unlimited passage
through/around physical
barriers
• Possible Limiting factor
– delays in migration due to
counting fence, Skutz
fishway, Cowichan Lake
fishway, LWD jams or other
barriers
Adult Migration and Spawning –
Water Quality
• Habitat Requirement
– suitable water quality for
adult salmon
• Possible limiting factors
– Low D.O., High
temperatures, High bacterial
counts, other water quality
issues resulting in reduced
fitness or mortality
Adult Migration and Spawning –
Suitable in-river Habitat
• Habitat Requirement
– Deep holding pools,
complex habitat to
provide cover
• Possible limiting factors
– Lack of complex pool
habitat; adequate channel
depth
Adult Migration – Stable River
Morphology
• Habitat Requirements
– stable channel and banks with natural
level of bedload movement
• Possible Limiting Factors
– high bedload deposition in lower river
limits channel capacity and fish
passage, reduces of channel
complexity and increases risk of
channel evulsion and instability
Spawning – Suitable Habitat
• Habitat Requirements
– Sufficient quantity and quality of spawning habitat
• Possible Limiting Factors
– Lack of sufficient gravel recruitment in upper river and
at lake outlet. Impacts of invasive exotics (didymo)
Incubation – Suitable Flow Regime
& Stable Conditions
• Habitat Requirements
– Stable river flows throughout
incubation period
• Possible Limiting Factors
– Freshet flows (egg scour), Low
flows (dewatering of Redds), over-spawn
or other substrate disturbance; predation by fish or birds
Incubation – Substrate Condition
• Habitat Requirements
– Good subsurface water
quality and unrestricted
passage for alevins and
emergent fry through
substrate
• Possible Limiting Factors
– water quality issues, high
sediment loads, compacted
gravel
Rearing/Outmigration –
Unrestricted Passage
• Habitat Requirements
– Unlimited access down mainstem
and into and out of off channel
habitats
• Possible limiting factors
– High spring flows (displacement
of juveniles prematurely), low
spring flows (restrict access to
preferred rearing habitat,
dewatering of habitat, stranding in
off channel habitats), physical
barriers to outmigration.
Rearing/Outmigration – Adequate
Habitat
• Habitat Requirements
– Complexity and cover
in mainstem and off
channel
• Possible Limiting Factors
– Channelization, limited
access to historic off
channel habitats, loss of
complexity throughout lower floodplain, loss of complex
riparian habitat, increased
predation as a result of limited cover availability
Rearing/Outmigration – Adequate
Food Supply
• Habitat Requirements
– Natural sources of
food for rearing fry and
pre-smolts
• Possible Limiting
Factors
– Lack of ecosystem
health and resultant
prey availability
Rearing/Outmigration – Suitable
Water Quality
• Habitat Requirements
– suitable water quality
and temperature
• Possible Limiting
Factors
– high suspended solids,
high temperatures, toxic
conditions
Summary…
• Complex relationship between an
organism and the habitats that support it
• Health of the Cowichan watershed and
river is directly linked to the health of
Cowichan Chinook stocks
• Hopefully this brief overview has provided
you with a starting place and a foundation
for this workshop’s discussion of what
freshwater habitat features may be
limiting to the health of Cowichan Chinook
and possible interventions that could
address some of these limiting factors.

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