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Extreme environmental impacts on Pacific salmon

The health of a watershed plays a major role in the strength of salmon populations. Cumulative impacts of our changing climate, extreme weather events and human activities can put salmon at risk. These environmental changes affect Pacific salmon at every stage of their life-cycle, particularly during critical reproduction and early development periods when they rely on freshwater habitats. Because of this, extreme environmental events such as heat-waves, droughts and flooding can have large impacts on these species and make them vulnerable to population declines.

Climate change

Impacts of climate change on Pacific salmon

Climate change is expected to result in more extreme weather events throughout salmon habitats which could lead to deteriorating conditions for salmon in marine areas, freshwater lakes and rivers. Changes such as higher water temperatures, extreme or prolonged drought, increasingly earlier freshets and major fires and floods can impact salmon in a number of ways, including by:

  • limiting or blocking salmon migrations
  • reducing the quality and availability of salmon habitats and food
  • increasing salmon metabolism so they need more food to grow
  • increasing mortality or reducing salmon health and breeding success due to disease and stress
  • exposing salmon to more predators

Climate change and human activities can combine to create extreme environments. As air temperatures rise, lakes, rivers, and streams exposed by development that reduces or removes streamside vegetation become warmer. As rainfall increases, watersheds destabilized through human activities such as land clearing are more likely to reduce fresh water quality in salmon habitats by releasing sediments into waterways. The increased probability of land slide activity due to excess rainfall may also block salmon migration routes and bury spawning gravels. These pathways of effect and impacts to salmon can be even more severe in landscapes altered by major wildfires.

More information is available in our State of the Canadian Pacific Salmon: Responses to Changing Climate and Habitats report.

What we are doing

We recognize that a bold and targeted response with concrete actions is required to address the challenges facing Pacific salmon over the long term. We also know that addressing Pacific salmon declines will require the involvement and work of many Indigenous and rural communities across British Columbia and Yukon; these collaborations have been, and will continue to be, on the front line of salmon conservation.

  • Through the Pacific Salmon Strategy Initiative (PSSI), we are guiding and supporting efforts to conserve and rebuild salmon populations.
  • We are continuing to strengthen our partnerships with First Nations, the governments of British Columbia and Yukon, and non-government organizations to undertake collaborative and strategic planning actions to mitigate and adapt to the impacts of climate change.
  • Our Habitat Restoration Centre of Expertise carries out restoration work directly and provides technical expertise to partners who are undertaking salmon habitat restoration work.
  • We are supporting salmon stewardship and restoration work across B.C. through the joint federal and provincially funded B.C. Salmon Restoration and Innovation Fund (BCSRIF). The current phase of the BCSRIF is considering projects that address climate change impacts to salmon and provide increased opportunities for engaging others in actions that can support salmon rebuilding.

Impacts of drought on Pacific salmon

It is increasingly common for some areas of fish habitat to dry up, or “dewater”, during B.C.’s dry, warm summer months. This can cause salmon or salmon fry to be trapped in isolated pools, which puts them at risk due to:

  • lack of oxygen
  • warm water temperatures
  • lack of food
  • increased exposure to predators

Earlier snow melts, prolonged periods of low rainfall and warm weather can result in drought conditions in which dewatering of fish habitat is more severe, more widespread and has greater impacts on fish populations. Under drought conditions, dewatering of streams and river beds can delay or block salmon migrations to spawning areas needed for reproduction.

Response to 2023 B.C. drought impacts on Pacific salmon

A strong El Niño was predicted for 2023 and an early heatwave on the West Coast significantly reduced mountain snowpack levels that would normally feed many streams and rivers throughout the summer. These conditions are challenging for Pacific salmon and their habitats. We have been closely monitoring conditions and are working with the Province of British Columbia, First Nations, stewardship organizations and other partners to reduce drought impacts on Pacific salmon.

What we are doing

Our experts are working hard to support Pacific salmon during drought in a variety of ways, using the best available scientific advice.

  • We are working closely with the Province of British Columbia and municipalities on strategic and coordinated drought response planning, including flow management.
  • Our Fish and Fish Habitat Protection Program and our Habitat Restoration Centre of Expertise, which includes scientists, biologists, engineers, engineering technicians, monitoring technicians, hydrogeomorphologists and data analysts, are working with stewardship organizations and non-governmental organizations like the Pacific Salmon Foundation to support immediate actions as well as sustainable and effective habitat restoration solutions for the future.
  • We are working with First Nations and local stewardship organizations to relocate high-priority populations of stranded salmon from dewatered areas, to improve or provide alternate passage for salmon through dewatered stream sections, to create or increase cold water refuge habitats and to make other habitat improvements as needed.
  • We are consulting our subject matter experts through a Drought Response Task Team to effectively coordinate drought related activities and support drought recovery planning.
  • We are working with partners to carefully monitor water temperatures and flow levels, as well as Pacific salmon populations in areas most affected by drought conditions.
  • We have implemented and are enforcing salmon fisheries closures to protect at-risk populations.

These are just a few of the actions that we’re taking to support Pacific salmon through difficult drought conditions. Additional work continues year-round through the Pacific Salmon Strategy Initiative (PSSI), the British Columbia Salmon Restoration and Innovation Fund and other programs.


Floods and fish habitat

Within riverine ecosystems, flooding is a natural ecological process. Flooding plays an important role in maintaining functional river channels and fish habitats, by recruiting and depositing gravel, flushing fine sediments and re-establishing side-channel connectivity. Much like forest fires can play an important role in rejuvenating forest ecosystems, flooding can play a similar role in the riverine environment.

However, floods can also pose a risk to salmon by:

  • stranding salmon in pools that become cut-off from rivers
  • destroying salmon eggs
  • damaging salmon habitat
  • forcing juvenile salmon into marine environments prematurely

Extreme weather events are becoming more intense and frequent due to climate change. As rainfall events increase, flooding may become more severe and happen more often, increasing the impacts to salmon and salmon habitats. Re-examining the places and ways in which we undertake development and land use activities is one way people and communities can adapt to a changing climate and improve outcomes for salmon. From a flooding perspective, practices to consider include:

  • avoiding development in high-risk floodplain areas
  • upgrading and realigning dikes and current land use to avoid high value salmon habitats and to accommodate more frequent flood events
  • upgrading aging flood mitigation infrastructure like pump systems and flood gates to fish-friendly designs that maintain safe fish passage while offering improved protection for people and infrastructure during high flow events
  • protecting and restoring off-channel fish habitats and wetlands that can serve to absorb surface water run-off and moderate the effects of flood waters

Response to 2021 B.C. extreme flooding impacts on Pacific salmon

Significant floods in southern British Columbia in November 2021 had a sizable impact on both residents and the local environment. This unprecedented ‘atmospheric river’ event affected the Squamish River watershed, lower Fraser River watershed and the Thompson and Nicola River watersheds near Merritt, as well as rivers and streams on Vancouver Island.

Following the floods, we provided regulatory support and advice for urgent infrastructure works in and near fish habitat, to support protection of people and timely repair of properties. We also worked diligently to safeguard and restore access and function to our enhancement facilities and infrastructure, including spawning channels and off-channel rearing developments requiring restoration.

Given the 2 to 5 year life cycle of Pacific salmon species, impacts of the flooding on fish populations may not be known until 2026.

What we are doing

Improving outcomes for Pacific salmon requires not only building better and stronger protections against flooding, but also more functional and resilient floodplains. We are working with all our partners to promote approaches that not only benefit fish, but also create more resilient communities.

Moving forward

Impacts of climate change, such as recent floods and droughts have been devastating for many. As we continue to better understand their impacts on salmon and other species, we commit to working with our partners in a strategic and coordinated way. Through all our programming, we are working to bring together the expertise required to ensure that salmon recovery and habitat restoration work we undertake is effective and considers the likelihood of future extreme weather impacts.

How you can help

Salmon may be stranded during a drought or after a period of flooding, when the flood water recedes. If you find salmon that you think may be stranded due to extreme weather events, you are encouraged to reach out for help. It is illegal to move salmon or fry to a new system, above a barrier, or to a hatchery without a permit.

Stranded fish

If you discover salmon stranded in disconnected pools of a waterbody, reach out to a local stewardship organization to let them know. These stewards and streamkeepers work with us and have the training and expertise to ensure that the fish are moved to a nearby location within the same immediate water system, which will remain wet throughout the summer and autumn and will not freeze over winter.

Dead fish or disrupted habitats

If you find several dead fish, or the harmful alteration, disruption and destruction of fish habitat, please let us know at or 1-800-465-4336.

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