Extreme environmental impacts on Pacific salmon

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 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 team carries out restoration work throughout B.C. and Yukon and provides technical expertise to partners.

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 2024 B.C. drought impacts on Pacific salmon

B.C. experienced higher winter temperatures and lower precipitation than typical over this past winter. As a result, mountain snowpack levels are at record low levels. This snowpack is needed to feed many of the province’s streams and rivers throughout the summer. Dry conditions increase the risk of forest and wildfires, which further damage spawning habitat and can threaten salmon hatcheries and other physical infrastructure.

We are 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.

Funding and boots-on-the-ground field activities

We dedicate significant resources toward addressing the short- and long-term impacts of drought on fish and fish habitat. This is largely made possible through the Pacific Salmon Strategy Initiative (PSSI), which has given us more capacity and expertise to work with our partners to address environmental impacts to Pacific salmon and their habitat.

We support field activities by providing boots-on-the-ground support, advice and expertise, and / or funding to respond to salmon survival threats during drought. Together with our partners, we:

• relocate stranded high-priority populations from dewatered areas
• improve or provide alternate passage for salmon through dewatered stream sections
• create or increase cold water refuge habitats and provide oxygenation to stranded pools
• support other habitat improvements as needed

We are also engaged in, or supporting, dozens of projects to mitigate the long-term effects of drought and build more drought-resistant ecosystems for the future.

Fisheries decisions

We may adjust salmon fisheries throughout the season due to drought conditions and to meet conservation requirements for salmon stocks.

Supporting implementation of Provincial regulations

The Province of British Columbia’s Ministry of Water Land and Resource Stewardship (WLRS) is the lead authority on water management during drought. We support the province when implementation of their Water Sustainability Act Temporary Protection Orders (TPOs) are required to curtail licensed water use in systems. This decision is taken when low flows will cause significant or irreversible harm to an aquatic ecosystem or fish population.

Monitoring

We track, monitor, and report our activities and debrief internally and with partners to build on our successes and learn from our short comings.

Together with our partners, we monitor drought conditions and fish impacts and share information and expertise at formal and informal meetings tables on:

• river levels
• water temperatures
• fish presence and spawn timing in rivers
• areas where fish are struggling
• other relevant details required to support fish through drought

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.

• We are actively engaged in tripartite flood recovery planning tables. These forums include the Province of B.C., First Nations, academia and non-government organizations, and focus on joint identification of impacts, priorities, actions and resources to support recovery activities.