Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 8264
Title: Steelhead persistence and adaptation in a warming world
Author: Lisa G. Crozier, Michelle M. McClure
Publication Year: 2015
Journal: The Osprey
Volume: 81
Pages: 9-12
Keywords: Climate impacts, climate change, steelhead, salmonids,

Salmon in general and steelhead in particular are extremely flexible and adaptable animals.  This group of fishes excels at colonizing newly created habitat and adapting locally to complicated dynamics.  As climate change progresses, this diversity might prove decisive in facilitating persistence in our ever-shifting environment.  But can they survive climate change on top of all the pre-existing anthropogenic stressors, and if so, where and how?

The major climatic changes in the freshwater environment that will impact salmon in coming decades are rising temperatures, with greatest increases in mortality risk in summer, and shifts in flow regimes with increased winter flows and intensity of storm events, decreased snowpack with earlier spring freshet, and lower summer minimum flows.  These impacts are similar in direction to many anthropogenic impacts salmon populations already confront, such as loss of connectivity within and between streams and their surrounding landscape, access to cold-water refugia, loss of riparian vegetation, increased flood intensity due to channelization, water withdrawals, and more. 

High priorities for conservation should include restoring the natural processes that keep waters cool and habitats diverse, such as maintaining natural flow regimes and connectivity, restoring riparian vegetation, and maintaining access to thermal refugia.  Protecting thermal refugia in general and from fishing in particular is a key component of preserving a successful summer-run life cycle.  Salmon can become trapped in pools during their migration or during holding periods where they are relatively easy to catch and experience high mortality after handling.  They are at their most vulnerable at these times.

Steelhead will face many challenges in the coming years as temperatures continue to rise, stream flows change, and humans demand more of limited freshwater.  Their chances of persisting are aided by their natural ability to adapt to variable environments, but we must ensure that populations remain as abundant as possible and have access to habitats that are as heterogeneous as possible to foster this resilience.

Theme: Recovery and rebuilding of marine and coastal species
Foci: Describe the relationships between human activities and species recovery, rebuilding and sustainability.
Characterize the population biology of species, and develop and improve methods for predicting the status of populations.