Salmon migration changing faster than expected due to climate change

New research suggests that climate change is affecting when wildflowers and ocean plankton bloom, but its impact on salmon migration is more complex.

The study, published in the journal Nature Ecology & Evolution, involved the collaboration of researchers from Simon Fraser University (SFU) and other North American institutions.

Led by SFU researcher Sam Wilson, the team compiled the world's largest dataset on the timing of juvenile salmon migration, which included 66 populations from Oregon to Alaska.

The data set consisted of records spanning at least 20 years, with the oldest dating back to 1951. In particular, the study focused exclusively on wild salmon, excluding those from hatcheries.

Sam Wilson, lead author of a review conducted by the Salmon Watersheds Lab at SFU and a postdoctoral researcher, emphasizes the importance of long-term monitoring to understand salmon migration patterns.

Wilson highlights the dedicated efforts of field scientists from various organizations who have diligently collected data on smolt migration over the years.

Salmon migration timing changes

The review reveals that the timing of migration for many salmon species has undergone significant changes over the past two decades or more. Among them, pink and chum salmon exhibited the fastest rates of change, migrating seven days earlier per decade.

However, the study found that within-species populations had greater variation in migration timing changes than differences between different salmon species. The unpredictability of these specific population changes could not be explained with the available climatic and geographic data.

Dr Wilson expresses surprise at the results, as while the study shows strong evidence that climate change affects salmon migration, the variation and unpredictability of the changes were unexpected.

The research highlights that, in response to the same level of warming, some populations migrate earlier, some do not, and others migrate later in the year.

Salmon and Climate Change Conservation

Matching the timing of juvenile salmon migrations with the availability of food in the ocean creates favourable conditions for their survival during the initial months, which ultimately affects the number of adults that return.

Researchers are concerned that salmon are not adapting to changes in the coastal ocean, leading to increased mismatches between the timing of migration and food availability, particularly in future climate change scenarios.

Review co-author Dr. Matthew Sloat, and Director of Science at the Wild Salmon Center, highlights the importance of the study in bringing together scientists and data sets from more than 50 government and community organizations to better understand life stage which is often neglected. of salmon

The study underscores the importance of long-term monitoring projects, which are expensive and logistically difficult to execute, but increasingly crucial to advancing our understanding of the impact of climate change on salmon.

Since climate change modifies ecosystems, predicting the most vulnerable species or populations can help prioritize conservation efforts. Study co-author Jonathan Moore highlights the importance of a precautionary management approach for long-term conservation of ecologically, culturally, and economically vital species like Pacific salmon, especially when changes are difficult to predict.

Moore, a professor at SFU's Salmon Watershed Laboratory, emphasizes that climate change is a reality that is transforming salmon and their ecosystems, with many unpredictable changes calling for safeguarding the biodiversity of salmon and their habitats.

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