A new study published on May 1 by Nature Climate Change, a study that is the largest of its kind, has found that salmon migration timing is changing in unexpected ways as a response to climate change. Dr. Eric Ward of NOAA Fisheries’ Northwest Fisheries Science Center was part of a team of more than 50 scientists from government and community organizations across North America who analyzed data from 66 salmon populations over a 70-year span.
“This is the longest, most detailed dataset of its kind and offers a pretty unique picture into the potential response of climate change across salmon species,” said Ward in a news release from the National Oceanic Atmospheric Administration.
The study uncovered that many salmon species have a migration timing that has substantially changed over the last 20 years. Pink and chum salmon had the fastest rate of change, migrating seven days sooner than before. Other species’ average migration timing was unchanged.
However, after further studying the data, researchers found a more significant variation between populations within species than between different salmon species. These population-specific changes were unpredictable with currently available climate and geographic data.
“We were surprised to find that the changes in migration timing were so variable,” said the study’s lead author, Dr. Sam Wilson of Simon Fraser University. “We expected to see a more consistent response to climate change.”
It was found that due to the same level of warming, some populations had an earlier migration while others had no change or even migrated later in the year.
Concerningly, salmon appear not to respond to changes in the coastal ocean, making mismatches more common under future climate change.
An important takeaway from the study is the significance of protecting salmon habitats and ensuring that salmon have access to food. While climate change continues altering ecosystems, study author Dr. Jonathan Moore believes that predicting the species and populations that are most vulnerable and prioritizing their ecosystems is essential.
“Climate change is here, and it is changing salmon and their ecosystems,” said Moore. “Many of these changes are going to be unpredictable, which calls for protecting both salmon biodiversity and their habitats.”
For the complete study, please visit https://www.nature.com/articles/s41559-023-02057-1.