200 years ago a father and son in Washington stand along the banks of the Columbia River. They sit in silence, watching the tumbling river rush by, breathing in the fresh air and gorgeous sights. But they’re not there just to appreciate the beautiful day. In their hands, they hold twin fishing rods, though they could have walked down to the river with nothing but their hands and a bucket, and still returned flush with fish. This father and his son are fishing for Chinook salmon, a fish that migrates in schools so abundant it seems as if the river itself was made with salmon, not water. They return home, happy with a bundle of five fish each, while millions of others rush through the water.
Just days later, another father-son pair travel to the Columbia River, but this time they’re hundreds of miles away, in Oregon. They too return home with a bountiful catch, while thousands more pass through the river unimpeded. This pattern continues all across Washington and Oregon, into California, Idaho, and watersheds across the West Coast¹.
This Chinook Population Ratings map was created using data collected and compiled by State of the Salmon – a program of the Wild Salmon Center originally launched in 2003 in partnership with Ecotrust. However, this Chinook Population Ratings map is a secondary compilation of the data and it has not been verified or authorized by Wild Salmon Center.
Over the next couple hundred years, this pattern continues, with generations of families, fisheries, and indigenous tribes depending on these fish as an integral part of their lives². The great-great-granddaughter of one of these families travels to the Columbia River with her father, just like generations before had done. But this time something is different. Though they’ve brought along their fishing rods, their bait, and anything they could need to catch salmon, the fish just aren’t biting. The river is no longer teeming with populations in the millions, the water no longer camouflaged by the countless bodies of salmon. The pair leaves defeated, with a bare catch that pales in comparison to the bounty of the years before them.
In the last 40 years, Chinook salmon have lost 60% of their population, with some schools at 10% of their historic numbers³. There are a variety of reasons why salmon populations are struggling, from habitat loss or degradation and harvest rates to hatchery influence and dams creating new barriers³.
One of the most pressing is the changing temperatures of the waters they inhabit. As the climate warms, the world’s watersheds warm along with them, with scientists projecting average temperatures to experience a 6.9°C increase by the end of the century(4). Projections estimate that the effect of increasing temperature alone could reduce populations by almost 20% in the next 40 years². The problem gets even worse in the open ocean. Salmon spend most of their life in saltwater, returning to rivers and freshwater only to breed. One study found that the dominant driver towards extinction was increasing sea surface temperature, which could lead to a 90% decline in populations, almost guaranteed extinction².
Image Courtesy of Vince Mig
Salmon are so sensitive to increasing temperatures, not just because they prefer Christmas over the 4th of July, but because their fundamental processes of life depend upon temperature. Fish are part of a group known as ectotherms, commonly referred to as cold-blooded animals. They don’t actually have cold blood, but instead rely on the external environment to dictate the temperature inside their bodies. When a human walks outside on a really hot day, something like 115℉, our body temperature stays a cool 98℉. But if a fish were exposed to those same conditions, their body temperature really would reach close to 115℉.
In the same way humans begin to lose functioning and face potentially lethal consequences if they have a fever that becomes too high, salmon struggle to survive in high temperatures. Everyone remembers the classic fact – “the mitochondria is the powerhouse of the cell” from their middle school days. But what does that actually mean? The mitochondria are responsible for the production of a molecule known as ATP, which all the cells in your body use as their source of energy. They produce the power your cells use to function. Without ATP, death would be almost instantaneous for any living thing. The process of creating this ATP is known as metabolism.
Metabolism is one of those biological processes that are impacted by the environmental temperature. Energy is first directed toward basic requirements for survival – things like breathing and circulating blood. Any excess energy is then able to be used to do things- move, eat, reproduce, and more. But as temperatures rise, salmon are required to put more energy into just staying alive, leaving less available for actual use(5).
Image Courtesy of Andrea Stöckel
¹
Pacific salmon populations across North America are dealing with the effects of heat stress – they have less energy to expend, at a time in their life when they need it the most. Without enough energy future generations can’t survive, and the results are plain to see. The great-granddaughter of our original fisher is living in a world with salmon populations that are barely an echo of the abundance they once had. Her great-granddaughter may live in a world without any salmon at all.
Citations
- Salmon Life Cycle and Seasonal Fishery Planning. (2022, June 10). NOAA. https://www.fisheries.noaa.gov/west-coast/sustainable-fisheries/salmon-life-cycle-and-seasonal-fishery-planning
- Crozier, L. G., Burke, B. J., Chasco, B. E., Widener, D. L., & Zabel, R. W. (2021). Climate change threatens Chinook salmon throughout their life cycle. Communications Biology, 4(1), 1–14. https://doi.org/10.1038/s42003-021-01734-w
- Chinook Salmon. (2013, April 29). US EPA. https://www.epa.gov/salish-sea/chinook-salmon
- Betts, R. A., Collins, M., Hemming, D. L., Jones, C. D., Lowe, J. A., & Sanderson, M. G. (2011). When could global warming reach 4°C? Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 369(1934), 67–84. https://doi.org/10.1098/rsta.2010.0292
- Poletto, J. B., Cocherell, D. E., Baird, S. E., Nguyen, T. X., Cabrera-Stagno, V., Farrell, A. P., & Fangue, N. A. (2017). Unusual aerobic performance at high temperatures in juvenile Chinook salmon, Oncorhynchus tshawytscha. Conservation Physiology, 5(1), cow067. https://doi.org/10.1093/conphys/cow067