Salmon Global Warming | Salmon Climate Change | Salmon Threats 

Salmon and Global Warming 


The steeply rising trajectory of carbon dioxide emissions, ocean acidification and increasing  global warming temperatures pose formidable threats to salmon populations.  As more scientific research findings are published, these findings are giving rise not only to concerns about the impacts on salmon species and the industries that harvest salmon but also concerns about repercussions tightening the availability and supply of high demand commercial byproducts of salmon such as fish oil, Omega-3 supplements, DHA, EPAAstaxanthin, DMAE and others.  Here are some of the key areas of concern identified by marine biologists, chemists, oceanographers and other scientists:
  • Increasing concentrations of carbon dioxide are transferring out of the atmosphere and into the ocean causing oceans to become more acidic.
  • As more CO2 is discharged into the atmosphere, the resulting higher acidity levels created in the oceans threaten the destruction of marine organisms that salmon feed on.
  • The shells of microscopic plankton and other tiny marine life that salmon feed on are highly susceptible to dissolving in the increasingly corrosive waters of more acidic oceans.
  • As the salmon migrate from seawater to freshwater rivers for spawning, those freshwater environments are becoming warmer.
  • Because diseases and parasites infecting salmon tend to flourish in warmer waters, salmon will be at increasingly higher risk.
  • Higher global warming temperatures cause winter precipitation to fall more as rain rather than snow which swells and intensifies winter stream flows.
  • More intense winter stream flows flush streambeds, damage spawning nests and hose away incubating salmon eggs.
  • Earlier seasonal spring stream flows expose immature salmon to higher risks of being eaten by predators adding further stress to diminishing salmon populations.
  • As the rising temperatures of global warming shrink the winter snowpack, the runoff that sustains river flows and allows salmon to reach and return from the ocean is reduced.
  • In summer, higher global warming temperatures cause stream flows to decline causing salmon habitats to shrink further.
  • The growing number of dead zones in the ocean (areas in the ocean where there is little or no oxygen) pose a threat to salmon and other fish that enter the zones.

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The quantity of carbon dioxide we've put in the ocean is now well over 500 billion tons. (1)  

— Dr. Peter Brewer,
Monterey Bay Aquarium Research Institute
Monterey, California

As billions of tons of the carbon in the gas pour from industrial emissions into the ocean, it is causing 'the most dramatic changes in marine chemistry in the past 650,000 years.' (2)  

 — Dr. Richard Feely
Pacific Marine Environmental Laboratory
Seattle, Washington

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Higher ocean acidity threatens to dissolve the protective shells of plankton that salmon feed on.  “Organisms that build their shells of calcium carbonate are known as marine calcifiers, and they include the microscopic plankton creatures called coccolithophores and the foraminifera -- or forams, as they're known -- that exist in the seas by the millions at the base of the marine food chain.  

[These microscopic plankton] are a major food source supporting fish like salmon, mackerel and cod, and the shells of the calcifiers are highly susceptible to dissolving in the increasingly corrosive acid waters,’ said Victoria Fabry, a biological oceanographer at Cal State San Marcos.” 

[See video of shells dissolving]

(David Perlman, San Francisco Chronicle Science Editor, “Greenhouse gas turning oceans acidic,” San Francisco Chronicle, Thursday, July 6, 2006 citing Kleypas, J.A., R.A. Feely, V.J. Fabry, C. Langdon, C.L. Sabine, and L.L. Robbins, 2006. Impacts of Ocean Acidification on Coral Reefs and Other Marine Calcifiers: A Guide for Future Research, report of a workshop held 18–20 April 2005, St. Petersburg, Florida, sponsored by NSF, NOAA, and the USGS, 88 pp.) 

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Unlike any possible controversy over global warming, as you increase carbon dioxide in the atmosphere, you're driving carbon into the oceans and increasing the ocean's acidity -- and this is not debatable. (3)

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Acidic waters dissolve shells of tiny marine snails that Alaska's juvenile pink salmon depend on for 60 percent of their food supply.  “Corrosive waters can dissolve clam shells, eat away at corals and kill fish eggs. Already, scientists have taken pteropods, tiny marine snails [view photos of pteropods and a brief video of a pteropod] that swim in the open ocean, from the Gulf of Alaska and exposed them to slightly acidified marine water in a laboratory. Their protective shells immediately dissolved.  

Those creatures make up 60 percent of the food for Alaska's juvenile pink salmon.  Similar creatures support many of the major fish species in Alaska's North Pacific, which in turn supports the billion-dollar Seattle-based industry that provides half the nation's catch of fish." (Craig Welch, Seattle Times environment reporter, “Oysters in deep trouble: Is Pacific Ocean's chemistry killing sea life?,” Corrected version, Seattle Times, Seattle, Washington, Monday, June 15, 2009) 

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The fish we depend on — salmon and pollock and herring — when they're in the first year of their life, they all depend on shellfish for survival. Early models suggest a 10 percent loss in pteropods can cause a 20 percent loss in weight of a fish. (3)

 — Dr. Richard Feely
Pacific Marine Environmental Laboratory
Seattle, Washington

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More than 500 billion tons of CO2 have been deposited into the ocean.  “The quantity of carbon dioxide we've put in the ocean is now well over 500 billion tons. And you can't just transfer that much mass without making changes in the physical properties, as well as the biological properties. . .  We're all in a bind here. You know, there - it's going to be very hard to maintain this number of people on the planet and not have these problems. It worries me that scientists sound the alarm but don't come up with solutions.”  (Dr. Peter Brewer, Senior Scientist, Monterey Bay Aquarium Research Institute quoted in Richard Harris, “Acid In The Oceans: A Growing Threat To Sea Life,” NPR All Things Considered, August 12, 2009) 

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Salmon spawning nests are damaged by higher winter rains and streamflow.  “Climate change affects salmon throughout their life stages and poses an additional stress. As more winter precipitation falls as rain rather than snow, higher winter streamflows scour streambeds, damaging spawning nests and washing away incubating eggs.” (U.S. Global Change Research Program, Global Climate Change Impacts in the United States, Thomas R. Karl, Jerry M. Melillo, and Thomas C. Peterson, (eds.). Cambridge University Press, Cambridge, Massachusetts, 2009, p. 137

Wild Chinook salmon populations are projected to decline by 20% - 40% by 2050 in Washington’s Snohomish River Basin.  “Global warming is expected to further weaken wild chinook salmon populations by changing the temperatures and flows of major river systems, according to a study [Projected impacts of climate change on salmon habitat restoration] published Thursday [April 5, 2007] by the National Academy of Sciences. Warmer waters in the summer and early fall are expected to cause more disease, stress and die-offs, while rain-swollen rivers in warmer winter months could flush out salmon eggs from spawning gravel. . . The study focused on the effects of global warming on the chinook populations of Washington's Snohomish River basin

The researchers concluded that by 2050 wild chinook populations would decline by 20 percent to 40 percent in the Snohomish [view map of projected decline areas in the Snohomish River Basin] The range of decline depends on which of two computer models was used in the analysis. . .  Though the authors questioned the accuracy of salmon-recovery plans that did not account for global warming, they still found plenty of value in restoration efforts. 

In the Snohomish basin, a full-scale restoration that would include tree planting, dike removal and other efforts could reduce the climate-induced chinook decline to only 5 percent by 2050, according to one computer forecast model. In the other model, the restoration efforts were forecast to result in a 19 percent gain in spawning populations. ‘That was the encouraging and surprising result for us,’ [said Mary Ruckelshaus, a National Oceanic and Atmospheric Administration (NOAA) fisheries scientist who was one of seven co-authors of the study]. ‘The restoration plans — if they are carried out — can make a difference.’”

(Hal Bernton, Seattle Times staff reporter, 206-464-2581, “Global warming could deal big blow to salmon,” Seattle Times, Seattle, Washington, Friday, April 6, 2007 citing findings published in James Battin, Matthew W. Wiley, Mary H. Ruckelshaus, Richard N. Palmer, Elizabeth Korb, Krista K. Bartz, and Hiroo Imaki, Projected impacts of climate change on salmon habitat restoration, published online before print April 5, 2007, doi: 10.1073/ pnas.0701685104, Proceedings of the National Academy of Sciences - PNAS, Washington, D.C., April 17, 2007 Vol. 104, No. 16, pp. 6720-6725)

Ocean dead zones off the Pacific Northwest coast pose higher risks to salmon.  “Lower levels of oxygen in the Earth's oceans [hypoxia areas], particularly off the United States' Pacific Northwest coast, could be another sign of fundamental changes linked to global climate change, scientists say. . . In some spots off Washington state and Oregon, the almost complete absence of oxygen [ocean ‘dead zones’] has left piles of Dungeness crab carcasses littering the ocean floor, killed off 25-year-old sea stars, crippled colonies of sea anemones and produced mats of potentially noxious bacteria that thrive in such conditions. . . . Bottom-dwelling species could be at the greatest risk because they move slowly and might not be able to escape the lower oxygen levels.

Most fish can swim out of danger. Some species, however, such as chinook salmon, may have to start swimming at shallower depths than they're used to. Whether the low oxygen zones will change salmon migration routes is unclear. . . . [Low oxygen ‘hypoxia’ areas] appear to be spreading . . . covering more square miles, creeping toward the surface and in some places, such as the Pacific Northwest , encroaching on the continental shelf within sight of the coastline. (Les Blumenthal, McClatchy Newspapers, “Growing low-oxygen zones in oceans worry scientists,” McClatchy Newspapers, Sunday, March 7, 2010)  View video about ocean dead zones off the Pacific Northwest coast.

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“Now would be a good time to enjoy seafood while you can.  It may not be around forever.” (4)

— Joanne Colan
Commenting on the impact of ocean dead zones
on sea life and the availability of seafood

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Warmer oceans will prevent nutrients in deeper waters from reaching ocean surfaces to feed the phytoplankton that salmon feed upon.  Oceans have been getting warmer since the late 1990s. Warmer oceans are hard on phytoplankton [which salmon feed on].  As water warms, it becomes lighter or less dense, and it floats essentially above the deep, cold, dense water.  As ocean temperatures increase, the warmer water on the surface acts as a lid, which prevents the nutrients in deeper ocean waters from being delivered to the surface and fertilizing the phytoplankton that fish like salmon feed on. (Richard Harris, “Warming Oceans Less Hospitable for Plant Life,” NPR Morning Edition, December 7, 2006)  Listen to this NPR story by Richard Harris

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“If you like to eat wild-caught salmon, get ready for some wild prices.” (5)

— Alex Chadwick
National Public Radio

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Escalating prices of wild salmon are being driven up by depleted populations of Pacific Chinook salmon.  “If you like to eat wild-caught salmon, get ready for some wild prices. Stocks of the fish are dwindling off the coast of California and Oregon. There may be a ban on commercial fishing in the region. Now fishing boats in Alaska and Washington will still troll for salmon, but no one expects that supply to meet the demand. We could see wild salmon at 30 dollars a pound. . . . 

[The low supply and consequent high price of salmon is] because the population of Chinook salmon in the Pacific Ocean has mysteriously dried up.  Theories abound from polluted water to climate change, but the bottom line is that spawning numbers were too low this year in the Sacramento River.  So the Pacific Fishery Management Council recently announced that one of its restriction options this year is to completely close the salmon season in California and Oregon.”  (David Gorn, “Salmon Prices to Skyrocket,” NPR Day to Day, March 26, 2008)  Listen to this NPR story by David Gorn

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"[B]usiness as usual means that in 50 years there may be no coral reefs and no commercial fishing because the fish will simply be gone." (6)  

Sylvia Earle
Former chief scientist,
National Oceanic and Atmospheric Admin.

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Impacts of Climate Change on Freshwater Salmon Habitat

August Mean Surface Air Temperature and Maximum Stream Temperature 

Historical (1970-1999) 

2040s Medium(A1B)

mantua salmon habitat climate change washington state

*Projections are compared with 1970-1999 average 

Shrinking Habitats for Salmon and Other Coldwater Fish

Habitat for salmon, trout and steelhead fish are likely to decrease dramatically as a result of higher greenhouse gas temperatures.  “Increasing air temperatures lead to rising water temperatures, which increase stress on coldwater fish such as trout, salmon, and steelhead.  August average air temperature above 70°F is a threshold above which these fish are severely stressed.  Projected temperatures [in the Pacific Northwest U.S.] for the 2020s and 2040s under a higher [greenhouse gas] emissions scenario suggest that the habitat for these fish is likely to decrease dramatically.” (U.S. Global Change Research Program - USGCRP, Global Climate Change Impacts in the United States, Thomas R. Karl, Jerry M. Melillo, and Thomas C. Peterson, (eds.). Cambridge University Press, Cambridge, Massachusetts, 2009, p. 137, Climate Impacts Group, University of Washington, Seattle)

salmon habitat global warming

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ocean dead zone map

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Salmon Tributes

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(1) Dr. Peter Brewer, Senior Scientist, Monterey Bay Aquarium Research Institute quoted in Richard Harris, “Acid In The Oceans: A Growing Threat To Sea Life,” NPR All Things Considered, August 12, 2009
(2) David Perlman, San Francisco Chronicle Science Editor, “Greenhouse gas turning oceans acidic,” San Francisco Chronicle, Thursday, July 6, 2006 citing Kleypas, J.A., R.A. Feely, V.J. Fabry, C. Langdon, C.L. Sabine, and L.L. Robbins, 2006. Impacts of Ocean Acidification on Coral Reefs and Other Marine Calcifiers: A Guide for Future Research, report of a workshop held 18–20 April 2005, St. Petersburg, Florida, sponsored by NSF, NOAA, and the USGS, 88 pp.
(3) Craig Welch, Seattle Times environment reporter, “Oysters in deep trouble: Is Pacific Ocean's chemistry killing sea life?,” Corrected version, Seattle Times, Seattle, Washington, Monday, June 15, 2009, page updated at 11:38 AM
(4) Joanne Colan, News Correspondent, “Dead Zones,” RocketBoom, November 21, 2008, Video track 2:16
(5) David Gorn, “Salmon Prices to Skyrocket,” NPR Day to Day, March 26, 2008
(6) Sylvia Earle, former chief scientist for the U.S. National Oceanic and Atmospheric Administration,"How to protect the oceans," TEDTalks, Long Beach, California, February 19, 2009, Track 12:11)

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