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Food, Health, and Eco-news
Warming Oceans Could Help Some Salmon Thrive
A new study finds that pink salmon populations are expanding into new territories and growing quickly as climate change opens new spawning grounds. 03/08/2021 by Nathaniel Scharping

In ecosystems around the world, climate change is creating winners and losers. While some species struggle to adapt to changing conditions, others are expanding their territory as the globe warms. And it looks like a particular species of salmon may be among the winners.

ink sketch of pink humpback salmon
Male pink salmon develop a distinctive “hump” made of connective tissue during spawning.

A new study looking at wild Alaskan pink salmon — one of the five species of Pacific salmon in North America — finds these fish, also known as “humpies” due to the males’ distinctive humped back, are moving farther north in the Arctic than ever before. The salmon are showing up in remote northern rivers far from their traditional spawning grounds. After analyzing data on temperatures and salmon populations in Alaska, the researchers say warmer waters are allowing the salmon to push into remote northern rivers far from their traditional spawning grounds.

While global warming is far from an unalloyed blessing – more on that later - this could be good news for both indigenous tribes in Alaska that rely on the fish, and for salmon-lovers generally. Pink salmon are known for a mild flavor and silky texture, making them an under-appreciated gem for seafood aficionados. If record catches in recent years are any indication, pink salmon will continue to thrive on menus and become more abundant in freezers. (Read more: Meet Your Salmon)

Salmon Benefit from Climate Change?

Climate change is making the whole world hotter. But the biggest changes are happening in the Arctic and Antarctic. Studies show the frigid Arctic is warming at two to three times the rate of the rest of the planet (Francis et al., 2017). That’s already causing warmer waters and steadily diminishing sea ice coverage at the top of the world. As a result, sea levels are rising and major ocean currents are shifting, among other significant disruptions to our planet’s environment. But, for some species that live in northern waters, this also means regions that were previously too cold for them are fast becoming habitable.

Millions of salmon are already harvested sustainably from Alaska’s coasts and rivers every year. The state boasts some of the cleanest waters in the world, and well-managed fisheries like the ones Vital Choice sources from ensure that wild populations remain strong. Places like Bristol Bay, in the state’s southern part, and the Yukon, Kenai, Kasilof and other rivers, see multiple runs of all five North American Pacific salmon species every year. But now, salmon are appearing in greater numbers in places where they were rarely seen in past decades (Dunmall et al., 2013). Pink salmon, the smallest and most abundant species, could stand to gain the most.

Pink salmon (Oncorhynchus gorbuscha), are found all along Alaska’s coast, from the Gulf of Alaska to the Chukchi Sea and even farther north. But their numbers in remote Arctic regions have been steadily ticking upward recently. The pink salmon harvest in Norton Bay, which sits about halfway up Alaska’s western coast, has approached or broken records multiple times in the past decade. And the species is appearing with more frequency in even more remote locations.

Salmon on the Move

Recent reports also list pink salmon in Paulatuk, along Alaska’s far northern coast, and even as far east as Greenland. As sea ice shrinks and the waters get warmer, conditions are fast becoming ideal for salmon, letting them greatly expand their territory (Nielsen et al., 2012). Now, this new study provides more evidence that warming conditions are indeed good for pink salmon, tying warmer temperatures in Alaska to expanded runs and larger fish.

glacier in Alaska
As ice covers break up earlier in the season due to ocean warming, pink salmon are becoming more numerous, and their territories larger.

A team led by researchers from the National Oceanic and Atmospheric Administration (NOAA) looked at temperatures in Alaska between 1995 and 2018, and compared them to the number of pink salmon counted in the Yukon River and Norton Sound. Warmer temperatures are correlated with more abundant pink salmon, they say, as well as with fish that grow more quickly. The findings back up recent reports that salmon are becoming more common farther north, and hint that the coming years could see the fish moving north in even greater numbers.

There are two main reasons for the increase in salmon numbers, the researchers say. The first is that more pink salmon are spawning in northern regions where they were rarely seen in the past. Secondly, scientists think warmer ocean waters let juvenile salmon grow larger more quickly, something that could increase their survival rates in the ocean. That means more pink salmon return to spawn, further expanding populations.

And as waters warm even more, new spawning grounds far to the north could become available for pink salmon in places that were previously too cold. That could let the population grow even more in the coming years.

Warming Makes New Genetic Groups

The researchers also noted that warming waters had different effects on the two separate populations of pink salmon. The species spawns every two years, like clockwork, and it’s resulted in two genetically distinct populations. Even-year pink salmon typically do better in the cold, something that probably dates back thousands of years to the last ice age, when the even-year group survived much farther north than their odd-year counterparts (Beacham et al., 1988). Today, fishermen and scientists know that even-year pink salmon are usually found at higher latitudes.

But that pattern could be changing. In Norton Sound, one of the largest pink salmon harvests came in 2017, an odd year (Cotton et al., 2018). More than two million fish were harvested, compared to less than a million in most years. It points to what could be a shifting dynamic in the region, the researchers say, as odd-year pink salmon move into waters formerly too cold for them. Meanwhile, even-year salmon could be ranging even farther north, into places where no pink salmon have lived before in modern times.

More Research Needed

The researchers note that their datasets are incomplete at the moment, something that could interfere with the quality of their analysis. And some of their data seems to contradict other findings, such as evidence that juvenile salmon in their dataset were actually smaller when waters were warmer. More research is needed to get a better understanding of how warmer oceans will impact salmon and other species in the Arctic Ocean and beyond. Still, they say the larger trends appear clear: Warmer oceans mean more salmon, and in places they’ve never shown up before.

While pink salmon may appear to benefit the most from warmer waters, it’s likely that we’ll see numerous salmon species moving northward in coming years. Popular commercial species like king and sockeye salmon may also find new spawning grounds opening up as once-frigid streams begin gradually to warm. That might mean larger harvests all around, and more robust salmon populations.

But, we shouldn’t forget that climate change brings with it a whole host of dangers, some obvious, some still unclear. The oceans are getting more acidic, for example, and changing water temperatures can affect species further down the food chain that salmon feed on. Though salmon may be exploring new territory soon, their future still needs protection from threats of all kinds. That’s why it’s important to always know where your seafood comes from, and buy only from suppliers committed to sourcing from the most sustainable fisheries.

Sources:

  • Andrews AG, E. Farley, Moss JH, J. Murphy, Husoe EF. Energy Density and Length of Juvenile Pink Salmon Oncorhynchus gorbuscha in the Eastern Bering Sea from 2004 to 2007: A Period of Relatively Warm and Cool Sea Surface Temperatures. North Pacific Anadromous Fish Commission Bulletin Number 5 (2009) https://npafc.org/wp-content/uploads/Bulletins/Bulletin-5/NPAFC_Bull_5_183-189Andrews.pdf
  • Beacham TD, Murray CB. Variation in developmental biology of pink salmon (Oncorhynchus gorbuscha) in British Columbia. Canadian Journal of Zoology. 1988;66(12):2634-2648. doi:10.1139/z88-388
  • Cotton S, Bowers F, Menard J, et al. Alaska Department of Fish and Game Division of Commercial Fisheries News Release; 2018. Accessed March 1, 2021. https://www.adfg.alaska.gov/static/applications/dcfnewsrelease/997457402.pdf
  • Dunmall K, Reist J, Carmack E, Docker M. Pacific Salmon in the Arctic: Harbingers of Change. ResearchGate. Published March 2013. Accessed March 1, 2021. https://www.researchgate.net/publication/272567234_Pacific_Salmon_in_the_Arctic_Harbingers_of_Change
  • Farley EV, Murphy JM, Cieciel K, Rand P. Response of Pink salmon to climate warming in the northern Bering Sea. ResearchGate. Deep Sea Research Part II Topical Studies in Oceanography. 2020;177:104830 DOI: 10.1016/j.dsr2.2020.104830
  • Francis JA, Vavrus SJ, Cohen J. Amplified Arctic warming and mid-latitude weather: new perspectives on emerging connections. Wiley Interdisciplinary Reviews: Climate Change. 2017;8(5):e474. doi:10.1002/wcc.474
  • Nielsen JL, Ruggerone GT, Zimmerman CE. Adaptive strategies and life history characteristics in a warming climate: Salmon in the Arctic? Environmental Biology of Fishes. 2012;96(10-11):1187-1226. doi:10.1007/s10641-012-0082-6
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