By laying eggs in rivers, chum salmon may actually be helping native fish by providing food for them. Biologically speaking, these frigid Arctic waters are not particularly productive. That means there’s usually not enough for native species like Dolly Varden and Arctic char to eat. “When salmon spawn, it’s a natural process that some eggs don’t get buried,” Westley said. “Dolly Varden can eat eggs that wouldn’t survive anyway. So it’s not having a negative impact on the salmon population, but it’s killing Dolly Varden and the fish that live there. It certainly helps us.”
Increasing warming in the Arctic means more liquid water, especially during the critical winter months when water is usually locked up as ice. Liquid water can result from the decomposition of permafrost, essentially frozen soil. (It can also thaw quickly enough to create a hole in the landscape, known as thermokarst.) Thawing permafrost can also allow connections between groundwater springs and surface rivers.
Outside the Arctic, melting glaciers are creating new rivers for salmon to spawn in. This could create more habitat to support more salmon, potentially crowding out native fish species and increasing competition for food and other resources. But for salmon to ultimately succeed in the Arctic, the water must be just right for them to breed and complete their life cycles. “They need liquid water and fish to bring it to them. Also “Animals that require liquid water are culturally important subsistence species,” Lindley said. “They dig nests in gravel, lay their eggs, and hatch them. And there are also very specific temperature requirements that they may have.”
Researchers have been deploying sensors to better understand whether observed spawning areas are within ideal hatching conditions for chum salmon. If water temperatures are suitable for breeding, more salmon may occur, which in turn may affect competition with other species. “Knowing the temperature where the embryo will be is a very important part of the puzzle,” says Westley. “How quickly it happens is related to temperature. So we can estimate very accurately when they will hatch and when they will emerge.”
The Arctic is changing dramatically as it warms, and some of those changes are feeding into brutal climate feedback loops. More tall shrubs can trap more snow on the ground, preventing winter cold from penetrating the soil and staying frozen. This could accelerate permafrost thawing, releasing methane that warms the planet. As the region becomes more fire-prone, wildfires burning in the far north will release more carbon into the atmosphere, further accelerating climate change.
Chum salmon aren’t the only ones adapting to ever-warmer temperatures. “This is just another example. There are a lot of different organisms, both in and out of the ocean, that are changing their habitats as a result of climate change,” said a California scientist who was not involved in the study. said Luis Rocha, curator of fishes at the Academy of Sciences. “It’s happening everywhere, even at the local level. Many species are found in the highlands. The highlands are getting warmer, so the species are moving higher and higher.”
Arctic species that can adapt will do so, while lower latitude species will travel north to take advantage of the new climate regime. Chum salmon may be a harbinger of this change. “Earth, as a planet and as an ecosystem, everything adapts. There’s no way around it,” Rocha says. “The species that are most adaptable to change will survive.”
