By laying eggs in the rivers, chum salmon could actually help native fish by providing them with food. These cold Arctic waters aren’t particularly biologically productive, meaning there isn’t usually much for native species like dolly varden and Arctic charr to eat. “When salmon spawn, it’s a natural part of the process that there are some eggs that don’t get buried,” Westley says. “The Dolly Varden can eat the eggs, which are not viable anyway. So it doesn’t hurt the salmon stocks, but it definitely helps the Dolly Varden and the fish that live there.”
More warming in the Arctic means more liquid water, especially during the critical winter period when the water is normally trapped as ice. Liquid water can be created by the breakdown of permafrost – essentially frozen ground. (Sometimes it thaws so quickly that it creates holes in the landscape called thermokarst.) Thawing permafrost can also allow connection between groundwater sources and surface flow.
Melting glaciers in regions outside the Arctic are also creating new rivers in which salmon can spawn. This could create more habitat for more salmon, which could displace native fish species or increase competition for food or other resources. But for salmon to ultimately thrive in the Arctic, the water must be just right for them to reproduce and complete their life cycle. “You need liquid water and the fish Also Animals that require liquid water are culturally important subsistence species,” says Lindley. “They dig nests in the gravel, lay their eggs and brood. And there may be very specific temperature requirements that they need.”
The researchers used sensors to get a better idea of whether the spawning sites they observed had ideal incubation conditions for chum salmon. If water temperatures are suitable for reproduction, this could lead to more salmon, which in turn could impact competition with other species. “Knowing the temperature the embryos are in is a really important piece of the puzzle,” says Westley. “How quickly they would develop depends on the temperature. This gives us a really accurate estimate of when they would hatch and when they would emerge.”
The Arctic is changing dramatically as it warms, and some of these changes are creating a brutal climate feedback loop. Taller shrubs are growing more frequently, which could leave more snow stuck on the ground, preventing the winter cold from penetrating the ground and keeping it frozen. This could accelerate permafrost thaw, which in turn would release methane that heats the planet. As the landscape becomes more vulnerable to fire, wildfires in the far north will release even more carbon into the atmosphere, further accelerating climate change.
The chum salmon is by no means alone in its reaction to ever-increasing temperatures. “This is just another example. There are many different organisms in the ocean and outside the ocean that are shifting their range due to climate change,” says Luiz Rocha, curator of fishes at the California Academy of Sciences, who is not involved in the research. “It also happens at the local level, everywhere. There are many species that occur higher in the mountains. The higher altitudes are getting warmer, so the species are moving higher and higher.”
Arctic species that can adapt will do so, while others from lower latitudes will travel north to take advantage of the new climate regime. Chum salmon could be the harbinger of this transformation. “The Earth – as a planet, as an ecosystem – everything will adapt. There’s no way around it,” says Rocha. “The species that adapt best to change are the ones that survive.”