Education

Has climate change spared the sockeye salmon?

 By RP Siegel

The subject of climate change has moved from the arena of scientific speculation (and political posturing) to that of everyday news. Most prominent are the storms that have made front page headlines several times this season, demonstrating historic levels of intensity and destruction. But there are many other areas where smaller changes can be observed, changes that while not as significant in isolation, when taken together, paint of picture of large scale transformation…

Wildlife have long served as “canaries in the coal mine,” providing an early indication of changes to come. Kodiak brown bears and sockeye salmon have had a long and nutritious relationship (at least for the bears), which seems to be heading in a new direction, courtesy of climate change.
We’ve all see the videos of the bears standing atop rapids with their mouths open waiting to snatch leaping salmon from mid-air. What you don’t see is how long the bears might have to wait before they catch one. As any fisherman will tell you, catching a fish is no sure thing. What if another food source became available that was more predictable? Might the bears consider changing their diet?
Apparently so. According to a study published in the Proceedings of the National Academy of Science, the warming temperatures have provided a more convenient alternative to the bears in the form of early-ripening berries. It’s not exactly home delivery, but it’s a lot easier than standing in an icy creek all day waiting for a chance to snag a soaring salmon. But the bears are not just lazy either. It turns out that the protein content of these berries is nearly an ideal fit for them nutritionally, allowing them to gain weight quickly. Upon returning to the study area in the Kodiak Wildlife Refuge, lead author, Will Deacy, found “piles of rotting, intact carcasses that had died after spawning instead of being killed by bears.”

A Kodiak brown bear specimen (Lisa Hupp / USFWS, Wikimedia)

The bears, meanwhile, were happily grazing the hillsides and feasting on berries. Deacy refers to the phenomenon as “phenological synchronization.” In other words, different natural processes work on different timetables, some of which are triggered by temperature, while others might be triggered by something else, such as the amount of daylight. Birds, for example, migrate north based on daylight hours, hoping, upon arrival, to catch the newly hatching insects as they emerge to eat young leaves. The insects, however, triggered by temperature, are emerging sooner. What this means is that the birds are now in danger of arriving after the peak of food availability that typically fuels their breeding cycle.

Sockeye salmon get their famously bright red color and hooked nose after they return to freshwater to spawn (USEPA Environmental-Protection-Agency, Flickr)

In the case of the bears, this shift in timing seems like good news for the salmon, since, thanks to the berries, a larger number will survive their trip upstream. However, this is far from the beginning of a new Sockeye Golden Age. First, the salmon all die as soon as they have completed their journey and laid their eggs. And while it might seem that more of them could be successful in doing that, other research conducted by Erika Eliason, a PhD Candidate in Zoology at the University of British Columbia has shown that rising temperatures in areas like Alaska’s Fraser River are approaching levels that are near the “upper limit” for the salmon, threatening their ability to complete the journey. Water in the Fraser River has warmed by two degrees Celsius over the past twenty years. The elevated river temperature increases the probability of cardiovascular collapse during the salmon’s strenuous upstream trek. While most of the salmon are coping thus far, as temperatures continues to rise, laboratory tests show that the fish will not be able to withstand much more without some form of adaptation.
All is not lost, there is evidence that salmon are beginning their migrations earlier, in response to the temperature increase. Nature is remarkably resilient which should provide some hope that if we begin working with it, rather than against it, while also learning from it, we might all stand a better chance of surviving the transition to a warmer climate.

READ MORE: Can clouds save the Great Barrier Reef? by Chris Dalby

about the author
RP Siegel
Skilled writer. Technology, sustainability, engineering, energy, renewables, solar, wind, poverty, water, food. Studied both English Lit.and Engineering at university level. Inventor.