Climate Change Is Affecting Alaska’s Salmon—and Its Bears

Katmai National Park is a realm of untrammeled rivers, pristine streams and clear lakes. The park and the greater Alaska Peninsula are part of the Bristol Bay Watershed, which, according to World Wildlife Fund, is the most productive salmon ecosystem in North America. All five species of Pacific salmon—Chinook, coho, chum, pink and sockeye—spawn and rear in the Bristol Bay Watershed, supporting human cultures and industries and a vast constellation of wildlife. Black bears, caribou, moose, wolves, raptors and other migratory birds all benefit from this bounty.

In fact, in 2019, 56.3 million sockeye salmon returned to Bristol Bay. That year was the fifth consecutive one in which more than 50 million of the fish came back to spawn. The largest run since 1893 happened in 2018, when more than 62.3 million sockeye salmon returned to this rich region.

These salmon support a sustainable economy worth $1.5 billion a year (about 46 percent of the world’s wild sockeye harvest), more than 14,000 American jobs and more than 30 regional Alaska native tribes, which rely on the fish and other subsistence foods for 80 percent of their protein.

Katmai is also home to about 2,200 gloriously fat grizzly bears, who gobble the hefty 4,500-calorie fish—sometimes a dozen an hour—throughout each, fleeting summer.

Climate change is bringing even more of a freshwater buffet to the territory, which could be seen as a boon for the bears. But it’s also altering the lives of the sockeye salmon, which might prove damaging in the long term.

Skipping a freshwater year

Typically, salmon begin their life cycles in clean freshwater streams, spending up to two years in their birthplaces before heading out to the ocean, where they feed and grow to an adult size two to three years later. They then return to their original freshwater homes to spawn and die, which usually happens in late summer or early fall in Katmai. The national park’s bears are used to this plentiful food source.

But according to a study published in the journal Nature Ecology and Evolution by University of Washington researchers on May 27, 2019, sockeye salmon in Alaska’s Bristol Bay Watershed are now more likely to head out to sea after only one year. They’re skipping an entire 12 months in freshwater because climate change has caused lakes and rivers to warm up earlier each spring, fueling the growth of the tiny plankton that juvenile sockeye like to eat. This allows the young fish to grow and put on weight much faster, triggering their migration to the ocean.

Adding in ocean time

But this quicker jump into saltwater doesn’t necessarily benefit salmon in the long run. They’re now spending an additional year in the ocean, taking more time to grow and mature. This extra year at sea is likely caused by climate stressors, as well as other fish: in the ocean, wild sockeye compete for food with close to 6 billion hatchery-raised salmon released each year throughout the North Pacific. That number has grown steadily since the 1970s, when only half-a-billion hatchery salmon were released.

This trend could negatively impact the Bristol Bay sockeye population’s resiliency because before, not every fish in a particular age class would migrate to the ocean in the same year. Any given year would see fish of different ages moving out to sea. But now, most sockeye are migrating at the same time, as one-year-olds. This could devastate an entire age class if ocean conditions happen to be poor one year. On top of that, scientists don’t know how many salmon the North Pacific can actually support.

Minding the Pebble Mine

Unfortunately, that’s not the only challenge the sockeye salmon—and the humans and wildlife that depend on them—will have to navigate.

One of the greatest threats to Alaska salmon is the proposed Pebble Mine located at the headwaters of the Bristol Bay Watershed, beneath Bristol Bay’s two most productive river systems in a seismically active region. If constructed, Pebble would be one of the world’s largest open-pit, copper-gold-molybdenum mines, with an earthen dam 60-stories tall that would ultimately hold up to 10 billion tons of toxic tailings and contaminated water—forever. The mine and tailings lake would sit just north of Iliamna Lake, the largest lake in Alaska and one of the most important sockeye salmon nurseries in the world.

World Wildlife Fund reports that the Environmental Protection Agency estimates that Pebble Mine could grow to be nearly as deep as the Grand Canyon, cover an area larger than Manhattan and fill a major football stadium up to 3,900 times with mine waste. Even without a mine disaster, construction of the Pebble Mine would destroy 94 miles of salmon streams and 5,350 acres of lakes, ponds and wetlands.

If you’d like to read more about the proposed Pebble Mine, see Natural Habitat Adventures guide Brad Josephs’ posts regarding the project in his Bears and Beyond blog. You can also keep up with the latest news by going to the Pebble Watch website.

In 2019, about 14,000 people went to Katmai National Park to view the salmon-fishing bears at Brooks Camp. Most of them would say that it was a privilege to be able to share the grizzly bears’ world even for just a few moments, and that it was an experience that won’t be forgotten. Perhaps by working together, we can keep those hordes of crimson salmon faithfully returning to Alaska’s Bristol Bay Watershed each summer for decades to come.

For us, and for the bears.

Here’s to finding your true places and natural habitats,

Candy