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Species of the Pacific: Bull Trout

Two fuzzy baby birds with large eyes huddle together on a brown branch, with a green backdrop of tree leaves behind them.

This is post 4 of 4 in "Species of the Pacific."

Throughout this series, we explore the ecosystems in the Pacific Northwest and the wildlife who inhabit them, including the Northern Spotted Owl, the wolverine, and bullhead trout. Our newly launched Pacific Wildway aims to reconnect, restore and rewild the Pacific region so that these species and more can thrive. All posts in this series…

Looking over the edge of a gently sloping cliff in the Gifford Pinchot National Forest, one might see cold fresh water pummeling through rocky substrate. The flowing streams here are crucial; they are carrying a threatened fish downstream.

This national forest in southwestern Washington is among the few locations left in the Pacific Northwest that hosts a population of the rare bull trout, which is struggling to survive. Degraded streams, mining, land management practices, and a historic bounty placed on the fish once thought to be “menacing,” are just some of the factors contributing to habitat fragmentation and the species’ decline.

A small greenish gray fish slides on its belly along a pebbly underwater surface.
A bull trout slides along a pebbly riverbed. Photo: Shannon Downey, USFWS

Bull trout life history patterns vary by each population’s geographic location. Some populations are migratory, meaning they migrate from smaller streams to large rivers and back again to spawn, while other populations live their entire lives in their natal small stream system. Migratory fish are often larger and can reach to over 30 inches in length, whereas the non-migratory are often smaller, more in the range of 10 to 12 inches.

The Plight of the Bull Trout

Like most species that bear the yoke of climate change most acutely, the bull trout faces a combination of persistent threats rather than one major threat. The widespread warming of streams due to human development and climate change is at odds with the bull trout’s conditions for survival.

As a result of severe environmental changes, the once wildly abundant species has diminished in number, and their historic range has contracted significantly.

Because bull trout require very cold water, they inhabit cold streams in high-elevation and mountainous regions. A 2014 study of climate-induced contractions in bull trout range predicts bull trout populations will retreat to higher, cooler thermal refuges as water temperatures increase.

But these cooler thermal refuges are shrinking, as an earlier annual snowmelt and less snow change stream dynamics. The stable riverbanks and the complex and diverse vegetation have been degraded by land management practices, and dams block essential migratory pathways.

Furthermore, intensive logging and land clearing disrupts the stream sediments that bull trout eggs require for long incubation periods. These degraded stream conditions have severely reduced the number of migratory bull trout as water quality parameters fall below the range of desirable conditions. In addition, bull trout’s hybridization and competition with non-native brook trout is diminishing the distinct genetic profile of the threatened species.

As a result of these environmental changes, the once wildly abundant species has diminished in number, and their historic range has contracted significantly. Their historic range spanned from the headwaters of the Yukon River, including the major river basins of Washington and Oregon, with its southernmost point the McCloud River in California.

The U.S. Fish and Wildlife Service reports that bull trout occur in less than half of their historic range in the Columbia River Basin, “with scattered populations in portions of Oregon, Washington, Nevada, Idaho and Montana. In the Klamath River Basin, bull trout occur in 21 percent of their historic range.” They are extinct in California. The decline in abundance contributed to the bull trout’s threatened listing by the USFWS in 1999.

Rewilding the Pacific for the Bull Trout

Although classified as a game species in many areas, including Washington, they are listed as threatened by the federal Endangered Species Act and must be thrown back if caught while fishing.

A man stands in a rushing stream with a forested bank, holding a contraption made of thin metal rods.
A fisheries technician uses radio antenna to track tagged bull trout. Photo: Joel Sartore, USFWS

The habitat degradation that threatens bull trout also plagues salmon. Land management projects being conducted to protect and restore salmon populations will benefit bull trout. These include modernized land management practices that prevent the degradation of stream conditions, including reducing or eliminating timber harvest in riparian corridors, increasing restrictions to curtail harmful mine runoffs, and considering re-introduction efforts.

In 2015, USFWS finalized a bull trout recovery plan that addresses six critical habitat locations and identifies how the USFWS and environmental stakeholders will mitigate loss of habitat connectivity and passage barriers, non-native fish competition and predation, and the effects of poor land-management practices on bull trout populations.

USFWS recognizes bull trout as having the most specific survival conditions of any salmonid, and refers to these conditions as the “Four Cs:” Cold, Clean, Complex and Connected habitat. At Wildlands Network, it’s our mission to reconnect, restore and rewild habitat across North America so that environments can provide the necessary conditions for survival—like the Four Cs for bull trout—for all wildlife, including humans. We believe a connected and rewilded North America is the solution to combat the disastrous effects of climate change.

A white waterfall flows between tall towering pines
The bull trout lives in similar environments to the one pictured above, at Wallace Falls State Park in Washington. Photo: Katy Schaffer

In the Pacific, connected and healthy waterways and riparian areas are an essential part of our new Pacific Wildway. Clean water is a vital need for our species, as it is for all other species, making protecting water and riparian areas a critical aspect of our work here.

Beyond the need for clean drinking water, waterways connect us.  Streams and river systems flow from mountains to urban areas through protected areas and private lands. Increasing protection of riparian corridors will provide essential protection for water, improve fish habitat for bull trout, and could ultimately provide functional connectivity for animals to roam from one core area to the next.

Next time you are near a stream, look into it. Imagine an olive green or grayish blue fish swimming along the current. While seemingly unaffected, its very livelihood is at stake. To support these critical efforts for bull trout and other endangered species, help establish our Pacific Wildway by donating to Wildlands Network.

More posts from Species of the Pacific

  1. Exploring Ecosystems of the Pacific Northwest, March 16, 2018
  2. Species of the Pacific: The Northern Spotted Owl, March 19, 2018
  3. Species of the Pacific: The Wolverine, March 22, 2018
  4. Species of the Pacific: Bull Trout, April 5, 2018

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