Newhalen River in Alaska’s Bristol Bay.
Braided River Channels: The gravel bottoms and braided channels of rivers leading into Iliamna Lake in southwest Alaska are ideal for the many king salmon that spawn in the lake's waters. © 2008 Ami Vitale

Stories in Alaska

Science to Guide Conservation in Bristol Bay

Explore our Bristol Bay interactive map.

Everything runs on wild salmon in Alaska’s Bristol Bay. Nature runs on salmon. Communities. Business and industry. Salmon is the basis of millennia-old Indigenous tradition. The lands and waters of Bristol Bay produce more wild salmon than anywhere else on Earth and that fuels a sustainable commercial salmon fishery valued at $1 billion annually. 

Bristol Bay is home for half of the Earth’s wild sockeye salmon. Why? It’s the wealth of healthy streams and rivers, wetlands and lakes. This mix of pristine habitat creates a diverse genetic portfolio of several hundred discrete sockeye salmon populations – and this diversity is key to productivity and long-term sustainability. 

Bristol Bay’s portfolio of genetic diversity—much like a diverse investment portfolio – contributes to a more resilient salmon system and bolsters local fishery-dependent economies. Wiping out or harming any of these discrete salmon populations puts the productivity of the larger Bristol Bay salmon system at risk over time.

To protect this globally significant diversity of wild salmon populations and the people who depend on them, The Nature Conservancy has invested in a science-led process to assess the risk of developing the proposed Pebble mine in the headwaters of two of the planet's most productive wild salmon rivers. This research led to an influential 2010 resolution on large-scale mining in Bristol Bay which was authored by the Board of Trustees of The Nature Conservancy in Alaska. The proposed Pebble mine does not meet this standard identified in the resolution and for this reason TNC stands opposed to the project.

See our assessment of the risk of tailings dam failure in Bristol Bay salmon headwaters.

Current Status

The Pebble mine was first proposed more than a decade ago for the headwaters of the Nushagak and Kvichak rivers in Bristol Bay in southwest Alaska. In late 2017, the Pebble Limited Partnership submitted a mine plan in its permit application to the U.S. Army Corps of Engineers. That documentation described plans to fill thousands of acres of wetlands—initiating a formal review process as established by the National Environmental Policy Act, or NEPA.  

The Pebble copper and gold mine proposal calls for an unprecedented level of development for western Alaska, including a 188-mile gas pipeline, a 65-mile road, port infrastructure to support an ore-hauling barge on Lake Iliamna, and a tidewater port site at Amekdedori Creek on the western shore of Cook Inlet located 95 miles southwest of Homer.

The U.S. Army Corps of Engineers released a draft environmental impact statement on February 20, 2019. The public comment period extended through July 1, 2019. Information about the mining proposal is available on the U.S. Army Corps of Engineers Pebble Project EIS website


Our Bristol Bay Interactive Map sheds light on an interconnected and complicated landscape and pulls together data from across the region so that scientists, decision-makers and concerned citizens can see in one place everything from the footprint of the proposed Pebble mine to at-risk salmon streams.

Since the Pebble mine was proposed for the headwaters of the Nushagak and Kvichak rivers in the early 2000s, The Nature Conservancy, tribal environment programs, and other research organizations have compiled thorough inventories of the region’s salmon streams, hydrology, traditional use areas, water quality and more.   

Bristol Bay’s portfolio of genetic diversity – much like a diverse investment portfolio – contributes to a more resilient salmon system and bolsters local fishery-dependent economies.