Salish Sea Marine Survival Project

Why are salmon and steelhead dying in the Salish Sea?

Project Overview

The Salish Sea Marine Survival Project (SSMSP) united U.S. and Canadian researchers to determine why juvenile Chinook, coho, and steelhead are dying in our combined waters of Puget Sound and the Strait of Georgia, collectively known as the Salish Sea. From 2014 to 2021, Long Live the Kings, in partnership with the Pacific Salmon Foundation of Canada, coordinated more than 60 organizations in a holistic study of the physical, chemical, and biological factors impacting salmon and steelhead survival. In 2021, the SSMSP published a Synthesis Report summarizing key findings from dozens of studies. The central conclusions identified two overarching phenomena, along with interrelated local effects, driving the decline in Salish Sea marine survival: changing food supply driven by climate and environmental shifts, and increased numbers of predators. This project has become a model for ecosystem-scale collaborative science. With the completion of the main research phase, the SSMSP continues as LLTK and our partners on both sides of the border pursue further studies and pilot solutions to facilitate smarter management and stronger returns.

The Problem

The marine survival of Chinook and coho salmon and steelhead populations in the Salish Sea have declined by up to 90%, and their abundance remains well below what it was 40 years ago. This is despite considerable investments in hatchery and harvest reform and in habitat protection and restoration.  Salmon populations in coastal rivers have not shown the same declines, suggesting that the problem lies with factors within the Salish Sea—the combined waters of Puget Sound and the Strait of Georgia. The loss of salmon threatens the heart of Pacific Northwest culture, the health of our local sea, a multi-billion-dollar fishing industry, and deeply rooted Native American traditions and treaty rights.

The Salish Sea ecosystem has changed significantly over the past 40 years, and the problems our salmon face are due to the interaction of many overlapping factors. The SSMSP researched 21 hypotheses about potential factors influencing juvenile salmon survival. These include changing water temperatures, reductions in food supply such as plankton and forage fish, marine mammal increases, contaminants, and disease, to name a few. The project assessed and prioritized these factors through comprehensive, multi-disciplinary, and trans-boundary ecosystem research. Overall, the evidence supports the conclusion that multiple factors across the ecosystem are affecting Salish Sea salmon. While no single change is solely responsible for the decline, two phenomena emerged as the most significant problems for juvenile salmon: changes to the food supply, and a dramatic increase in predators.

Our Solution

Established in 2014 by Long Live the Kings and the Pacific Salmon Foundation, the Salish Sea Marine Survival Project brought together an international team of scientists and managers from dozens of federal, state, tribal, academic, private, and nonprofit organizations to determine why juvenile salmon and steelhead are dying in the Salish Sea. During the research phase, more than 200 researchers assessed young salmon and steelhead growth, health, and diet; tracked fish and marine mammal movements; monitored marine conditions; and developed innovative technologies to answer critical questions facing salmon recovery and sustainable fisheries. With the publication of the Synthesis Report in 2021, we are moving forward to put this science into action.

Study results and new tools will be used to implement real-world actions that improve hatchery, harvest, and ecosystem management and inform habitat protection and restoration. Along the way, we are ensuring that the findings of this comprehensive ecological effort broadly inform Salish Sea ecosystem recovery—from forage fish to birds to our threatened orca whales.

Already, the Salish Sea Marine Survival Project has made a significant contribution to our understanding of salmon and is informing management actions focused on increasing their productivity and abundance. Managers around the region are drawing from SSMSP findings to prioritize estuary habitat restoration, test for pollution, and support forage fish populations. LLTK is working with partners to get solutions in the water addressing known problems identified through the SSMSP, including piloting techniques to discourage seals at predation hot spots, and a coordinated effort to improve fish passage at the Hood Canal Bridge. In addition, the SSMSP’s findings are shaping strategic policy and funding decisions in salmon recovery. Over 20% of the recommendations of the Washington State Governor’s Southern Resident Orca Task Force were influenced by the SSMSP. Further, a significant portion of NOAA’s Puget Sound Steelhead Recovery Plan focuses on actions to improve early marine survival in Puget Sound.

The Salish Sea Marine Survival Project has also stimulated interest in communication among salmon and ocean ecology researchers across the region. Around the Salish Sea, monitoring programs continue to collect and share data on ocean conditions that drive crucial food web dynamics, especially as climate change alters their patterns. We’re facilitating ongoing conversations among the partner organizations who have contributed to this research. The broad SSMSP coalition proved that ecosystem-based science and monitoring offer huge potential in improving our understanding of salmon and the marine environment. We hope to see resources to permanently support these critical research partnerships moving forward.

For detailed information about the Salish Sea Marine Survival Project, visit Read the Summary of Findings here.

Project Impact

60 +


90 +


200 +

field scientists



Project Partners

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Project Contact

Liz Duffy

Associate Director of Science (she/her)