Intern Spotlight: Students Develop Model to Focus Salmon Restoration Funds Where They Will Make the Greatest Difference for Killer Whales

Prey scarcity is one of the main threats to the survival and recovery of Southern Resident killer whales. Their preferred prey, Chinook salmon, are threatened by habitat degradation. Restoring riparian habitats that provide refuge for juvenile salmon on their way to the ocean is crucial for boosting salmon populations and providing more prey for the whales.

For my master's capstone project, I analyzed the cost-effectiveness of habitat restoration methods to support Chinook salmon recovery. My team analyzed the Stillaguamish River Basin in Washington, where Chinook salmon populations have fallen below historical abundances. Our goal was to identify which habitat restoration methods would boost the Chinook salmon population for the lowest cost per spawning adult salmon. Increasing the number of adults reproducing in freshwater habitats will help to rebuild the Stillaguamish Chinook population, enhancing prey availability for Southern Residents.

NOAA Fisheries received funding from recent infrastructure legislation to promote salmon restoration. Our project will help NOAA Fisheries focus the funding on projects with the best bang for the buck to help both imperiled salmon and the endangered killer whales.

We used the Habitat Assessment and Restoration Planning model, developed by the NOAA Fisheries Northwest Fisheries Science Center, to estimate how many spawning adult Chinook salmon each restoration method could produce. Our analysis examined three main restoration methods:

• Floodplain restoration: returning the area surrounding a river to a state that permits natural water flow, supporting the diverse habitats salmon need throughout their life stages
• Riparian planting: adding trees along riverbanks to increase stream shade, helping lower water temperatures for spawning adults and their eggs
• Installation of engineered log jams: adding woody debris in rivers to create slower-flowing regions where juvenile salmon can mature before migrating to the ocean

We then compared the number of spawners to the restoration costs for each method. The costs included construction, design, permitting, basic monitoring for 2 years, and routine maintenance for 2 years. It also included typical project management expenses. The goal was returning the site to its pre-disturbance condition.

Our results showed that floodplain restoration consistently produced the most Chinook spawners for the lowest cost in the Stillaguamish Basin. While riparian planting and engineered log jams offer some immediate benefits, they target specific aspects of habitat degradation. Floodplain restoration is more cost effective-it simultaneously addresses several root causes of declining salmon populations, such as lack of shade and availability of slow-water juvenile rearing habitat. Although our findings present the cost in dollars per spawner, this calculation only reflects the number of spawners each action could produce in the first year after restoration. As a result, the reported cost per salmon is higher than the long-term cost. These restoration actions will continue to support more spawners each year, spreading the cost across a growing number of salmon. These findings will help restoration managers choose projects that can make the most of funding to support the recovery of both Chinook salmon and Southern Resident killer whales.

This project was particularly rewarding to me as it closely aligned with my work as a Pathways Intern, where I have focused on the link between Southern Residents and their prey. Working with experts who advocate for floodplain restoration and seeing how our research supports their recommendations was enlightening. This experience has deepened my understanding of the ecological and social challenges in species recovery and has equipped me with valuable coding and communication skills. I look forward to applying these skills as I move forward with my career and continue working towards species conservation and recovery.

Meghan Roberts graduated from the Bren School of Environmental Science and Management at the University of California Santa Barbara in June 2024 with a master's degree in Environmental Science and Management. The centerpiece of her master's research was a group project prioritizing Chinook habitat restoration areas and strategies to increase Chinook salmon populations, a key prey species for endangered Southern Resident killer whales. Her team included fellow master's students from the Bren School: Raymond (Ray) Hunter, Lars Nelson, and Logan Ruggles. Starting in July 2023, Meghan interned with the Protected Resources Division of NOAA Fisheries' West Coast Region under the NOAA Pathways Internship Program. Meghan will continue her Pathways internship through September 2024.

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