Research Activities


The core research program took place between 2014 and 2019. Over 200 scientists and technicians from federal, state, tribal, academic, and nonprofit institutions worked in the field and in laboratories, assessing the condition of juvenile Chinook, coho and steelhead and their marine environment. While there was overlap, the studies were grouped as follows:

Bottom-up processes: what drives food availability for salmon?

Bottom-up ecological processes—including weather, water, and plankton—are the cornerstone of the marine ecosystem, shaping whether juvenile salmon and steelhead have enough of the right kinds of prey to fuel their growth and survival. To understand these processes, researchers conducted sampling studies on both outmigrating salmon and steelhead and on plankton and marine conditions across the Salish Sea. Individual studies built on this sampling program to further hone our understanding of the relationship between salmon and their prey, and to begin identifying environmental factors driving prey availability, such as temperature, habitat availability, ocean acidification, runoff, and wastewater. Findings underscore that having the right food available at the right time is indeed crucial for early marine survival, and that climate change and habitat loss are putting salmon food supplies at risk.

Top-down processes: what are the direct threats to salmon?

Top-down effects might kill or weaken a juvenile salmon before it reaches the ocean: predators, competition for scarce resources, disease, and toxins. The SSMSP studied numerous potential factors that may contribute to salmon mortality, including predation (what eats salmon and steelhead) along with disease, toxic chemicals, harmful algae, and aquaculture impacts. Predator impacts, stemming largely from growth in the number of harbor seals in the Salish Sea, emerged from these studies as the most significant top-down cause of salmon and steelhead mortality, while disease and contaminants are also impacting some populations.

Trends and modeling

The Salish Sea ecosystem is a deeply interwoven web of causes and effects: no single factor affects salmon and steelhead survival in isolation. The SSMSP brings together new and existing data to analyze and model relationships between salmon and their ecosystem, to evaluate the cumulative effects of multiple factors, and to identify patterns and hone in on factors ultimately driving survival over time. Survival trends, ecosystem indicators development, correlative analyses, and ecosystem modeling are components of these analyses. Completed assessments reinforce connections between winds, light, temperature and food availability as well as the complex interactions that can lead to more or less predation on our juvenile salmon and steelhead. Further, the ongoing construction of comprehensive ecosystem models grounded in the data of the Marine Survival Project will help inform management decisions and prioritize recovery actions for years to come.