Key Hypotheses

What do we think is going on?

We appreciate the complexity of ecosystems: how multiple factors may be interacting and contributing to the fate of juvenile salmon and steelhead in the Salish Sea. To address this, we convened scientists from U.S. and Canada to develop a comprehensive, multi-disciplinary, and highly coordinated research program at an ecologically relevant scale – the entire Salish Sea.

The scientists concluded the key hypotheses are, in order:

  1. Bottom-up processes—including weather, water, and plankton—that drive juvenile Chinook, coho and forage fish prey availability have changed, and salmon aren’t able to compensate. This is limiting salmon growth and survival.
  2. Top-down processes have also changed. Primarily, there are more predators eating steelhead, resident salmon and larger forage fish.
  3. Additional factors are exacerbating these ecological shifts, including toxics, disease, competition, and the cumulative effect of significant top-down and bottom-up shifts occurring simultaneously.

Click here for a comprehensive list of hypotheses and their assessment status