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Fish Passage - Why are we fixing barriers?

A single removed barrier can deliver impressive benefits, improving fish access for miles both upstream and downstream. When rivers and streams are connected, fish can better access the habitat they need. This is an important component of protecting and restoring fish populations, which can in turn have multiple benefits - including for commercial and recreational fishing industries.

Why does WSDOT have barrier culverts?
Most of the culverts were installed decades before scientists fully understood the needs of fish. WSDOT met all requirements for culvert installation and sizing at the time they were constructed. Also, a culvert that was fish passable at the time of installation might have become a barrier over time due to changes in the landscape resulting from development, logging and fire. The new fish-friendly structures WSDOT constructs now are much larger and should be more resilient to changes in the landscape and provide for fish passage long into the future.

Before Photo          After Photo
 Before: Lake Creek  After: Lake Creek
SR 9 culvert that blocked fish passage
at Lake Creek, a tributary of Big Lake
near Mount Vernon.
SR 9 bridge after the old culvert was
replaced in 2015, restoring access to over
6 miles of upstream habitat for coho salmon,
steelhead, searun cutthroat, resident, and bull trout.

Number of Fish Barriers

  • Approximately 1,989 culverts are barriers to fish passage on the statewide highway system.
  • Of that total, about 1,530 are fish passage barriers that have more than 200 meters of upstream habitat.
  • As of 2016, WSDOT completed 301 fish passage projects statewide and improved access to about 1,000 miles of potential habitat upstream.

How do we know it’s working?
Biologists monitor many of our fish passage barrier corrections to ensure they’re functioning to provide fish passage. In many cases, fish are detected upstream of projects immediately after construction. See our latest Fish Passage Annual Report.