WSF Lights the Way for Salmon

Friday, March 7, 2008


WSDOT’s Ferry Division hopes to light the way for migrating salmon in Port Townsend. A new research project is taking place at the Port Townsend Ferry Terminal that will assess how migrating fish respond to artificial light.

(at left: Two solar dishes provide not only power for the dock lights but also adjust the intensity so that the natural light is replicated under the dock.)

Studies have shown that structures like ferry docks cast shadows over the waters near shore and affect the migration of juvenile fish. Because the small fish are used to bright water, they avoid the dark areas and maneuver around the structures, driving them into deeper water where they are more likely to become prey for other fish and birds.

To counter this effect, WSDOT, along with the University of Washington and the Pacific Northwest National Laboratory, are installing a fiber-optic lighting system under the Port Townsend Ferry Terminal to encourage fish to migrate under the structure. A solar power system above the terminal will run the lights during the day in an attempt to match sun levels in open water.

(at right: Fiber optic lights may help juvenile fish continue their migration in near shore waters that are covered with docks and other structures.)

“We’ve tried metal grates and glass blocks to allow light to pass through ferry docks at other terminals with some success,” explained Rhonda Brooks, WSDOT research manager. “The hypothesis of the research is that fiber-optic lighting is even closer to natural light and will have benefits to the fish as well as eel grass, which is essential in the juvenile salmon habitat.”

The research project will last two years and will be monitored by WSDOT environmental experts. During this period, researchers will track the patterns of the migrating salmon, measure light levels under the dock and fish behavior, and look for growth of eel grass under the dock. The data being collected will help better measure the impacts of structures over water and identify ways to minimize those effects.

WSDOT’s Research Office and Ferry Division funded the $300,000 study. A final report will be developed in 2009. Visit the Research Office to learn more about other research projects taking place at WSDOT.

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