Salmon at Night: Lake Washington
Research Update: March 2026
Thank you to those of you who participated in the lights on/lights off study this month! The Cedar River hatchery has already released several million baby sockeye salmon in 2026, and we have seen some of these tiny salmon along the shoreline at night with our acoustic camera. We expect to see more fish in the next months as the water warms and fish grow.
Who We’ve Seen
In our overnight nets, we caught yellow perch and two hybrid coastal cutthroat/rainbow trout. All had either non-biting flies and other bugs in their stomachs or had empty stomachs. Fish caught near the mouth of the Cedar River also had bugs and plankton for diets.
We plan to return to your shorelines on back-to-back nights in April, May, and June, as close to the new moon as possible.
Upcoming Tentative Testing Dates:
We will check in a week before to let you know when we’ll be on the water. As the lake levels rise from snow melt, we expect young salmon to begin using the extra shallow habitats along your shorelines--small beaches, ramps, and steps--for refuge at night.
Check out our Instagram @uw_wetlandecosystemteam for periodic updates on this and other projects we are working on.
See you in April!
Kerry Accola
Video Above: Acoustic camera footage of juvenile salmon navigating the shoreline at night
Video Above: USGS Team dropping gill nets in the research area.
Salmon Habitat in Lakes
South Lake Washington shorelines are crucial habitat for young salmon as they leave the Cedar River. Along these shorelines, they eat and grow and seek refuge from predation before they leave for the Ballard Locks and ocean life.
Shallow habitats provide safety from predators for salmon. Shoreline habitats also frequently have high levels of shoreline lighting at night, known to attract salmon and other fish.
We Need Your Help!
A select number of homeowners (5 houses) can help!
Your shoreline has been chosen because these shorelines have high densities of salmon at night, and extra shallow habitats that salmon prefer to rest and take refuge in at night.
For one night per month, from February to May (4 nights total) 2026, we ask for participation in a meaningful contribution; modifying your outdoor lighting. On the designated night, we ask that you and your neighbors turn your dock and yard lights off, and on another night that month, we will ask you to please keep them on as usual.
During February – May 2026, UW and USGS scientists will be setting nets offshore to study predator fish populations. Scientists will set nets at night and pick them up in the morning, trapping yellow perch and other potential salmon predators. The net holes will be large enough that salmon can swim through—they will not be captured. Scientists will study yellow perch stomach contents to see if they eat salmon during the night, or if they rest, as both perch and salmon avoid larger predators in deeper waters.
We hope to better understand if, when, and where young salmon are eaten at night. This work will help contribute to salmon recovery by prioritizing key components to their early survival.
What We’ll Be Doing:
Night Lighting & Shallow Habitats:
How Do They Interact?
In 2024, UW scientists snorkeled along South Lake Washington shorelines day and night (February-April) to study young salmon as they left the Cedar River.
Salmon and other fish, especially non-native yellow perch, were uncommon along shorelines during the day but were common at night in large numbers, when the fish came to shore to rest for the night.
Salmon are known to be attracted to lighting at night, but the salmon were most common along residential shorelines (yours!) rather than at locations with the highest lighting (Boeing, Hyatt hotel), meaning they are more attracted to shallow habitats than to light, likely trying to stay safe from predation.
During studies of juvenile salmon, researchers found that 30% of young Chinook counted during the study were found in extra shallow (1 ft) residential habitats (pocket beaches or concrete ramps), even though these shallow habitats were less common.
Using this new information, researchers want to study if smaller predators like yellow perch use light to hunt at night, or if all fish rest together from larger predators. So, they are returning in 2026 to the shallows of Lake Washington!
Plot showing night locations of salmon in S. Lake Washington. Most salmon were along residential shorelines with yard and dock lights; next, Gene Coulon Park. Few salmon were at Boeing or Hyatt hotel, which have high light at night.
What More Can We See?
UW scientists hope to set an acoustic camera at an extra shallow habitat to see how many salmon use the habitats, and how salmon and yellow perch interact at night.
An acoustic camera takes images using sound and turns them into digital images - think of these as a snapshot in time. To the right is an acoustic image of a school of ~250 young chum salmon. Images are captured 2-7 m in front of the camera. We will be able to ‘see’ what happens at night without disturbing the fish.
We would greatly appreciate your participation in this study. Please contact us with any questions!
Kerry Accola | University of Washington | kaccola@uw.edu