The Port Gamble S’Klallam Tribe is tracking juvenile salmon that are using an unlikely place to find refuge—a shipping canal.
The tribe has been keeping an eye on a growing bull kelp bed as potential salmon habitat in the Port Townsend Shipping Canal, which is unique since most bull kelp beds in Puget Sound are in decline, said Hans Daubenberger, the tribe’s senior research scientist.
The waterway is located between the Quimper Peninsula and Indian Island, which were once connected on the south end by a sand spit at low tide. The sandspit was eventually dredged, creating the canal.
Over the years, the high water velocity in the canal supported bull kelp growth, which piqued the tribe’s interest, since fish use the canal to migrate from Puget Sound to the ocean, Daubenberger said. Since 2014, the tribe has been studying the migration patterns of coho salmon that depart from the tribe’s net pens in Port Gamble, as well as chinook coming from Puget Sound and Hood Canal.
To better understand how juvenile salmon are using the shipping channel, the tribe inserted acoustic tags into a sampling of chinook and the tribe’s hatchery coho to track their migration patterns in 2024 and 2025. The tribe has partnered with the U.S. Geological Survey Marrowstone Marine Field Station to use its facilities for tagging surgeries because of its high-end filtering system for sea water, creating a clean marine environment for the fish.
The tags make a high-frequency ping every 30 seconds, transmitting a timestamp that is picked up by acoustic arrays installed around the canal. Based on how fast sound travels through water, the tribe can triangulate the position of the fish when the receivers read the timestamp.
“We learn where they are going within that space,” Daubenberger said. “Are they moving in and out of it? Do they move right through it? What does that look like from a behavior standpoint?”
The 2024 data showed some fish stayed for two weeks in the bull kelp bed, surprising scientists who thought the fish would hang out only for a few days before moving on.
In the latest round of tagging, the tribe is inserting into some of the fish a slightly larger and more specialized tag that can pick up temperature and depth. Based on studies the tribe has been doing on juvenile salmon at the Hood Canal Bridge, scientists know that increased temperatures usually mean a fish has been eaten by a predator. By tracking depth, the tribe also learns where fish prefer to be in the water column, which is important in relation bull kelp.
“It turns out that the bull kelp in this area is developed enough for juvenile fish to be able to use it,” Daubenberger said. “Most juvenile salmon swim in the top 3 feet of the water column, so if the kelp isn’t tall enough by the time the fish get there, they’re not going to use it. But when these fish are migrating in spring and summer, this particular bull kelp bed is fairly well developed.”
The tribe also is working with the Puget Sound Restoration Fund to enhance the existing bull kelp bed to stretch the length of the canal on the west side, which is riprapped, while the east side on Indian Island still has a natural shoreline. The riprap—a wall of loose rock that acts as a breakwater—was installed along the shoreline to maintain flow through the channel and prevent it from filling back in. But shoreline hardening destroys habitat for juvenile fish that need places to find refuge and feed as they migrate to the ocean.
“The idea is to improve passage of juvenile fish through a channel we know they use to get into Port Townsend Bay,” Daubenberger said. “There’s a lot of nearshore habitat in Port Townsend Bay that’s very beneficial to fish migration.”
A juvenile chinook is measured for length at the USGS Marrowstone Field Station before an acoustic tag is inserted into its belly, to help the Port Gamble S’Klallam Tribe track its migration through the Port Townsend Shipping Channel. Story and photos: Tiffany Royal
