CREATING A HEALTHY WATERSHED
It's a cold and windy Wednesday morning near the mouth of Tryon Creek. A few hundred yards upstream, above the culvert running below Highway 43 at the dividing line between Portland and Lake Oswego, thousands of drivers speed past without much thought of what's going on down below.
That's typical for small, urban streams like Tryon Creek. It's easy for city dwellers to overlook the trickling waterways that contribute to the larger rivers and lakes that define the greater landscape.
But down at the mouth of the creek, the U.S. Fish and Wildlife Service is collecting important data that has widespread implications for both the wild habitat of these streams and the urban infrastructure that surrounds them. It's here that federal officials are working with the City of Portland on a plan to replace a concrete box culvert that was built in the late 1920s, when the surrounding gully was filled in to provide a level surface for the roadway above.
The culvert allows the creek to flow under Highway 43 to reach the Willamette River, but its narrow size and flat base cause the water to flow too fast for some wildlife to pass through. As a result, several endangered and threatened species of salmon and other fish have mostly been cut off from upper Tryon Creek, which used to be part of their natural habitat.
The proposed replacement culvert would be a 400-foot-long, 30-foot-wide and 12-foot-high arch, which would be significantly larger than its predecessor. The "floor" of the structure would be made up of rocks and natural creek bed materials, creating a less-uniform flow and making it easier for fish to swim against the current.
Kaitlin Lovell, manager of the Science Integration Division in the City of Portland's Bureau of Environmental Services, is working with the USFWS to learn about watershed health and fish populations in areas like Tryon Creek. She says the City will use the information now being collected to guide the culvert project, pending congressional approval for funding to allow the U.S. Army Corps of Engineers to begin work on a final design.
The goal, Lovell says, is to better allow the free passage of coastal cutthroat trout and other fish through the culvert by making sure young fish have slow-moving pockets and rest spots to ensure safe passage.
"Fish are knocking at the door of that culvert," Lovell said. "As soon as we open it, they will be making their way up the culvert, and this data tells us which species and where in their life stage these fish are that are using this habitat."
On this outing, Brook Silver and Brian Davis of the Columbia River Fish and Wildlife Conservation Office are electrofishing in Tryon Creek. It's a process that allows the fish biologists to stun juvenile fish hiding in the creek so they can easily capture, identify, measure and release them without causing any harm.
Silver makes her way up the stream toward the culvert, using a large wand-like rod with a sort of lasso attached to it that emits an electric shock. On her back and connected to the rod is a pack that carries an electric charge. The pack is a bit clunky and looks like something out of a "Ghostbusters" film.
Directly behind her, Davis holds a net, ready to catch any fish that Silver stuns so they can be placed in a bucket full of water. It's a slow process, but after about 30 minutes, the pair of biologists have caught four fish — three salmonids and one tiny reticulated sculpin.
Their mission is to find coastal cutthroat trout, a specific species that they located in upper sections of Tryon Creek in 2017. Silver and his USFWS colleagues have been studying the status, abundance, distribution and habitat preferences of the species in the creek, suggesting in a report published in October that an urban stream can support a healthy fish population.
The coastal cutthroat trout they found last year exhibited characteristics similar to fish populations not influenced by urbanization in forested areas, the report said. The Tryon Creek population was genetically diverse, varied in size and free of pathogens, and the fish exhibited typical migratory behavior.
Silver and Davis are able to observe the migratory behavior of cutthroat trout by tagging juvenile fish with passive integrated responders, or "PIT tags"— tiny electronic devices that can be coded with one of 35 billion unique codes.
A series of gates that can read when a tagged fish passes through have been set up at the mouth of Tryon Creek where it meets the Willamette River. By using multiple gates, the biologists are able to tell not only whether a tagged fish has passed through the gates, but also if it is swimming upstream or toward the Willamette.
"I think the detection of fish coming and going from Tryon Creek shows this habitat is connected, and that these fish do have the ability to exit and return," Silver said. "These off-channel habitats are used as a refuge for juvenile fish heading to the ocean."
While they didn't find any coastal cutthroat trout on this outing, Silver and Davis were able to catch two Chinook salmon and one Coho — a great consolation, considering the Coho salmon is listed as "threatened" federally and "endangered" in Oregon.
The Coho's presence in Tryon Creek is a good indicator that improvements already made to this particular stretch of Tryon Creek by the City of Portland have positively impacted the habitat, Silver said, and she believes the fact that these fish are present shows that the culvert is in fact used by fish to gain access to other parts of Tryon Creek upstream.
For that reason, the Tryon Creek Watershed Council, the City of Portland, the City of Lake Oswego and the Oregon Department of Transportation have put together a thick stack of letters urging Oregon Senators Ron Wyden and Jeff Merkley to push for the culvert project to be included in Congress's omnibus budget bill later this year.
Any extra support from individual citizens would be a huge benefit for the project's future, Lovell said.
For Silver, tromping around Tryon Creek, tagging fish and taking other measurements is all in a day's work, but she says that the real task is using the information she gathers to improve the watershed for the continued preservation of all the fish that make their home in the trickling waterways that lead to rivers and lakes.
"It takes work to preserve and maintain large connected spaces like Tryon Creek," Silver said. "If we want to protect sensitive species in urban habitats, it is essential that we promote these urban spaces and engage the community. By increasing preservation and promoting stewardship, we can positively affect not just the cutthroat trout in Tryon Creek, but everything else that lives downstream."
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