In the Field: Crayfish Sampling - Columbia Land Trust
Join our staff as they sample stream beds for crayfish and mussels in the headwaters of the Washougal River

They’re not always top of mind when we think about wildlife, but invertebrates often have much to tell us about the condition of the lands and waters they call home.

On a warm July evening, Columbia Land Trust intern Gabe León arrived at the Wildboy Creek conservation area to install crayfish traps. Just before sunset, he packed his backpack and bushwhacked his way to the shallow water near the Kwoneesum reservoir in the upper reaches of the Washougal River system. Once León arrived at his surveying spot, he carefully prepared the traps by putting a small amount of dry cat food—yes, cat food—inside and then set the traps into the water to be checked in the morning.

There are very few species of crayfish native to Pacific Northwest. In fact, the signal crayfish (Pacifastacus leniusculus) is the only crayfish native to the Washougal River area. There are several species of non-native crayfish, such as the rusty crayfish, that are detrimental to the health of the native fish and stream ecology.

In addition, there are several native species of freshwater mussels in the area, and very little is known about their distribution and status in Southwest Washington. Freshwater mussels are extremely important for water quality in our streams and they are dependent on our native salmonids for reproduction. Their presence is often an indicator of river system health.

The next morning, León and fellow Land Trust intern Helen Gavrilov headed back to check out if the cat food baits worked. They put on their waders and trekked through the thick brush on the steep banks of the reservoir. They waded through the water and began turning over rocks while using aquascopes (underwater viewers made of plastic tubes) and waterproof flashlights for clearer and brighter viewing.

“One of the goals [of the sampling] is to develop a community science program to directly engage people in conservation work,” said Gavrilov. “We started testing the survey protocols at Wildboy Creek and plan to expand to other locations on our conserved lands.”

Gavrilov is interning with the Land Trust this summer as part of her studies in fisheries and wildlife science while also serving on staff as our administrative assistant.

“The pace moves slow and careful,” said Gavrilov. “We don’t want to step on any mussels or frighten the crayfish before we get a good look at them.”

For the Land Trust, it is important to be aware of the crayfish, mussels, and other freshwater organisms that are present in nearby streams as we form plans and continue restoration projects. It is particularly important at the newly conserved Wildboy Creek, as we intend to remove the Kwoneesum Dam in the coming years. Information collected prior to dam removal will help project managers more fully understand how the plans could impact the native species.

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“Freshwater mussels can’t move out of harm’s way,” said Gavrilov. “The data we gather through the mussel surveys on other conserved lands will help us learn more about mussel distribution throughout our service area, both for project planning and for long-term monitoring as climate and stream conditions change.”

The team was successful in observing crayfish inside the traps. They found a large population of signal crayfish of different color variations in the streams near Wildboy Creek. They also found some western pearlshell mussels in Wildboy Creek just below the dam. No mussels were found above the dam and no invasive species of crayfish, mussels, or clams where found in the sampling.

The crayfish surveys further provide a monitoring network to detect the presence of any existing or new invasions of species of crayfish that could harm the ecosystem. For example, the rusty crayfish, which has been introduced in the John Day River, is now spreading to the Columbia River. There is great and growing concern about the ecological changes and impacts this species will have on our river systems, and on salmon in particular. Rusty crayfish can overrun salmon redds (spawning grounds) and devour eggs.

“We are still in the beginning stages of developing this program,” said Gavrilov. “Gabe has done a lot of research on crayfish and freshwater mussels in our area and compiled background information for the protocols that will give future volunteers valuable context for this work and guidance on how to identify different species of crayfish and mussels.” León set up these research protocols this summer as part of an internship through the Doris Duke Conservation Scholars program.

As we move forward with removing Kwoneesum Dam in partnership with the Cowlitz Indian Tribe, and with managing and restoring other rivers and streams, we’ll continue to observe freshwater invertebrates and measure if and how our actions impact them as well as the greater health of their habitat.

We at the Land Trust are grateful to interns Gabe and Helen for conducting research while adapting to changes in summer plans due to the COVID-19 pandemic. We also want to thank the Xerces Society for partnering with us to develop this conservation program. We look forward to when we’re able to host community science events on the land again.