Health Check at Stillman Creek Riparian Preserve

Suited up in waders and a brightly colored personal flotation device, Washington Department of Fish and Wildlife (WDFW) habitat biologist Daron Williams uses a kick net to collect samples from Stillman Creek.

As Daron pours the creek water into several smaller trays for sorting, he is thrilled to see many small critters zipping around. “These critters are called aquatic macroinvertebrates,” he explains.

Daron is leading a group of fifteen excited volunteers on a quest to assess the health of a section of Stillman Creek in Lewis County. Healthy waterways are crucial for sustaining wildlife populations. At Stillman Creek Riparian Preserve, 6,800 feet of shoreline are protected for salmon habitat by Capitol Land Trust (CLT).

CLT conserved the property in 2020 and partnered with WDFW and Lewis Conservation District (LCD) to improve both the instream conditions as well as the stream side habitat, called riparian habitat.

This particular portion of the creek underwent major habitat restoration to improve habitat for salmon throughout their lifecycle.

But what constitutes an environment healthy enough to support young salmon? That’s what LCD and WDFW are here to find out.

“Aquatic macroinvertebrates are animals that live underwater that are big enough to see without a microscope and don’t have a backbone,” Daron continues. “While there are many types of macroinvertebrates, we are particularly interested in finding species like mayflies, caddisflies, and stoneflies. Not only are they an important food source for salmon, but their presence can also indicate good water quality because of their sensitivity to pollution.”

After all the samples are put into trays, enthusiastic volunteers use a dichotomous key and magnifying glasses to sort the samples and organize the critters by type. It doesn’t take long before a collection of juvenile mayflies, caddisflies, and stoneflies are grouped.

Macroinvertebrates like these form the foundation of aquatic food webs and are an important link in moving nutrients through ecosystems. For instance, an herbivorous mayfly eats plant material and then is eaten by a predacious stonefly. That stonefly is eaten by a salmon who is then eaten by an osprey. In this way, macroinvertebrates transform the energy of plants into forms of energy that can be consumed by other animals.

Healthy aquatic habitat requires plenty of organic material from fallen trees, branches, and leaves. So, during restoration several large woody structures and 40,000 native plants were added.

Large woody structures help feed the aquatic food chain from the bottom up. Wood provides a surface for algae to grow and often traps smaller sticks, leaves, and other organic material—all of which are food sources for a variety of aquatic macroinvertebrates. Aquatic macroinvertebrates are an important element of fish diets, and by improving the habitat for aquatic macroinvertebrates, streams can support more diverse fish populations.

In addition, as water flows around the large wood, pools and undercut banks are created that provide additional shelter and resting areas for fish. Finer sediments are often deposited upstream of a large piece of wood as the water slows, creating important spawning habitat for salmon.

Healthy riparian habitat is also crucial for macroinvertebrates, and thus fish habitat. Streamside vegetation lowers the water temperature and adds nutrients that support animal life.

“Deciduous trees, like alder, are an important element along streams,” Daron explains. “Their falling leaves provide the stream with nutrients where certain macroinvertebrates breakdown the leaf litter and make the nutrients available to animals higher up the food chain, like salmon.”

For the organizations and volunteers represented here today, the health of this important waterway is a validating discovery. It proves that the conservation and restoration work at this 38-acre Stillman Creek Riparian Preserve will ensure that aquatic macroinvertebrates and their food web will thrive here well into the future.