Stillaguamish Tribe monitors fish use before and after dike removal

The Stillaguamish Tribe’s natural resources department is monitoring fish use of the Port Susan estuary before and after a 150-acre restoration project.

The tribe was contracted by The Nature Conservancy, which is removing a dike built years ago to create farmland near the mouth of the Stillaguamish River. With the dike removed, the tide will be free to inundate the estuary, giving juvenile salmon access to better rearing habitat, and alleviating a community flood threat.

“When the lower Stillaguamish River floods, it tends to overtop levees upriver and back up inside the dike like a bathtub with no outlet, until enough pressure builds to carve holes in the levee,” said Kat Morgan, Port Susan Bay program manager for the conservancy. “This causes expensive damage to the infrastructure and farm fields. Everything that is caught up in the flood water, including fish, ends up stranded as the water slowly recedes.”

As part of the restoration, a series of tide gates will be installed next to Hatt Slough to act as a relief valve during floods.

The loss of estuarine habitat may be a significant limiting factor in salmon recovery.

“We’ve invested a lot in the recovery of Stillaguamish chinook,” said Shawn Yanity, Stillaguamish tribal chairman. “As co-manager of the fisheries resource, we hope this project will help us make progress toward our goals in the Stillaguamish Chinook Recovery Plan.”

Removing the dike will allow new channels to develop. “Blind tidal channels have been greatly reduced in Port Susan,” said Jennifer Sevigny, biologist for the tribe.

Sevigny and fisheries technicians Kevin Graybill and Jody Pope began beach seining in Port Susan in April 2011, a year before the restoration work began. The initial monitoring provides baseline data that can be used as a reference point for tracking changes after the dike is gone. Future sampling will show how salmon take advantage of the new habitat.

The Nature Conservancy owns the 4,122-acre Port Susan Bay Preserve, which encompasses most of the Stillaguamish River estuary.

For more information, contact: Jennifer Sevigny, biologist, Stillaguamish Tribe, 360-631-2372 or [email protected]; Kari Neumeyer, information officer, NWIFC, 360-424-8226 or [email protected].