This past year, BIWC partnered with Wild Fish Conservancy (WFC), a PNW-based organization that conducts research and action to restore wild fish populations, to conduct baseline sampling for Mac’s Dam Creek to evaluate whether fish are present in this stream system. The inspiration for this work is a planned removal of a historic check-dam about half way up the stream system that presents an impassable barrier to fish. This barrier is one of the most severe – but not the only obstacle- to fish in this watershed, and the City is planning to work with IslandWood to remove this dam in 2027.
BIWC and WFC received a grant from the Bainbridge Community Foundation to conduct environmental DNA analysis on Mac’s Dam Creek, a stream that flows through the IslandWood campus before entering Blakely Harbor on the east side of Bainbridge Island. Environmental DNA, or eDNA, analysis uses a method that filters the water column to collect fragments of DNA that are shed by organisms in the watershed. eDNA is increasingly a widely used tool to sample for the presence of organisms that might be difficult to visually observe, and a growing number of laboratories support this type of sampling with test kits and analyses that can detect a diversity of fish and wildlife. We conducted three sampling events over fall 2025- spring 2026 in order to capture samples from periods of time that we expected fish to be present in the system both below and above known fish passage obstacles and barriers.
We found no eDNA evidence of fish in the Mac’s Dam Creek system above any of the stream barriers. This baseline data will be important when the City begins to remove the barriers along this stream system; we hope to repeat these analyses following removal to understand whether, as we hope and expect, fish move back into this system. Data like this is a key component of establishing evidence of absence- rather than moving forward with an absence of evidence! This work can help us better understand the value of efforts to remove in-stream barriers and how these efforts contribute to fish population health.
Read more about this project in Wild Fish Conservancy’s eDNA Project Report for Mac’s Dam Creek.