Wetland Recovery and Salmon Population Resilience

Tillamook has been an epicenter of salmon habitat restoration efforts over the last two years. In fact, we are currently hosting the largest wetland-restoration project in Oregon’s history. Tillamook County’s Southern Flow Corridor Landowner Preferred Alternative project–usually referred to as “Southern Flow” for the sake of brevity–is reconnecting 520 acres of tidal wetlands in the Wilson-Trask Delta. The summer of 2015 saw The Nature Conservancy’s reconnection of Stasek Slough to the Kilchis River, and the excavation of miles of tidal channels, nearly doubling the available wetland habitat in the Kilchis Delta. And going back a few years earlier, the Miami Wetlands project restored tidal wetlands at the mouth of the Miami River. Collectively, these projects add up to over 650 acres of restored habitat for juvenile salmon, and they represent a major pendulum swing in local land use, from dairy farming to the natural production of salmon.

southern-flow
This photo shows the 520-acre area being reconnected through the Southern Flow Corridor project in the Wilson-Trask delta. By 2017 this area will be available to juvenile salmon.

In the Tillamook, roughly 85% of tidal wetlands were reclaimed as farmland from the late 1800s through the 1970s. That meant the clearing of Sitka spruce forests and swamps and the diking of large areas to prevent tidal influence and saltwater intrusion. With the dikes came tidegates which were designed to allow water to flow off the land, but to prevent water from flowing in. This massive loss of juvenile rearing habitat is now recognized as one of the  primary limiting factors for Tillamook’s coho and Chinook salmon populations, which today are roughly 10% to 30%  of their historic abundance, depending on the species.

big-chinook-fingerling
Young Chinook salmon like these rely on tidal wetlands to grow big and strong.

With so many major restoration projects rolling out in the Tillamook, the big question is How will the fish respond? For the answer to that question, we’ll have to be patient, but we do have a very good case study just two watersheds to the south which points to a hopeful outcome. The Salmon River estuary, just north of Lincoln City, was the scene of intensive restoration of wetlands from 1978 to 2011, resulting in over 400 acres of reconnected salmon habitat. NOAA scientist Daniel Bottom, along with a team of fisheries scientists, studied the response of coho and Chinook salmon populations during the same period. They also looked at how the wetlands performed as rearing habitat for young salmon and how the fish used the habitat. Bottom and his team found that the diversity of coho and Chinook life-history strategies expanded dramatically with the increased rearing opportunity. And they estimated an increase of 20% to 40% of returning adult salmon as a result of the restored habitats. It was the first local study to quantify the benefits of wetland restoration to salmon, and to clearly demonstrate the connection between wetlands habitats and life-history diversity. In the years since the Salmon River studies, Bottom and others have gone on to suggest that life-history diversity among salmon is likely the key to survival in a changing world. And since wetland restoration has been shown to restore that diversity, it follows that wetland restoration is critical to the adaptation and survival of salmon populations as climate changes and sea levels rise.

Join the Tillamook Bay Watershed Council the evening of October 25th for a special presentation by Daniel Bottom. He will share experiences and revelations from his time on the Salmon River, and he will discuss the potential gains from our local restoration efforts. Don’t miss this rare chance to learn some of the latest findings in fisheries science from one of our area’s leading researchers. The presentation will be held in the Hatfield Room at the Tillamook County Library from 6:30PM to 7:30PM. We hope to see you there!

If you missed Dan’s presentation you can still see his slide here: Salmon River Study

dan-bottom-cropped
Daniel Bottom, NOAA Researcher and presenter on October 25th, 2016 at the Tillamook County Library, 6:30PM to 7:30PM.

 

 

 

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