‘Intensively Monitored Watersheds’ Report Details Habitat Restoration Benefits For Juvenile Salmon, But Lack Of Increase In Adult Abundance
In the Pacific Northwest, thirteen watersheds are “intensively monitored” to provide key data on regional salmon and steelhead recovery efforts. A new report has mixed messages about the success of habitat restoration in boosting returns of adult fish listed under the Endangered Species Act.
The good news: Positive fish responses from habitat restoration were most commonly observed for smolt and juvenile life stages.
The bad news: There were few ‘Intensively Monitored Watersheds’ that reported an increase in abundance of returning adult fish.
“Many IMWs noted that poor marine survival and factors impacting fish outside the area where habitat treatments were applied, such as harvest, hydropower, and hatchery programs, all could limit the capacity of adult fish to respond to improvements in freshwater and estuarine habitat conditions,” says Management Implications from Pacific Northwest Intensively Monitored Watersheds.
The report from the Pacific Northwest Aquatic Monitoring Partnership urges realistic expectations when it comes to how much can be done at the watershed level to enhance returns of imperiled wild salmon and steelhead.
“The fact that some salmon populations are impacted by factors other than habitat conditions does not imply that habitat restoration is not beneficial; high-quality freshwater and estuarine habitat can support population resiliency by enhancing fish capacity to persist in the face of climate change or severe disturbance events (e.g., major floods, wildfire).
“Identifying the full suite of factors affecting salmon and steelhead should occur at project establishment and specific intervals following implementation. This process is essential for restoration and recovery programs to establish realistic expectations of fish response to habitat improvements,” says the report.
The report compiles general results to date from thirteen ‘IMWs’ across the Pacific Northwest and provides an initial indication of the management implications of these studies.
In the Columbia/Snake river basin, the monitored watersheds include the Lower Columbia, Wind River (WA), Methow River (WA), Asotin Creek (WA), Potlatch River (ID), Lemhi River (ID), Bridge Creek (OR), and Middle Fork John Day (OR). The list also includes Washington’s Skagit River Estuary, Elwha River, Hood Canal and Strait of Juan De Fuca, and Pudding Creek in California.
The most common treatment types evaluated by the IMWs are large wood addition, riparian restoration, and barrier removal. Fish species included in the evaluations include steelhead, Chinook and Coho salmon, Bull Trout, and Pacific Lamprey. Eleven of the IMWs indicated they are targeting more than one anadromous species.
Many salmon and steelhead populations in the Pacific Northwest have been assigned protection under the Endangered Species Act over the last 30 years. Hundreds of millions of dollars have been spent on the restoration of freshwater and estuarine habitat.
Yet, is the money being well spent? How do we know?
That information gap led to the establishment of IMWs in the early 2000s. An IMW is an experiment in one or more catchments with a well-developed, long-term monitoring program to determine watershed-scale fish and habitat responses to restoration actions.
“The IMW approach is considered an effective experimental design for evaluating watershed-scale salmon and steelhead responses to habitat restoration,” says the report.
IMWs also provide opportunities to better understand other aspects of salmon ecology and watershed processes: multiple studies identified a diversity of life history strategies by salmon and steelhead through the intensive, life-cycle monitoring that IMWs rely on.
And monitoring activities have also captured climate change events, like drought and fires, that restoration programs must account for moving forward.
The report highlights the need for improved methods for incorporating future IMW findings into the processes for selecting restoration projects.
The report found that habitat responses to treatments reported by the IMWs indicate that 75% showed a positive response, 2% a negative response, and 23% no change.
Fish responses reported by the IMWs included 53% identifying a positive response, 3% a negative response, and 44% no change.
Several treatment types such as removal of fish passage impediments like dams and culverts, were consistently associated with increased access to habitat and a positive fish response across IMWs. This result is consistent with previous studies done at reach or project scales.
Similarly, enhancing fish access to floodplain or tidal delta habitat by removing barriers or encouraging beaver colonization increased abundance and growth of salmon and steelhead at most IMWs where this treatment type was evaluated.
Preliminary results are less clear though for habitat and fish responses to large wood placement: some IMWs noted positive responses while others have yet to observe a response. “The need to better understand how large wood restoration may support achieving watershed and population-scale goals is recommended given how common this treatment type is in restoration programs,” says the report.
Positive fish responses were most commonly observed for smolt and juvenile life stages along with changes in distribution and life history diversity.
There were few IMWs that reported an increase in abundance of returning adult fish.
Many IMWs noted that poor marine survival and factors impacting fish outside the area where habitat treatments were applied, such as harvest, hydropower, and hatchery programs, all could limit the capacity of adult fish to respond to improvements in freshwater and estuarine habitat conditions.
One or more of these external factors affected fish at every IMW.
The report includes sort-of report cards for each watershed. For example, for the Middle Fork John Day, an undammed watershed, the report card says:
“Monitoring efforts have not yet detected a change in steelhead or Chinook Salmon productivity at the population scale compared to reference watersheds, and it will likely take several salmonid life-cycles (20-30 years) before improvements in productivity can be detected. While average redd count and spawner abundance has remained static, redd distribution has shifted downstream to restored reaches, indicating a preferential selection of restored habitat for spawning activity.”
Another example, the Lemhi River:
“Juveniles: increase in abundance and upstream expansion of Chinook Salmon, steelhead, fluvial Bull Trout, providing survival advantages of fish using reconnected tributaries. Adults: Steelhead spawning activity in 3 fully reconnected tributaries, Chinook Salmon entry into 2 fully reconnected tributaries, and steelhead entry into 1 partially reconnected tributary, but no observed spawning activity.
Top 3 Management Implications
1. Tributary reconnections in the Lemhi River basin provided additional habitat for spawning adult steelhead and for rearing juvenile Chinook Salmon and steelhead.
2. Newly created braided channels and floodplain reconnections in the Lemhi River were used immediately after implementation by adult and juvenile Chinook Salmon and steelhead.
3. Overwintering habitat for juvenile anadromous fish is limited in the Lemhi River. Increased habitat diversity will result in increased overwinter survival and Productivity.”
The report recommends the following management and policy actions:
1. Build restoration plans and strategies at watershed scales and within a context of all potential impacts to salmon and steelhead viability.
2. Prioritize restoration methods based on aspects of restoration technique effectiveness like cost and certainty of success.
3. Implement restoration actions at continuous, landscape scales.
4. Prioritize and support the development of formal adaptive management processes across recovery and restoration programs.
5. Regularly communicate among IMW monitoring and restoration leads and local stakeholders to refine habitat restoration programs based on study results and facilitate adaptive management.
6. Support and implement natural resource programs at watershed and salmon- and steelhead-species scales.
7. Provide stable, long-term support for fish and habitat monitoring.
8. Consider converting some of the IMWs to long-term research sites.
9. Provide support for restoration planning and permitting to accelerate implementation timeframes.
10. Communicate with stakeholders about their expectations of habitat restoration
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