Study: Fish use as metric for ecological function
This paper presented an overview of results to date of CWI’s ongoing study to define how nearshore ecological function responds to dam removal sediment delivery through three time phases: 1. Pre-dam removal; 2. Dam removal; 3. Post-dam removal
Sediment delivery has just begun. Numbers change daily, but somewhere between 20-60 percent of the 16 million cubic meters (what an astounding number!) of sediment predicted to be delivered to the nearshore has arrived. Physically, restoration has just begun.
While the story is still unfolding-remember dam removal is not yet complete and sediment is just starting to arrive to the nearshore-we’re seeing the following changes in the Elwha estuary. We attribute these changes with dam removal as we are not seeing these changes in the comparative Salt Creek area.
In a nutshell?
Species Richness is highly variable in the nearshore, and defined by month. Species Richness in the Elwha estuary has not changed significantly since dam removal began, and is not significantly different than that of the comparative area.
We may be seeing some response in Chinook and coho use of the Elwha estuary-hatchery releases make it VERY hard to decipher….
Observations of our chum data are very intriguing. While overall abundance appears to be about the same, when, and the size of, juvenile chum are using the Elwha estuary appears to be changing.
It is vital to stress that these results are preliminary and will undoubtedly change as the Elwha nearshore continues to restore. We will continue to work on these elements in more detail for the upcoming post dam removal phase. Our informal, preliminary observations to date:
- Overall, ecological function of the Elwha estuary is functioning at pre-dam removal level thru the dam removal phase. New estuary sites functioning at same ecological level for fish as original Elwha sites. As soon as the estuary habitat is available juvenile salmon are using it.
- Elwha nearshore estuary habitat is changing rapidly: both estuary and lower river habitat are expanding. Both changes are reflected in fish use as the estuary and lower river grow.
- Chum use of the estuary may be more complex than initially understood – juvenile appear to be leaving the estuary earlier, and smaller than prior to dam removal. We’ll assess this in more detail once dam removal is over.
- Hatchery releases currently occur at the peak of juvenile chum use of the Elwha estuary. Given the importance of the estuary for restoring chum, and the historic importance of chum to the watershed, chum should be considered in much more detail when considering adaptive managment options for the watershed. We’ll assess this in the near future after 2014 (dam removal) outmigration season and project phase is over.
Thank you to:
All provide critical habitat for the fish that are drivers for the dam removal project including Chinook, coho, chum, steelhead, bull trout, cutthroat, herring and eulachon (Shaffer et al 2008; Ward et al 2008). They simply can’t live without a functioning nearshore.
nearshore. As a result, much of the Elwha nearshore is a hostile lunar landscape because of the sediment starved beach topography and wave energy-a far cry from what it should look
and Ritchie 2013) -literally before our eyes. And what are the fish doing?
‘Defending infrastructure’ is traditionally done thru bulkheading. This involves placing large rock and or sheet pile along the shoreline, which in turn ironically causes a swift and expensive increase in erosion, and rapid unbraiding of nearshore ecosytem function. Revetments such as along the Port Angeles landfill shoreline are expensive and futile-maintenance costs for these armaments can average $2000 per feet per year (based on City of Port Angeles utility costs), and at best only slow erosion rates by half.
Comparision of unarmored Dungeness and armored Elwha feeder bluffs
of sediment starvation and fully restore our nearshore Elwha-but we have to act now. Stay tuned for details on what CWI is discovering as we work to protect and restore our nearshore ecosystem-and how you can become part of the solution.