Elwha River Weir Summary 2011

The Elwha River weir (a temporary trap) was re-installed on August 18, 2011, to count and collect biological data from adult salmon and steelhead as part of an ongoing effort to determine how these populations change as a result of dam removal. A secondary goal is to provide broodstock for hatchery production and conservation during dam removal when turbidity levels are expected to be lethal to fish in the river.


2.340 cfs and still working

Due to an unusually high snowpack (190% of normal), the trap had to be installed at a flow of 1,640 cubic feet per second (cfs). The first fish caught was a sockeye, which was marked and passed upstream. The trap fished continuously from August 18 to October 19, 2011, except for three days when flows exceeded 4,000 cfs. The weir was once again pushed to the limits in 2011, fishing at flows over 2,500 cfs (compared to a high of 2,200 cfs in 2010), which significantly exceeded our weir design expectation of 2,000 cfs. The weir was removed on October 19, 2011, after the removal of a log boom at the Elwha Dam which resulted in the release of hundreds of large logs into the lower Elwha River.

A total of 647 live and dead (carcasses) salmon and trout were captured at the weir during the 2011 summer/fall season, compared to 492 fish captured in 2010. A total of 218 live adult salmon and trout, representing seven different species including Chinook (73), pink (129), chum (1), coho (1), and sockeye salmon (8), and steelhead (3) and bull trout (3) were captured at the weir in 2011.  


Species present in the Elwha River

Fifty-five Chinook salmon were retained for the Washington Department of Fish and Wildlife Chinook salmon broodstock program at the Elwha rearing channel. One hundred twelve pink salmon were also retained as broodstock for the pink salmon captive brood program. This program is designed to protect the pink salmon stock during lethal turbidity levels occurring during dam removal.

In addition to the live fish caught at the weir, 429 salmon carcasses, including 381 Chinook and 48 pinks, were handled. These post-spawn carcasses represent fish that had either migrated upstream past the weir before it was installed or were passed above the weir by weir personnel.

Data collected for fish caught at the weir included, species, fish condition, sex, origin (wild/hatchery), presence/absence of coded-wire tags and passive integrated transponder tags (PIT), fin condition, length, scale samples for aging, DNA samples, and information on adult run timing. Otolith samples were collected from Chinook salmon carcasses.



Sampling a sockeye salmon for PIT tag detection

The weir is planned to be re-installed during the winter of 2012 to capture and count adult steelhead and any other adult salmonids migrating in the Elwha River. In addition to biological data collection, the weir will be used in conjunction with a SONAR system to assess steelhead abundance.

The Elwha River weir project is part of a multi-agency effort which includes the Lower Elwha Klallam Tribe, National Oceanic and Atmospheric Administration (NOAA), Olympic National Park, U.S. Fish and Wildlife Service, U.S. Geological Survey, and Washington Department of Fish and Wildlife (WDFW), to evaluate the response of adult salmonids to the removal of two Elwha River hydroelectric dams. The weir was funded in 2011 by cooperating agencies as part of their annual budget. Additional funds were obtained through the President’s stimulus program (American Recovery and Reinvestment Act) which funded the project through September 30, 2011. The weir is funded through September 30, 2012, with funds provided by USEPA through the Puget Sound Partnership.