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.

     


Elwha River Weir

An adult fish trap, termed a resistance board weir, was installed in the Elwha River in September 2010 to begin counting adult salmon, trout, and char migrating upstream and downstream in the Elwha River. The weir 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 monitor the influence of removing two Elwha River hydroelectric dams on salmon and steelhead returns to the Elwha River ecosystem. The goal of the project is to count migrating adult salmon and steelhead to determine if run sizes increase in the Elwha River following dam removal. A portion of the adult salmon captured at the weir will also be used as broodstock for hatchery production and conservation.  Hatcheries will be used for Chinook salmon, coho salmon, chum salmon, pink salmon, and steelhead as a safeguard to protect Elwha River salmon runs during dam removal, which is expected to result in short-term sediment concentrations that may kill adult salmon. In addition, information will be obtained from the weir to determine when different species of adult salmon enter the river, their age, and genetic makeup.

Adult trap (resistance board weir) in the Elwha River

At 195 feet across, the Elwha weir is thought to be the largest floating weir on the WestCcoast. The weir consists of 52 floating panels connected to a substrate rail. The substrate rail is comprised of 10-foot sections of 3-inch angle iron which are bolted together and secured to the streambed using rebar stakes. The floating panels block fish migration and direct the fish to one of four trap boxes; these boxes can be placed in different positions as needed. There are currently three upstream trap boxes---two on one side of the river and one on the opposite bank. There is also one downstream trap box. Now that the substrate rail is in place, the weir can be installed in approximately 2 days and removed in only a few hours.

The new Elwha weir fished for 30 days in 2010 and captured a total of 492 adult salmon and trout, representing eight different species, including Chinook, pink, chum, coho, and sockeye salmon, steelhead, cutthroat trout, and bull trout. Chinook salmon were captured in the greatest number---461 individuals. Pink salmon were the next most common species captured with 12 individuals.  Although the weir was pulled prior to the peak of the coho and chum salmon runs, both species were captured. In addition, summer-run and/or early returning winter-run steelhead were captured.  The capture of pink salmon surprised us, since pinks generally return to Puget Sound rivers only during odd years (2009, 2007, etc.). They have, however, become more common during even years over the last decade.
 

The weir fishing at 2,200 cfs

The weir is planned to fish a majority of the time during the summer and early fall, when Chinook and pink salmon are migrating into the Elwha River. However, it is expected to fish only part-time during late fall through spring when storms and/or snow melt result in high water in the river. The weir fished successfully during flows of 2,200 cubic feet per second (cfs) in late summer (500 cfs is the normal low flow during summer). This was encouraging, since the weir was predicted to be able to fish up to about 2,000 cfs. 

The weir is planned to be re-installed in early 2011 to direct adult steelhead to the river margins where they will be counted using SONAR. The trap boxes will be installed in late winter or early spring to trap adult steelhead. The weir will be removed again during the spring snow melt and then reinstalled with traps as flows begin to decrease in early summer.

This project was funded in part by funds provided to the cooperating agencies as part of their annual budget.  Additional funds were obtained through the President’s stimulus program (American Recovery and Reinvestment Act). The project is currently funded through September 30, 2012.

Here are some of the fish captured by the weir:



Chinook salmon

 

Coho salmon

Chum salmon



Pink salmon



Sockeye salmon



Bull trout



Cutthroat trout

 

Steelhead