Complexities, context, and new information about the Elwha River

Recently, Hand et al. (2018) discussed the socio-ecological complexities surrounding natural resource policy, science, and management in the Columbia River Basin, using a case study of dam removal on the Elwha River in Washington State (WebFigure 1a). We feel compelled to provide additional historical context and correct some of the information provided by Hand et al. about the Elwha. The historic removals of the two Elwha River dams – a long-anticipated project that was decades in the making – have been touted by some as an environmental success story following the project's completion in 2014. As with any complex endeavor, critical analyses and lessons learned continue to emerge, and will likely benefit future projects. Dam construction along the Elwha effectively limited five Pacific salmon species, steelhead, and other migratory fish to the lower 8 km of the river, starting a steady decline of what was a highly productive salmon-producing river. In the decades following the completion of the Elwha Dam in 1913 and the Glines Canyon Dam in 1927, systematic channelization, wood removal, regulated flow/temperature fluctuations, diminished gravel recruitment, and floodplain alterations reduced the available habitat to <10% of its historical extent and led to further population declines of native salmonids and other anadromous fishes (WebFigure 1b). An important contextual element missing from their article is the massive amount of sediment released during and after dam removal (Warrick et al. 2015). Cumulatively, the dams’ two reservoirs contained 21 million cubic meters of sediment, 66% of which has since been released (Randle et al. 2015; Ritchie et al. 2018) and transported downstream to the coast (Foley et al. 2017). Because of expected high and prolonged suspended sediment concentrations during and after dam removal, a desire to re-establish functioning floodplains in the former reservoirs, and requirements to protect fishes listed under the US Endangered Species Act, a staged dam removal lasting 3 years was necessary. Preserving salmon stocks from high sediment levels (approaching 1000 times greater than background; Magirl et al. 2015), unstable bed conditions, filling of pools, and the loss of downstream floodplain channels (East et al. 2015) was accomplished through the use of an integrated program that included hatcheries, adult relocations, and natural recolonization (Figure 1), an approach that is not new to salmon reintroduction efforts (Anderson et al. 2014). A tagged adult coho salmon released into a tributary of the Elwha River in 2017 as part of a long-term program to protect fish from high suspended-sediment affected areas downstream of the dam removal project. M McHenry, Lower Elwha Klallam Tribe While not disputing the science demonstrating the potential for negative consequences of fish hatcheries, we feel that Hand et al. may have mischaracterized the role and recent history of the two Elwha hatcheries. While claiming that the use of hatcheries has created an obstacle to fish recovery, they imply that the influence of hatchery origin fish is new to the Elwha because of dam removal; this is not the case. Recent otolith marking data revealed that natural Chinook spawners were failing to replace themselves (Weinheimer et al. 2017), suggesting that the hatchery played a role in conserving native Elwha River Chinook prior to dam removal. Most Chinook and coho salmon currently recolonizing areas upstream of the former dams were born in the hatcheries. Importantly, members of the natural-origin progeny of those post-dam removal colonizers, particularly for coho, are returning to upstream areas to spawn (Liermann et al. 2017). Thus far, a positive response in terms of increased spatial distribution, fry density, and smolt production has been observed in areas that have not had anadromous fishes for decades (Liermann et al. 2017; McHenry et al. 2017). Continued monitoring and adaptive management of the Elwha River's salmon populations will be necessary to track the evolution of this response. Guidelines for such adaptive management, which recommend biologically based phases of recovery and levels of management intervention necessary to achieve restoration success, are outlined in Peters et al. (2014). The numbers of hatchery releases during and after dam removal (1.3–3.4 million per year) are lower than pre-dam removal levels (WebFigure 1c) and those prescribed during pre-dam removal planning. This contrasts with the 7 million annual releases cited by Hand et al. Additionally, other migratory species that are not and have never been in hatcheries (eg bull trout, Pacific lamprey) are also recolonizing upstream of the dams (eg Moser and Paradis 2017; Quinn et al. 2017). Lastly, a commercial and sport-fishing moratorium, in place for the past 6 years, was designed to aid in the recovery of fish populations. Hand et al.'s statement that hatchery construction or operation costs have siphoned funds away from research and monitoring budgets is inaccurate, with the Elwha being among the best-studied dam removals in the world. Funding for dam removal began in 1995 and was provided by multiple congressional appropriation bills through 2015 to cover costs associated with acquisition, dam removal, and project mitigation. Reconstruction of the tribal fish hatchery to mitigate dam removal effects to the original hatchery's water supply was provided by the American Recovery and Reinvestment Act of 2009, federal funding made available for “construction-ready” projects in response to the 2008 financial crisis. Our era's natural resource issues are inherently complex and fraught with interconnected social, legal, cultural, and ecological entanglements. For any project, a foundation built on complete information and proper context must be used within translational scientific approaches (Enquist et al. 2017) and multidisciplinary collaborations to bridge the gap between research and practice. Steeped in a complex socio-ecological history, the Elwha River restoration has seen both early successes and setbacks, with the ultimate outcomes and lessons unfolding in the decades to come. 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