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A Riverscape Perspective of Pacific Salmonids and Aquatic Habitats Prior to Large-Scale Dam Removal in the Elwha River, Washington, USA

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A Riverscape Perspective of Pacific Salmonids and Aquatic Habitats Prior to Large-Scale Dam Removal in the Elwha River, Washington, USA University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Publications, Agencies and Staff of the U.S. Department of Commerce U.S. Department of Commerce 2011 A riverscape perspective of Pacific salmonids and aquatic habitats prior to large-scale dam removal in the Elwha River, Washington, USA S. J. Brenkman National Park Service, [email protected] J. J. Duda U.S. Geological Survey C. E. Torgersen U.S. Geological Survey E. Welty University of Colorado G. R. Pess NOAA Northwest Fisheries Science Center See next page for additional authors Follow this and additional works at: https://digitalcommons.unl.edu/usdeptcommercepub Part of the Environmental Sciences Commons Brenkman, S. J.; Duda, J. J.; Torgersen, C. E.; Welty, E.; Pess, G. R.; Peters, R.; and Mchenry, M. L., "A riverscape perspective of Pacific salmonids and aquatic habitats prior ot large-scale dam removal in the Elwha River, Washington, USA" (2011). Publications, Agencies and Staff of the U.S. Department of Commerce. 243. https://digitalcommons.unl.edu/usdeptcommercepub/243 This Article is brought to you for free and open access by the U.S. Department of Commerce at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Publications, Agencies and Staff of the U.S. Department of Commerce by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. Authors S. J. Brenkman, J. J. Duda, C. E. Torgersen, E. Welty, G. R. Pess, R. Peters, and M. L. Mchenry This article is available at DigitalCommons@University of Nebraska - Lincoln: https://digitalcommons.unl.edu/ usdeptcommercepub/243 Fisheries Management and Ecology Fisheries Management and Ecology, 2011 A riverscape perspective of Pacific salmonids and aquatic habitats prior to large-scale dam removal in the Elwha River, Washington, USA S. J. BRENKMAN National Park Service, Olympic National Park, Port Angeles, WA, USA J. J. DUDA U.S. Geological Survey, Western Fisheries Research Center, Seattle, WA, USA C. E. TORGERSEN & E. WELTY1 U.S. Geological Survey, Forest and Rangeland Ecosystem Science Center, University of Washington, College of Forest Resources, Seattle, WA, USA G. R. PESS NOAA Northwest Fisheries Science Center, Seattle, WA, USA R. PETERS U.S. Fish and Wildlife Service, Lacey, WA, USA M. L. MCHENRY Lower Elwha Klallam Tribe, Port Angeles, WA, USA Abstract Dam removal has been increasingly proposed as a river restoration technique. In 2011, two large hydroelectric dams will be removed from Washington State’s Elwha River. Ten anadromous fish populations are expected to recolonise historical habitats after dam removal. A key to understanding watershed recolonisation is the collection of spatially continuous information on fish and aquatic habitats. A riverscape approach with an emphasis on biological data has rarely been applied in mid-sized, wilderness rivers, particularly in consecutive years prior to dam removal. Concurrent snorkel and habitat surveys were conducted from the headwaters to the mouth (rkm 65–0) of the Elwha River in 2007 and 2008. This riverscape approach characterised the spatial extent, assemblage structure and patterns of relative density of Pacific salmonids. The presence of dams influenced the longitudinal patterns of fish assemblages, and species richness was the highest downstream of the dams, where anadromous salmonids still have access. The percent composition of salmonids was similar in both years for rainbow trout, Oncorhynchus mykiss (Walbaum), coastal cutthroat trout, Oncorhynchus clarkii clarkii (Richard- son) (89%; 88%), Chinook salmon, Oncorhynchus tshawytscha (Walbaum) (8%; 9%), and bull trout, Salvelinus confluentus (Suckley) (3% in both years). Spatial patterns of abundance for rainbow and cutthroat trout Correspondence: Samuel Brenkman, National Park Service, Olympic National Park, 600 East Park Avenue, Port Angeles, WA 98362, USA (e-mail: [email protected]) 1Present address: Institute of Arctic and Alpine Research, University of Colorado, Campus Box 450, Boulder, CO 80309, USA. Published 2011. This article is a U.S. Government work and is in the public domain in the USA. doi: 10.1111/j.1365-2400.2011.00815.x 1 2 S. J. BRENKMAN ET AL. (r = 0.76) and bull trout (r = 0.70) were also consistent between years. Multivariate and univariate methods detected differences in habitat structure along the river profile caused by natural and anthropogenic factors. The riverscape view highlighted species-specific biological hotspots and revealed that 60–69% of federally threatened bull trout occurred near or below the dams. Spatially continuous surveys will be vital in evaluating the effec- tiveness of upcoming dam removal projects at restoring anadromous salmonids. KEYWORDS: dam removal, recolonisation, riverscape, salmonid, snorkel survey. respectively) constructed in the early 1900s on the Introduction park’s Elwha River eliminated access for anadromous The placement of hydroelectric dams on rivers causes salmonids to some 95% of the watershed. physical and biological effects that operate at multiple Prior to dam construction, there were eight species spatial scales (Rosenberg et al. 1997; Petts & Gurnell of Pacific salmonids, including a large-bodied form of 2005). Attenuated annual and seasonal discharge Chinook salmon, Oncorhynchus tshawytscha (Wal- cycles, disrupted sediment and wood transport, altered baum), with some individuals exceeding 45 kg (Wun- nutrient dynamics and increased water temperatures derlich et al. 1994; Roni & Quinn 1995). Estimates of have been widely documented in regulated rivers historical population sizes describe a river that pro- (Baxter 1977; Petts 1984; Hart et al. 2002). In the duced large numbers of salmonids relative to other Northwestern United States and elsewhere, large regional rivers (Wunderlich et al. 1994; Winter & hydroelectric projects have multiple, interacting effects Crain 2008). Pacific salmonids that inhabit the Elwha on fish populations, including the decline of anadro- River are now at critically low numbers, and anadro- mous salmonids (Raymond 1979; Kareiva et al. 2000; mous populations are limited to the lowest 7.5 river Williams et al. 2005), changed evolutionary trajecto- kilometres (rkm) below the lower dam, where there are ries of life-history strategies (Williams et al. 2005), fish no facilities providing upstream passage for anadro- migration patterns that are altered within individual mous fish. rivers (Lignon et al. 1995) and disrupted hydrological Removal of the two Elwha River dams, scheduled to connectivity (Fullerton et al. 2010). begin in 2011, will occur over a 2- to 3-year period. Dam removal has been increasingly proposed for This project – the concurrent removal of two high river restoration (Bednarek 2001; Hart et al. 2002; dams (12 km apart) in a river that drains directly into Heinz Center 2002, Stanley & Doyle 2003). Dam marine waters – will be one of the largest dam removal projects completed to date have typically removals in terms of structural height and sediment involved low-head dams with structural heights of release in North America and is the second largest <6 m (Heinz Center 2002; Doyle et al. 2005). Larger ecological restoration project in the National Park dam removal projects have occurred, or are planned, at Service (the first being Everglades restoration). locations across the western United States, including Although primarily intended to restore anadromous Matilija Dam (Ventura Basin, CA), Marmot Dam fish populations, the dam removal project is becoming (Sandy River, OR), Savage Rapids Dam (Rogue River, a living laboratory for studying the ecological effects of OR), Condit Dam (White Salmon River, WA), Klam- dam removal and river restoration and could serve as ath River Dams (OR and CA) and the Glines Canyon an important benchmark for future dam removal and Elwha Dams (Elwha River, WA). These dam projects (Duda et al. 2008). removal projects provide opportunities to examine the A key to studying watershed recolonisation by responses of fish populations, particularly Pacific Pacific salmonids after a large-scale dam removal is salmonids, to dam removal. the collection of spatially continuous baseline infor- Olympic National Park (ONP), a World Heritage mation before dam removal. In the Elwha River, Site and Biosphere Reserve located on Washington numerous baseline studies exist (see Winter & Crain State’s Olympic Peninsula, contains one of the largest 2008), and recent research has characterised charac- contiguous areas of relatively pristine habitat terised existing fish communities and predicted the (373 525 ha) throughout the range of several western responses of Pacific salmonids to dam removal (Brenk- US coastal fish species. The park contains 12 major man et al. 2008a,b; Connolly & Brenkman 2008; Burke watersheds and some 5600 km of rivers and streams. et al. 2008; Pess et al. 2008; Roni et al. 2008; Winans However, two large hydroelectric dams (Elwha Dam et al. 2008; Duda et al. in press). Although these and Glines Canyon Dam, 64 and 32 m in height, studies provide useful baseline information, most were Published 2011. This article is a U.S. Government work and is in the public domain in the USA. RIVERSCAPE PERSPECTIVE PRIOR TO DAM REMOVAL 3 conducted at the site scale, within index reaches, or on the main stem Elwha River from rkm 65 to rkm 0; (2) a section of the river downstream of the dams, and assess the patterns of species composition, relative were not spatially continuous. Because the dynamics of abundances and relative
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