Eradication of Nonnative Trout and the Response of Threatened Bull Trout at Crater Lake National Park: Extending Conservation Across Park Boundaries to a Watershed Scale David K. Hering and Mark W. Buktenica, Crater Lake National Park EXPERIENCE YOUR AMERICA
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Bull Trout (Salvelinus confluentus) USFWS photo
Bull Trout (Salvelinus confluentus) A char related to Brook Trout, Lake Trout, Dolly Varden, White-spotted Char, Arctic Char. Historic Range Historically ranged from northern California and Nevada to northern Canada; now extirpated from California One of the coldest temperature tolerances of any North American salmonid; multiple life history patterns from stream residence to anadromy. (Western Native Trout Campaign)
Bull Trout in the Upper Klamath Basin Bull trout were once widely distributed, but at least 40% of historical populations in the basin have experienced recent extirpation (Buchanan et al. 1997). Listed as Threatened under ESA in 1999 Threats and limiting factors: habitat degradation lack of connectivity nonnative trout
Introduced Brook Trout (NPS stocking records from National Archives, Seattle)
Introduced Brook Trout Bull Trout + = Brook Trout Brook Trout x Bull Trout Hybrid Pretty, but Sterile!
Sun Creek Watershed: Land Use
Sun Creek Watershed: Fish Community Bull Trout historically occupied entire stream below a headwater falls. Redband Trout may also have been present (Wallis 1948). Bull Trout distribution became severely truncated in sympatry with Brook Trout and Brown Trout. By 1989, <200 adult Bull Trout remained in Sun Creek (Dambacher et al. 1992)
Upper Sun Creek Fish Restoration: 1992-2010 (Buktenica et al. 2013, NAJFM) Objective Eradicate nonnative trout and monitor bull trout response Methods Artificial barriers installed to exclude nonnatives. Multiple years of electrofishing removal. Established refuge populations of bull trout Treated targeted reaches in 1992, 1998, 2000, 2004, and 2005 with piscicide Antimycin-A Annual snorkel survey to monitor effectiveness and bull trout recovery.
Upper Sun Creek Fish Restoration: 1992-2010 (Buktenica et al. 2013, NAJFM)
Upper Sun Creek Fish Restoration: 1992-2010 (Buktenica et al. 2013, NAJFM)
Upper Sun Creek Fish Restoration: 1992-2010 (Buktenica et al. 2013, NAJFM) Results No nonnative trout in upper watershed since 2005, no hybrids since 2010 Bull Trout abundance increased tenfold from 1980s Distribution expanded from <2 km to 11.6 km. By 2010, Bull Trout were moving downstream over exclusion barriers. 2000 1600 Bull Trout Observed by Snorkeling Estimated Bull Trout Abundance (95% C.I.) Number of Bull Trout 1200 800 400 0 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 Year
Lower Sun Creek Fish Restoration: 2010-present Restoration Opportunity 7 kilometers of suitable Bull Trout habitat downstream of NPS exclusion barriers Reach contained high densities of Brook Trout and Brown Trout and was a sink for Bull Trout that move downstream. Objective Partner with state agencies to eradicate nonnative trout and extend Bull Trout distribution downstream of National Park Methods Installed new exclusion barriers in 2010. Characterize pre-treatment community and salvage Bull Trout by electrofishing Two successive treatments with Antimycin-A, 2012 and 2013 Post-treatment electrofishing to evaluate effectiveness
Lower Sun Creek Fish Restoration: 2010-present
Lower Sun Creek Fish Restoration: 2010-present
Lower Sun Creek Fish Restoration: 2010-present
Lower Sun Creek Fish Restoration: 2010-present Results: Nonnative Removal 2012 chemical treatment removed estimated 7300 Brook Trout and 220 Brown Trout 2013 treatment removed at least 4 remaining Brook Trout Salvaged 96 Bull Trout over two years, but recovered 68 Bull Trout mortalities Post-treatment electrofishing in 2014 detected only Bull Trout Treatment 1 Treatment 2 2008 (Pre-Treatment) 2012 (Pre-Treatment) 2013 (Post Treat 1) 2014 (Post Treat 2) n = 1852 n = 3389 n = 138 n = 60 Brook Trout Brown Trout Bull Trout Brook Trout Brown Trout Bull Trout Brook Trout Brown Trout Bull Trout
Lower Sun Creek Fish Restoration: 2010-present Results: Bull Trout Response One year post-treatment, estimated 188 Bull Trout (95% CI 60-313) colonized the treated reach. Bull Trout densities were highest upstream near source population. Bull Trout are now distributed throughout treatment area and occupy 85% of the Sun Creek watershed. 25 Bull Bull Trout per per 100m 100m 20 15 10 5 NPS Exclusion Barrier 2014 Bull Trout ODF Exclusion Barriers 0 14 15 16 17 18 19 20 21 22 Distance Kilometers from from Headwaters (km) upstream downstream
Restoring Landscape Connectivity
Restoring Landscape Connectivity
Partnerships
Conclusions A long-term, phased approach has restored native fish to 85% of Sun Creek watershed. Post-treatment monitoring and adaptive management were required to successfully eradicate nonnative fish. Bull trout have responded rapidly to recent nonnative removal. Population recovery seems to be accelerating. By partnering with other agencies and landowners, a restoration program that started in Crater Lake National Park is having farther-reaching effects outside the protected area. The Sun Creek project exemplifies how NPS can take a regional leadership role to support native species conservation. Contact: david_hering@nps.gov