The Complex Case of Colorado s Cutthroat Trout in Rocky Mountain National Park George Wright Society March 31, 2015 Greenback Cutthroat Trout??? (FWS)
Key Points There has been a substantial shift in understanding of cutthroat lineages and distribution in Rocky Mountain National Park (ROMO). Stocking occurred earlier and was more widespread than previously recognized. Cutthroat groups (lineages or subspecies) are more genetically and morphologically diverse than previously recognized. This understanding has changed the direction and strategies of the Greenback Recovery Team and other stakeholders in Colorado.
Historic Conditions Presumed Historic Fish Distribution in ROMO: Streams/Rivers in low elevation meadows Lakes below major waterfalls and cascades Based on known fish barriers and the written record. From: Kennedy, C.M. 2013. Rocky Mountain National Park fisheries and aquatic management 2013.
Settlement and Fish Stocking Stocking began in the late 1800s Stocking was done to: Replenish depleted waters Add fish to barren waters 1800s through 1968: Most lakes in ROMO >1 acre were stocked Most fish stocked were nonnative NPS photo
Metcalf et al. 2012. Historical stocking data and 19 th century DNA reveal human-induced changes to native diversity and distribution of cutthroat trout. Molecular Ecology 21:5194-5207. Rocky Mountain National Park Traditional Geographic Model FWS photo Colorado River Cutthroat Trout FWS photo Greenback Cutthroat Trout Rio Grande Cutthroat Trout
Traditional Geographic Model Traditional Model Separation based on geography and meristics. Genetics studies before ~2000 could not tell the cutthroat subspecies in ROMO apart. Recovery goals were nearly met. Recovery team was taking the final steps prior to de-listing recommendation. Emerging Scientific Information Nuclear DNA (microsatellites) appeared able to separate ROMO cutthroats. The genetic picture across the range was a mix of the two subspecies.
Metcalf et al. 2007 Blue = Colo. River cutthroat trout Green = Greenback cutthroat trout Study findings included: >50% of greenback populations studied were genetically Colorado River cutthroat. The Colorado River cutthroat east of the divide were likely stocked. No explanation for the greenback population west of the divide. Hunter s Creek was significant to the greenback broodstock program and was genetically Colorado River.
Lesson Learned #1 Manage Your Message Study: Biologists trying to save endangered trout used wrong fish Efforts To Save Greenback Cutthroat Trout Snagged: Wrong Fish Restocked For Decades
Rogers 2012 Colorado Parks and Wildlife AFLP study Sampled 254 cutthroat populations west of the divide (presumably Colorado River cutthroat). 54 assigned with greenback. More greenback populations west of the divide than east.
Lesson Learned #2 ID key issues and work to resolve them Use what you know: Stocking was influencing the distribution and we needed to remove its influence. Stocking records were incomplete. Early pre-stocking museum samples were available. So what? if it walks like a duck To find out what you need: Compile all the stocking records available. Research newspapers and other historic documents. Develop a genetic study to use museum samples to identify the historic distribution. Develop a meristic study to see if cutthroat can be separated by physical characteristics.
Metcalf et al. 2012 museum study Study methods: Ancient DNA Samples from the pre-stocking era (1857-1889) Samples from 7 basins in CO and NM Compared museum and contemporary populations Exhaustive search for stocking data
Metcalf et al. 2012 museum study Geographic Model vs. Genetic Model Study findings: Six divergent lineages in CO; two believed to be extinct The South Platte native cutthroat (greenback) exists in only one stream
Metcalf et al. 2012 museum study Native cutthroat Colorado Sources 1899-1909: Grand Mesa Lakes, Gunnison, CO 29 million fish stocked Stocked in lakes and streams in all major drainages in CO 1903 began; 1914 1925: (Trappers Lake): 26 million fish stocked Stocked in all major drainages in CO
Bestgen et al. 2012 meristic study
Bestgen et al. 2012 meristic study
Bestgen et al. 2012 meristic study Colorado River native to Yampa, Green, lower Colorado Green lineage - native to upper Colorado, Gunnison, Dolores Bear Creek South Platte native Rio Grande cutthroat
Lesson Learned #3: Once uncertainty is resolved, re-engage and move forward FWS Leadership Group MOU FS, FWS, BLM, NPS, Colorado Parks and Wildlife Recovery Team Terms and Conditions Broodstock Management Recovery Outline Advocate to expand Bear Creek (the true greenback) Front Range Cutthroat Trout Collaborative Group ID opportunities for on-the-ground recovery
Discussion and Questions?