BLM Colorado

BLM Colorado

Tuesday, October 18, 2016

Re-Introduction of Greenback Cutthroat Trout to Herman Gulch, Colorado


Re-Introduction of Greenback Cutthroat Trout to Herman Gulch, Colorado
Our understanding and knowledge of the distribution and status of cutthroat trout in Colorado has changed dramatically in the past decade.   Historically, greenback cutthroat trout (Oncorhynchus clarkii stomias) were thought to occupy the South Platte and Arkansas River basins in eastern Colorado.  
Colorado River cutthroat trout (Oncorhynchus clarkii pleuriticus) were believed to occupy high elevation streams and lakes in western Colorado -- with the Continental Divide serving as a geographic barrier separating the two subspecies.  A third subspecies, the Rio Grande cutthroat trout (Oncorhynchus clarkii virginalis), was found exclusively in the Rio Grande River basin.
Pure GBCT from Bear Creek in Colorado
Concerted research efforts starting in 2003 have since further clarified the native distribution of these fish culminating in 2012 with a study that combined an extensive search of remaining stocking histories combined with molecular analysis of museum specimens collected up to 150 years ago and extant populations (Metcalf et al. 2012).
This research concluded that greenback cutthroat trout (GBCT) were native only to the South Platte River basin, and surprisingly, that only a single population remained.  This population in Bear Creek near Colorado Springs appears to have been founded from stock collected in the South Platte River basin in the late 1800’s.  These fish have survived as an isolated self-sustaining pure population of GBCT above a natural waterfall in just four miles of habitat for over 130 years. 
Based on Metcalf’s (2012) findings, and a more recent study that demonstrated Bear Creek fish are visually distinct from other cutthroat trout (Bestgen et al. 2013), current GBCT recovery efforts are now focused on replicating the Bear Creek GBCT in hatcheries and re-establishing populations within their native South Platte River basin. 

Volunteers gather at the Herman Gulch Trailhead to collect GBCT for the hike to stocking locations

Matt Fairchild (USFS) allows fish to acclimate to the water temperature in Herman Gulch prior to their release

Jay Thompson (BLM) prepares to release the fingerling GBCT into their new home in Herman Gulch

Mary Kay Watry (NPS) celebrates her arrival at stocking point #12 approximately 5 miles from the trailhead

Herman Gulch is a small headwater stream in the South Platte River basin and originates high on the east side of the Continental Divide near Interstate 70 in Colorado.  Following a salvage effort to relocate the existing mixed lineage cutthroat trout and subsequent reclamation of Herman Gulch, a group of hardy individuals gathered on September 13 to carry pure greenback cutthroat fingerlings in backpacks to the upper reaches of Herman Gulch.  These fingerlings were offspring from Bear Creek (the only remaining pure population of GBCT) and were delivered to the trailhead from the Colorado Parks and Wildlife (CPW) hatchery in Salida, Colorado. 
At the trailhead, the fish were placed in sealed and aerated plastic bags inside insulated pouches for the journey to their new home.  Biologists and volunteers from CPW, Trout Unlimited, BLM, NPS, and the USFS were assigned to hike the fish to one of sixteen pre-determined stocking sites ranging from one to six miles up the trail. 

All of the “fish haulers” quickly realized three things:  the air is thin above 10,000 feet; the Herman Gulch trail is steep; and water is really heavy!  Undaunted, the fish were successfully delivered to all 16 sites and released into their new home.  Follow up surveys indicate good initial survival and surveys next spring will determine overwinter survival.  Depending on survival, another round of stocking may be scheduled after next spring’s runoff. 

Stocking team members from FWS, USFS, CPW, and BLM at the stocking site just below the Continental Divide