Rio Grande cutthroat trout (RGCT; Oncorhynchus clarkii virginalis); Westslope cutthroat trout (WCT; Oncorhynchus clarkii lewisi)
Carter G. Kruse
Range-wide declines primarily due to competition and introgression with introduced salmonids, but also from habitat degradation and exploitation. RGCT were historically found in about 10,700 km of habitat in the upper Rio Grande basin of Colorado and New Mexico, however the distribution of genetically pure populations of this subspecies has been reduced by 92%. WCT were historically the most widespread cutthroat subspecies – occupying an estimated 90,800 km of streams and rivers throughout the Columbia and Missouri basins headwaters of Montana, Wyoming and Idaho – but the range of genetically pure populations has been reduced by 76%. On the east side of the Continental Divide range reduction has been even more dramatic, exceeding 95%.
RGCT were listed as a federal candidate species under the Endangered Species Act (ESA) in 2008 and are currently undergoing another status review for listing determination. The subspecies is considered a Species of Greatest Conservation Concern/Need by the New Mexico Department of Game and Fish and Colorado Parks and Wildlife. WCT are not listed under ESA, but are considered a Species of Greatest Conservation Need by Montana Fish Wildlife and Parks and Idaho Department of Fish and Game. Both subspecies are considered Sensitive by the US Forest Service.
Project Goals & Objectives
Range-wide conservation agreements among management agencies and non-governmental organizations are in place to guide conservation and restoration activities for WCT and RGCT across jurisdictional boundaries. Objectives outlined in these documents include: securing and monitoring known cutthroat trout populations; seeking opportunities to restore or found new populations, especially over large areas and including private lands; identifying or locating any additional wild populations; coordinating conservation activities among resource agencies and non-governmental organizations; and providing public outreach and technical assistance. These range-wide objectives for cutthroat trout conservation are consistent with the mission of Turner Enterprises and fit within the land management framework on the ranches. Most importantly, the Turner family has been supportive of cutthroat restoration, embracing the risks inherent with large-scale native trout restoration. The Turner Biodiversity Divisions have developed a Cutthroat Trout Initiative with a goal of catalyzing cutthroat restoration or conservation activities on 400 km of stream. This is by far the most comprehensive and ambitious private effort on behalf of native cutthroat trout. Efforts to restore or conserve cutthroat trout are in planning or underway in eight streams on four ranches; not all may ultimately be implemented or successful but they provide the framework to reach our goal. These projects all have similar objectives, with an overall intent of improving the range-wide status of RGCT and WCT and preventing listing under ESA:
1. Selection of re-introduction sites encompassing a large geographic area with high quality and diverse habitats to support a robust cutthroat trout population with diverse life-history strategies able to resist threats such as climate change, catastrophic events, and invasive species.
2. Elimination of non-native competitors in the re-introduction site (watershed or portion thereof) through physical and/or chemical renovation, and prevent their recolonization.
3. Establishment of a self-sustaining population of cutthroat trout large enough to withstand environmental and demographic stochasticity and likely to persist over the long-term (> 100 years) with little or no human intervention.
4. Establishment of a monitoring strategy, including relevant research partnerships, that evaluates key project aspects and allows adaptive management of all strategies and methods as the project unfolds, and to improve and guide future efforts.
The cutthroat trout is native to the Rocky Mountain and coastal areas of the western United States (US) and is classified into as many as 14 subspecies. The seven major (based on distribution) inland subspecies of cutthroat trout historically occupied most accessible cold water environments from Canada to southern New Mexico. However, all subspecies have incurred significant range reductions primarily due to competition and introgression with introduced salmonids, but also from habitat degradation and exploitation. Lahontan (O. c. henshawi) and greenback (O. c. stomias) cutthroat trout are listed as threatened under the US Endangered Species Act (ESA) and the other inland subspecies have either been petitioned for listing under the ESA or are considered species of concern by state and federal agencies. Recovery and conservation efforts are underway for all major subspecies, with many notable successes; however such efforts are hindered by ongoing non-native invasions, limited opportunities for large-scale projects, social resistance, changing habitat conditions (e.g., climate change), and past, widespread introductions of cutthroat trout subspecies outside their native ranges.
The Turner organization and ranches are ideally situated to play an important role in cutthroat trout conservation. The Flying D, Snowcrest, Vermejo Park, and Ladder ranches all contain large, connected sections of high quality cold water stream habitat within the historic range of WCT and RGCT. In conjunction with neighboring public lands these ranches encompass entire stream headwaters, an important consideration when prioritizing and securing restoration sites. Although small restoration projects (e.g., <15 km of stream) are important to preserve presence and genetic variability on the landscape, cutthroat conservation projects most likely to succeed over the long-term are those that encompass large areas allowing expression of multiple life histories and connecting multiple, local sub-populations – inferring a better chance of withstanding localized extinctions and changing habitat conditions. Through the RGCT and WCT Range-Wide Conservation Working Groups, Turner Biodiversity has partnered with public agencies and other private organizations to implement two of the largest cutthroat trout restoration projects ever undertaken in the United States.
The Costilla Creek Native RGCT Project on Vermejo Park ranch in New Mexico and Colorado is the most ambitious watershed renovation project ever initiated on behalf of any cutthroat trout, encompassing approximately 175 km of stream habitat (50% on Vermejo Park Ranch) and 18 lakes. Initial project planning in 1998 included only 25 km of stream and four lakes; but with successful application of piscicides in 2002 and population recovery by 2004, the project area was expanded in 2007 to its current size. An expanded project, with a larger area and more diverse habitat, improves the likelihood that restored RGCT in Costilla Creek will persist long term. The project is complicated due to its unprecedented size, regulatory requirements, need for at least seven man-made, temporary fish movement barriers to facilitate treatment in “phases”, a 15,700 AF reservoir, and social pressures. To date over 100 km of stream have been chemically renovated, with 48 km of the approximately 85 km of suitable stream habitat on Vermejo Park Ranch completed. If this project is fully implemented as scheduled by 2020 it will represent a 20% increase in the amount of stream genetically pure RGCT currently occupy within their historical range. This project would not have been initiated without Turner support and is the flagship restoration effort on behalf of RGCT for the NM Department of Game and Fish. Planning and implementation of the Costilla Project is largely responsible for the development of consistent NM state guidelines regarding the use of piscicides, and for re-development of the Department’s native cutthroat trout hatchery broodstock; both important steps for range-wide restoration and conservation of the species.
The Cherry Creek Native WCT Project on the Flying D Ranch in Montana encompasses approximately 100 km of stream habitat and 3 hectares of lake habitat suitable for cutthroat trout, and is the largest piscicide renovation project ever completed for the purpose of cutthroat trout conservation. The project began with establishment of a collaborative working group, feasibility analyses, and environmental planning in 1997. Opposition to the use of piscicides and nonnative fish removal, through a series of legal and administrative challenges, delayed initial piscicide application until 2003. Piscicide applications were completed in 2010. In 2006, WCT introductions began via remote stream-side egg incubators and were completed by stocking young of year fish in 2012. Approximately 37,000 eyed eggs and 8,500 young of year fish from multiple wild populations and a hatchery conservation broodstock were introduced to the project area. WCT are now found throughout the project area and successful reproduction is occurring – two important benchmarks of success. The Cherry Creek project is a significant conservation achievement for WCT on the east side of the continental divide. This project increases the stream km occupied by WCT in the Madison River basin from 7 km to over 100 km or from 0.3% of historical occupancy to almost 5%. Perhaps more importantly the success of the Cherry Creek project, and lessons learned from, has catalyzed several other cutthroat trout re-introduction projects in southwestern MT. The scope of this project has allowed innovative research on relative survival, growth and dispersal of cutthroat trout source stocks; the impacts of piscicides on non-target organisms; movement and colonization of fish in renovated habitats; and the genetic fitness of multiple source stocks. To date, five graduate students have used different aspects of the project to receive doctoral and master’s degrees. This research and resulting publications in peer reviewed scientific journals will be invaluable to guide and improve future aquatic conservation efforts. Turner Biodiversity Divisions have assisted MT FWP and USFWS with the development of a Candidate Conservation Agreement with Assurances (CCAA) for westslope cutthroat trout in MT, and Cherry Creek was one of the first conservation areas to be included under the CCAA.