North Platte Wild Trout

The upper North Platte River flows from its headwaters in northern Colorado through Northgate Canyon and onto the broad Saratoga Valley in Wyoming. The wild trout fishery along the mainstem North Platte south of Interstate 80 is widely regarded as one of the West’s finest. In Colorado and Wyoming, the North Platte has 130 continuous miles of “Blue” (Ribbon) (WY) or “Gold Medal” (CO) waters. Major tributaries include the Encampment River, Douglas Creek, Big Creek, Illinois River, Michigan River, and Canadian River. Within the mosaic of private and public ownership, the U.S.D.A. Forest Service manages much of the forested headwater tributaries and the Bureau of Land Management manages the lower elevation shrublands. Other public land holders include Wyoming and Colorado state lands and the Arapaho National Wildlife Refuge. Private lands are spread across the basin and mostly include hay fields, pastures, range lands, and low-density urban development.

Trout are not native to the North Platte River but brook trout and rainbow trout were first stocked in the 1880s. Today, brown trout and several subspecies of cutthroat trout (Yellowstone, Colorado River, and Snake River finespotted) can be caught in the basin. The Wyoming Game and Fish Department began managing the North Platte as a wild trout fishery in the early 1980s, but the Colorado Division of Wildlife still stocks rainbow trout in portions of the mainstem.

There are several threats to the valuable North Platte trout fishery. The productivity of the system depends on the ability of mainstem fish to access spawning habitat in tributary streams. Increased development of surface and groundwater for agriculture and residential uses may decrease stream connectivity. Continued oil and gas exploration in North Park and development of oil, wind, coal, and uranium near I-80 threaten the future security of the fishery as water quality is degraded by water withdrawals, pollutants, and road building. Furthermore, energy development in North Park could degrade water quality in the Platte River Wilderness, just downstream. An additional threat comes from changing land use patterns in the basin with the influx of permanent and temporary workers for the energy boom and continued second home development. A more acute threat is the ongoing mountain pine beetle outbreak that is causing extensive mortality of lodgepole pine, Engelmann spruce, and subalpine fir throughout the Colorado and Wyoming Rockies. This outbreak appears linked to prolonged drought caused by a changing climate and both past and present management decisions related to timber harvest. Large, homogenous stands of beetle-killed trees increase wildfire risk. Beyond fire risks, the outbreak may also alter hydrology, decrease stream shading, influence large wood inputs, and increase salvage logging activity – all of which can adversely impact wild trout habitat.

North Platte Analysis Area

Our CSI for wild trout focuses on riverine trout populations and perennial streams in the North Platte Basin. This subbasin-scale CSI incorporates information not considered in the typical CSI, including:

• Trans-basin water diversions, reflected in the water quantity indicator at the subbasin scale;
• Conservation easements from the Wyoming Game and Fish Department, Wyoming Stock Grower’s Agricultural Land Trust, The Nature Conservancy, the Colorado Cattlemen’s Agricultural Land Trust, and the Legacy Land Trust, reflected in the land conversion indicator;
• Mountain pine beetle outbreak areas, included as a new Future Security indicator

Fish data were provided by Wyoming Game and Fish Department and Colorado Division of Wildlife. Because of the limited spatial extent of trout data for Colorado, population integrity findings in Colorado are based primarily on expert opinion. Potential fish migration barrier and general habitat information was provided by Jeff Streeter and the U.S.D.A. Forest Service Medicine Bow National Forest. We are grateful for their contributions to our understanding of wild trout in the North Platte River Basin. A complete list of data sources is provided separately.

Key CSI Findings

• Wild trout population integrity is high throughout the basin except in the tributaries in the northern portion (Sage Creek and downstream)
• Whirling disease has been prevalent in southeastern Wyoming since 1988 but has yet to affect the North Platte trout fishery
• Nearly 2,000 trout per mile have been recorded in the North Platte River, with the entire mainstem from Colorado to Saratoga, Wyoming, having Blue Ribbon or Gold Medal designation
• Although trout densities are high in the mainstem, there appears to be limited reproduction downstream of Sage Creek, Wyoming
• Wyoming Game and Fish Department manages the North Platte as a wild fishery, but Colorado Division of Wildlife stocks diploid rainbow trout near Delaney Buttes
• The lowest habitat integrity scores reflect decreased habitat connectivity and flow alteration associated with dams, diversions, and irrigation
• The lowest water quality scores reflect oil and gas development, high road densities, and extensive agricultural land use.
• Two streams are 303(d) listed: Sage Creek because of habitat degradation and Hot Slough Creek because of residual chlorine, ammonia, and fecal coliform from Saratoga’s waste water treatment plant.
• Resource extraction related to oil and gas, wind, coal, and uranium reserves constitutes the primary threat to future security of wild trout in most subwatersheds.
• Under a climate change scenario, the North Platte Basin is at low risk to flooding associated with rain-on-snow events but is at moderate risk to altered fire regimes and increasing stream temperatures and high risk to drought
• Dead and dying trees from the mountain pine beetle outbreak are the primary land cover in 10% of subwatersheds in the North Platte Basin, a major source of uncertainty affecting future security

Population integrity of wild trout is high throughout the North Platte River Basin except for tributary watersheds between Sage Creek and Seminoe Reservoir that lack suitable trout habitat. Trout densities in the North Platte River mainstem and lower Encampment River have been reported to be nearly 2,000 per mile. For this reason, the mainstem North Platte upstream from Sage Creek near Saratoga, Wyoming, through the Routt National Forest in Colorado has been designated as a “Blue” (Ribbon) or “Gold Medal” stream by Wyoming Game and Fish Department and Colorado Division of Wildlife, respectively. The ratio of fish from 1 to 6 inches to fish larger than 6 inches suggests that the lower mainstem below Saratoga, Wyoming, may have limited natural reproduction. Whirling disease was first documented in southeastern Wyoming in 1988, and the disease has been found in fish in the North Platte River and several tributaries; however, the disease has yet to have population-level effects in the basin. Although the Wyoming Game and Fish Department manages the North Platte as a wild fishery, the Colorado Division of Wildlife stocks diploid rainbow trout near Delaney Buttes.

Habitat Integrity in the North Platte Basin ranges from degraded to pristine. Forested, headwater subwatersheds generally have high habitat integrity, while developed subwatersheds near Walden, Colorado, and along the North Platte mainstem near Saratoga, Wyoming, have low habitat integrity. Most watersheds score low for land stewardship with the exception of protected wilderness areas in the Medicine Bow and Routt National Forests in higher elevation watersheds, reflecting the lack of formal habitat protection in the basin. Watershed connectivity is generally high, but it is lowest in developed subwatersheds where water is diverted for agricultural and municipal use. Connectivity is also reduced by additional dams and diversions in headwater streams to store and move water. Flow regimes are altered by trans-basin water projects for the City of Cheyenne in Douglas Creek and Hog Park Creek. Extensive canal networks in flat, developed subwatersheds alter water quantity.

High road densities and agricultural lands contribute to lower watershed conditions scores around Saratoga and Encampment, Wyoming. Overall water quality is high, except in energy development areas along the I-80 corridor and in North Park, and along 303(d)-identified degraded stream reaches along Sage Creek and in Saratoga. The CSI lacks a specific indicator for addressing some fine-scale stressors to the North Platte Basin, for example, cattle grazing. As a result, some habitat integrity scores may not reflect local instream habitat conditions.

Most subwatersheds have moderate scores for Future Security. Land conversion risk is moderate across the basin because undeveloped lands exist close to roads and existing urban areas. These remaining areas could experience intense development pressure from the influx of energy industry workers and continued second home development. A small portion of private lands is encumbered by conservation easements. Mining claims and energy development areas (including oil, gas and wind leases and coal and uranium reserves) are spread across the entire basin, from ridgetops to valley bottoms; most North Platte subwatersheds had low future security because of potential resource extraction. Six sites have been identified in the North Platte for future dam development. These areas, along the Michigan River in Colorado, along the mainstem North Platte in Wyoming, and on Jack Creek west of Saratoga, may become more attractive depending on climate change scenarios and future impacts to water availability, especially for existing water uses.

Forested subwatersheds scored low for future security due to the mountain pine beetle outbreak. Dead and dying lodgepole pine, Engelmann spruce, and subalpine fir are prevalent across the basin; up to 72% of the land cover in forested subwatersheds consists of dead trees. If a fire start occurs during hot summer conditions, it could quickly spread into a large, high-intensity wildfire. Such fires typically cause higher erosion rates as soils are exposed, which may lead to higher stream sedimentation rates at least during the immediate period following the fire. High intensity wildfire in the basin may be unavoidable given the large extent of dead and dying trees. Roads located along riparian areas as well as culverts (stream/road crossings) within the zone of mountain pine beetle outbreak may exacerbate stream hazards when high intensity wildfires occur. Immediate action may be needed to identify and fix stream crossings and culverts that would have a high probability of failure during debris and sediment flows following a wildfire.

Considering a 3°C increase due to climate change, the North Platte subbasin is not at risk to increased winter flooding because of more rain-on-snow events. However, warmer spring temperatures in mid-elevation watersheds are predicted to reduce moisture and alter fire regimes, and wild trout are at moderate risk to increased instream summer water temperatures. Drought severity models identify the lower elevation subwatersheds in the basin as at high risk to lower stream flows through water-loss associated with higher temperatures.

The CSI suggests that restoration efforts are especially appropriate on the lower Encampment because of the high habitat integrity and future security of the headwaters. Reconnecting the Encampment River to the mainstem North Platte will allow fluvial fish to reach important spawning reaches and increase natural reproduction. Because of its high habitat integrity and future security, Douglas Creek appears to be a good place to focus protection efforts.

Trout Unlimited strongly supports current efforts by Wyoming Game and Fish Department and Colorado Division of Wildlife to manage the North Platte River and its tributaries primarily as a wild trout fishery. The CSI analyses emphasize the importance of maintaining large interconnected habitats; such priorities will increase the resistance of existing populations to both natural and anthropogenic disturbances. Ongoing habitat restoration on impaired reaches will also improve trout habitat. Protection efforts should be targeted at areas prone to energy and ex-urban development, especially when they occur near habitats important to wild trout populations. Strategic conservation actions will keep the North Platte wild trout fishery one of the best in the West.

Prepared by Kurt Fesenmyer and Dan Dauwalter, TU, 2/3/2009

Table 1. CSI scoring result summary for North Platte Wild Trout

Conservation Strategies Map