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Catch-per-unit-effort of young-of-the-year Colorado pikeminnow seined from Colorado River backwaters, 1986–2010 (data from Breen et al. 2011), and the later strength of the corresponding year class at age-5 (see Table 8). S = strong; M = moderate; and W = weak at age 5. Strength at age-5 cannot yet be assessed for year classes of 2006–2010.
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Mark-recapture studies from 1991 through 2010 were used to assess population trends of Colorado pikeminnow Ptychocheilus lucius in the upper Colorado River. Four multi-year data collection efforts were made: 1991–1994, 1998–2000, 2003–2005, and 2008–2010. Primary objectives included capturing and marking Colorado pikeminnow > 250 mm in total length...
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... -There is extensive detailing of which Covered Actions are discretionary and which non-discretionary and how to deal with the legal uncertainties regarding these, as well as quantification of the effects of covered actions with considerable reliance on judicial mediation pathways in cases of conflicting priorities(LCR-MSCP 2005). Learning 3 -The program has conducted 5-yearly Species Status Assessments to monitor endangered fish populations and has recommended two species for delisting based on these(Elverud et al. 2020). Cooperative agreements for extension of program and funding have been implemented in 2001 and 2009 and will be renewed again in 2023.3 -Adaptive management occurs at project and program levels with review of reports and monitoring results at project level and adjustments to Habitat Conservation Plans (HCPs) requiring adjustments to funding levels, revisions to HCP conservation measures and adoption of alternative conservations measures (LCR-MSCP 2020). ...
With a particular emphasis on the Upper Colorado River Endangered Fish Recovery Program (UCR-EFRP) and Lower Colorado River Multi-Species Conservation Program (LCR-MSCP), we analyze, for each program, four system properties that contribute to resilience: system architecture, which includes (1) connectivity and distribution and (2) assemblage of system elements; and system dynamics, which includes (3) social and natural capital flows and (4) system renewal and continuation. Each of these system properties is analyzed based on specific social and corresponding biophysical indicators. The system properties were ranked on a carefully constructed scale based on gradations of each system property (derived from the literature) on both social and biophysical indicator standing. Our results indicate that the UCR-EFRP has relatively better social architecture and dynamics with relatively less impact on the ecological architecture and dynamics compared to the LCR-MSCP, though this result may be a function of the greater amount of infrastructural constriction and path dependence in the lower basin compared to the upper basin. We conclude by suggesting that a transformative pathway forward needs greater adaptability and flexibility incorporated into the social architecture and dynamics to move toward better ecological health of the river.
... As a result of differences in habitat and fish communities, the upper Colorado River Basin is considered the last stronghold for several large river fishes native to the Colorado River Basin. For example, wild populations of Colorado pikeminnow persist in the Green River and Colorado River Basins and some larger tributaries, including the Yampa River (Bestgen et al. 2007a(Bestgen et al. , 2010aOsmundson and White 2014;Bestgen et al. 2018). Colorado pikeminnow is also found in the San Juan River, but population augmentation by stocking hatchery-reared individuals is necessary to maintain the species (Platania et al. 1991;Franssen and Durst 2014). ...
... While the three rivers in the upper Colorado River Basin, the San Juan, Colorado, and Green Rivers, differ in physical attributes and extent of human modification, each supports two or more endangered fishes as well as bluehead and flannelmouth sucker, roundtail chub, and speckled dace. The Green River, which receives flow from the Yampa River, White River, and smaller tributaries (Figure 1-1) supports the largest populations of endangered as well as nonlisted native fishes (Tyus 1987;Platania et al. 1991;Bestgen 1990;Tyus 1990;Bezzerides and Bestgen 2002;Bestgen et al. 2007aBestgen et al. , 2008Bestgen et al. , 2010aZelasko et al. 2010;Osmundson and White 2014). This is a function of both larger overall habitat size and greater population densities. ...
... For example, about 900 RK (559 RM) of mainstem and tributary habitat in the Green River Basin is occupied by Colorado pikeminnow. In contrast, Colorado pikeminnow occupy about 322 RK (200 RM) in the mainstem Colorado River (Osmundson and Burnham 1998;Osmundson et al. 1997Osmundson and White 2014) and about 282 RK (175 RM) in the San Juan River (Platania et al. 1991;Holden 1999;Franssen et al. 2014). ...
The Green River and its tributaries in Utah and Colorado support populations of four
endangered fishes: humpback chub (Gila cypha), bonytail (Gila elegans), Colorado pikeminnow (Ptychocheilus lucius), and razorback sucker (Xyrauchen texanus). The Green River system is considered vital to the recovery of these federally protected species. In recognition of its importance, the U.S. Fish and Wildlife Service designated portions of the system as critical habitat under provisions of the Endangered Species Act, as amended, including the Green River downstream of the Yampa River confluence and portions of the Yampa, White, and Duchesne Rivers.
Operation of Flaming Gorge Dam, which is located on the upper mainstem Green River
in northeastern Utah, upstream of the unregulated Yampa River, influences downstream flows and temperatures, sediment transport and channel morphology, and the ecology of riverine species, including native fishes. Other human-caused perturbations to the Green River system include the introduction and proliferation of invasive nonnative fishes, water depletions, construction of levees, establishment and encroachment of nonnative vegetation, and contamination of surface water and groundwater.
To mitigate some of the adverse effects of Flaming Gorge Dam operations on endangered
fishes, a number of modifications to operations have been implemented since the dam was completed in 1962. In 1978, a selective withdrawal system (SWS) was installed to allow the withdrawal of water from different depths in Flaming Gorge Reservoir to control the temperature of releases, especially the release of warmer water. The 1992 Biological Opinion on operation of Flaming Gorge Dam recommended changes in seasonal releases from the dam and the initiation of a cooperative research program to study the effects of dam operations. Information gathered under this research program served as the basis for a set of flow and temperature recommendations published in 2000 by a multiagency team (Muth et al. 2000).
Since the Muth et al. recommendations and the subsequent Green River Study Plan were
published and implemented, a number of changes in the Green River system and the upper Colorado River Basin have occurred that could affect the appropriateness of those
recommendations. These include changes in the distribution and abundance of endangered and nonnative fishes, changes in dam operations to meet the needs of endangered fish based on new information, an extended period of drought, and changes in the condition of in-channel and off channel habitats. In addition, several syntheses of available information have been produced that shed light on the effects of the recommendations on endangered fishes in the system and point to the need for changes in the flow recommendations.
In this report, we evaluate this new information and results from studies conducted under
the Green River Study Plan and others to reassess the appropriateness of the Muth et al.
recommendations and evaluate the need for revision. Specifically, we evaluate operational, biological, and physical information collected from 2006 through 2016, and present a revised set of flow and temperature recommendations based on what has been learned since their initial implementation. As in Muth et al. (2000), our goal is to recommend, based on the most recent information available, annual and seasonal patterns of flow and temperature that will enhance populations of the endangered fishes in the Green River downstream of Flaming Gorge Dam. To achieve this goal, we identified seven objectives on the basis of species needs. With the exception of an additional objective, which focuses on control of nonnative fish populations, the goal and objectives are the same as those presented in Muth et al. (2000).
... It is important to note that this study encompasses the entire native range of this species. These results combined with the continuing recent declines in Colorado Pikeminnow abundances [54][55][56], suggests that further understand of the current THg concentrations and their spatial patterns may prove useful in identifying additional drivers of declining temporal patterns in Colorado Pikeminnow abundance. Collectively, these findings support the idea that THg and Se are stressors that may be limiting the recovery of native fishes in the UCRB along with nonnative species, flow alteration, and habitat fragmentation [10,16,57]. ...
Mercury (Hg) and selenium (Se) are contaminants of concern for fish in the Upper Colorado River Basin (UCRB). We explored Hg and Se in fish tissues (2,324 individuals) collected over 50 years (1962-2011) from the UCRB. Samples include native and non-native fish collected from lotic waterbodies spanning 7 major tributaries to the Colorado River. There was little variation of total mercury (THg) in fish assemblages basin-wide and only 13% (272/ 1959) of individual fish samples exceeded the fish health benchmark (0.27 μg THg/g ww). Most THg exceedances were observed in the White-Yampa tributary whereas the San Juan had the lowest mean THg concentration. Risks associated with THg are species specific with exceedances dominated by Colorado Pikeminnow (mean = 0.38 and standard error ± 0.08 μg THg/g ww) and Roundtail Chub (0.24 ± 0.06 μg THg/g ww). For Se, 48% (827/1720) of all individuals exceeded the fish health benchmark (5.1 μg Se/g dw). The Gunnison river had the most individual exceedances of the Se benchmark (74%) whereas the Dirty Devil had the fewest. We identified that species of management concern accumulate THg and Se to levels above risk thresholds and that fishes of the White-Yampa (THg) and Gunnison (Se) rivers are at the greatest risk in the UCRB.
... Instead, all encounters with each Northern Pike were included regardless of the time between captures. Furthermore, additional Northern Pike capture records from other UCRB studies, such as Colorado Pikeminnow abundance estimate sampling (Bestgen et al. 2007a(Bestgen et al. , 2010aOsmundson and White 2014) and fish community monitoring downstream of Flaming Gorge Dam on the Green River (Bestgen et al. 2010b), were included. Direction and distance traveled (km), elapsed time (d) between capture and recapture, reach changes, reservoir escapement, and recaptures after translocation were documented for each recapture event. ...
The Northern Pike Esox lucius is invasive in the upper Green and Yampa River basins of Colorado and Utah and impedes endangered fish recovery in the upper Colorado River basin. Mechanical removal was implemented in 2004, but Northern Pike population dynamics and removal efficacy were not well understood. We analyzed mark?recapture records from 8,929 individual Northern Pike captured during 2004?2010 from three reaches of the Yampa River: Hayden to Craig (upstream reach), South Beach?Little Yampa Canyon?Juniper (middle reach), and Maybell?Sunbeam (downstream reach), encompassing 175 river kilometers. Annual survival rates for Northern Pike of the mean TL (465 mm) were highest downstream (mean = 0.54; range = 0.36?0.71) and lowest upstream (mean = 0.25; range = 0.12?0.38). Annual abundance exhibited the opposite pattern, as it was highest upstream (annual range = 1,144?4,078 fish) and lowest downstream (range = 232?746 fish). After removal occurred each year, Northern Pike abundance increased annually by nearly 1,000% in the upstream reach, over 875% in the middle reach, and over 375% in the downstream reach due to recruitment and immigration. Resulting densities were 4?58 times higher than those for a native apex predator, the endangered Colorado Pikeminnow Ptychocheilus lucius. Northern Pike movement was mostly (90%) downstream and sometimes extensive, which may have promoted establishment of additional populations. Removal rates were inadequate to reduce Northern Pike abundance in the Yampa River because recruitment and immigration exceeded removal and mortality. Investigation of reproduction and recruitment, along with source management, spawning disruption, and increased removal, are needed to further reduce Northern Pike abundance and to aid recovery of native and endangered fishes. These findings underscore the need for sustained, comprehensive, and often costly removal efforts?including evaluation of their effects?in the face of the expanding distribution and abundance of invasive predator species.
Received April 16, 2015; accepted March 29, 2016
... Thus, factors that regulate distribution, abundance, size-structure, and survival of early life stages are integrated into processes that structure recruitment (Thorson 1950; Gaines et al. 1985; Houde 1987; Miller et al. 1988; Underwood and Fairweather 1989; Johnston et al. 1995). Life history patterns and populations of Colorado pikeminnow of the Colorado River basin (Figure 1) are consistent with multi-phase life cycle characteristics because each life stage disperses widely and patterns of survival and recruitment vary within and among years (Tyus 1991; Osmundson and Burnham 1998; Bestgen et al. 2006; Bestgen et al. 2007a; Bestgen et al. 2010; Osmundson and White 2014). In the Green River (Figure 2), where the largest remaining naturally reproducing Colorado pikeminnow population occurs, the two main spawning areas are in the downstream portion of the Yampa River, and the lower Green River in Gray Canyon. ...
... northern pike captures resulted from targeted non-native species removal efforts and from other UCRB studies where fishes were captured, such as Colorado pikeminnow abundance estimate sampling (Bestgen et al. 2010a; Osmundson and White 2014) and fish community monitoring downstream of Flaming Gorge Dam on the Green River (Bestgen et al. 2010b). northern pike were captured by boat, raft, and backpack electrofishing; " block-and-shock " sampling (closing off large backwater mouths with trammel nets while electrofishing); seining; electric seining; gill, fyke, and trammel netting; and angling. ...
... As a result of differences in habitat and fish communities, the upper Colorado River basin is considered the last stronghold for several large river fishes native to the Colorado River basin. For example, wild populations of Colorado pikeminnow persist in the Green River and Colorado River subbasins and some larger tributaries, including the Yampa River (Bestgen et al. 2007a;Osmundson and White 2014). Colorado pikeminnow is also found in the San Juan River but population augmentation by stocking hatchery-reared individuals is necessary to maintain it there (Platania et al. 1989;Franssen and Durst 2014). ...
... For example, about 900 RK of mainstem and tributary habitat in the Green River subbasin is occupied by Colorado pikeminnow. In contrast, Colorado pikeminnow in the mainstem Colorado River occupy only about 322 RK (Osmundson and Burnham 1998;Osmundson et al. 1997;Osmundson and White 2014). Populations of Colorado pikeminnow in the San Juan River, about 282 RK long, are present mainly as stocked individuals with only modest documented recruitment to the adult life stage (Platania et al. 1989;Holden 1999;). ...
Executive Summary
Maintaining various components of the natural flow regime of the Yampa River is essential to create habitat and preserve the native and endangered fishes it supports. Further, the Yampa River provides the downstream Green River with a more natural flow and water temperature pattern, and creates essential connections between the river and floodplain wetlands so native fishes can benefit. This report describes those essential components of the Yampa River flow regime, recognizing that all elements of the flow regime are important and losses or alterations would negatively affect ecosystem integrity. The following statements are excerpted from summary paragraphs located at the end of this report, with the corresponding topical section headers presented in bold. Information presented in this report is based on existing literature, data, and professional opinion, regarding aspects of the Yampa River flow regime thought essential for preservation of native fishes. A full reading of the report is encouraged so the reader understands the context under which these statements were developed.
Maintain the natural flow patterns of the Yampa River
• An optimal Yampa River flow regime would maintain the natural regime of the Yampa River in its entirety.
• Maintaining peak flows and enhancing base flows from present reduced levels would support many processes in the life history of native fishes, including providing spawning cues, physical habitat creation, and substrate cleansing.
• Maintenance of natural flows and relatively high peak and base flows will also promote reproduction and survival of native fishes, and reduce reproduction and abundance of most nonnative fishes.
Maintain peak flows
• Peak flows provide important physical habitat maintenance functions in the Yampa River including sediment transport from the stream channel, substrate mobilization for spawning habitat formation and maintenance, and sand transport and deposition for secondary channel and backwater formation.
• High flows may also provide a signal for fishes to prepare for or begin reproduction.
• High flows on floodplain surfaces or in tributary mouths provide relatively warm and low velocity off-channel habitat where fishes can increase body condition when Yampa River flows are high and cold.
• Peak Yampa River flows also provide amplitude and volume to spring flows in the downstream Green River. Those flows rejuvenate physical habitat, provide that regulated system with a more natural hydrograph shape and pattern, and connect the river with the extensive floodplain.
• Floodplain connections in the Yampa River and especially the downstream Green River are important for adult life stages of bonytail, Colorado pikeminnow, and razorback sucker as well as early life stages of razorback sucker because wetlands are warm and food rich relative to the cold and relatively unproductive main channel.
Maintain or enhance base flows, especially in late summer
• Base flows are, at present, the most altered aspect of the Yampa River hydrograph and based on one-day annual low flows have declined by 37% from 1922-2013. Low base flows reduce riffle habitat depth and area and reduce food and habitat availability.
• Riffles are important food production and foraging areas for all native fishes, and are also important for fish passage because large-bodied native fishes must traverse riffles to move throughout the Yampa River.
• Base flows also provide important habitat for early life stages of native fishes in nearshore areas, such as backwaters and secondary channels, including in the Green River.
• Higher base flow levels may also provide a thermal regime that is more favorable overall for the native fish community as a result of reducing nonnative predator fish growth, particularly for smallmouth bass.
Maintain post-peak, descending limb flows
• Descending limb Yampa River flows are important because that is when most native fishes reproduce.
• Increasing warming rates via descending limb flow reductions may disrupt adaptations for reproductive isolation and spawning chronology of native fishes and increase hybridization of native suckers with nonnative white sucker in the Yampa and Green rivers.
• Descending limb flows provide main-channel spawning fishes with clean gravel riffles for egg deposition, and sweep away fine sediments to maintain interstitial water flow, which is important for successful development of embryos and larvae over relatively long post-spawning periods of native fishes.
• Increasing the rate of warming during descending limb flows in spring by reducing flow volumes will also promote earlier spawning and faster growth of deleterious nonnative fishes such as smallmouth bass and small-bodied nonnative cyprinids.
Maintain as much of ascending limb flows as possible
• Flow alterations and water diversion from the Yampa River during the ascending limb of the hydrograph may be least damaging to the fishes and their habitat than any other time of year.
• Ascending limb flows of the spring hydrograph may also play a role in signaling timing for reproduction by native fishes, including in the downstream Green River.
• Increasing warming rates via flow reductions on the ascending limb of the hydrograph may disrupt adaptations for reproductive isolation and spawning chronology of native fishes and increase hybridization of native suckers with nonnative white sucker.
• Flow reductions during the ascending limb of the Yampa River hydrograph may increase water temperatures of the Yampa River. However, the potential for impacts to temperature signals for fishes in early spring, from ascending limb flow reductions in the Yampa River, seems relatively low if base flow or higher flow levels are maintained during that relatively cool season.
• Sediment transport occurs on the ascending, peak, and descending limbs of the hydrograph in the Yampa and Green River systems and early season transport capacity may be reduced.
• It is uncertain if some ascending limb flows were removed, if sufficient flows for sediment transport would be available during pre-peak and peak flow periods for clearing and rejuvenation of substrate in spawning areas.
Minimize short-duration flow fluctuations
• Minimize short-term and frequent flow releases that elevate river stage and discharge that can be disruptive to fish communities, especially if early life history stages of fish are present. Infrequent fluctuations to disrupt reproductive success of invasive species may be beneficial.
• Minimize base flow fluctuations in winter that may disrupt habitat stability and create potentially stressful conditions that reduce energy reserves and potentially survival of fish.
• Formation of ice cover provides a relatively stable riverine environment so flow fluctuations or base level increases that break ice cover should be avoided.
Maintain water temperature regimes
• The stream fish community in the Yampa River downstream of Craig, Colorado requires a summer-warm thermal regime that should be maintained.
• High water temperatures in the Yampa River are not deleterious to native fishes, but they also increase smallmouth bass growth rates, and subsequently, bass predation pressure on native fishes.
• Water temperature increases to very high levels in flow-depleted systems should be avoided.
Frequency and timing of recommended flow patterns
• Flow patterns recommended for peak, ascending limb, descending limb, and base flows need to continue in perpetuity.
• It is recognized that flow volumes will vary year to year based on snowpack and other hydrologic conditions, and that more geomorphic work may be completed in higher flow years than others.
• The timing of flow events should be largely dictated by the natural hydrograph.
Maintain natural peak flow durations
• Peak flows perform useful geomorphic work and create important fish habitat but the duration of peak flows needed to perform physical habitat formation and maintenance is less certain.
• The natural hydrograph will dictate much in terms of peak duration, which will typically be longer in higher flow years, and shorter in lower flow years.
• Accurate predictions of the onset of the three peak flow segments, ascending, peak, and descending portions, are needed to maintain the most valuable functions of flows in the Yampa River and the downstream Green River.
Maintain turbidity patterns
• Water turbidity, caused by suspension of fine clay particles in the water column, is a natural part of Yampa River flows.
• The interplay of turbidity on predation and growth and survival of native fishes may be important to understand the ecology of native and nonnative fish interactions in the Yampa and Green rivers.
Maintain or increase nonnative fish management efforts to reduce long-term effects
• Nonnative fishes, especially large-bodied piscivorous species such as smallmouth bass and northern pike, have the potential to undo many flow management activities undertaken for the benefit of native fishes in the Yampa River system.
• Nonnative fish removal effects are short-term because occasional flow events create large year-classes of various nonnative fishes that are apparent for several years in the river, and require several years of mechanical removal effort to suppress. Also, flow patterns do not affect nonnative fishes in similar ways.
• The specter of additional introductions and establishment of other species is real and ongoing as new species invade the system on a regular basis. This is sobering given that already established nonnative fishes are widespread and abundant, difficult to control, and have documented negative effects on native fishes.
• Ongoing management activities should be supported, with the view towards long-term solutions including controlling source populations, and more effective mechanical control techniques where and when populations are most susceptible.
• It is also important to keep a longitudinal perspective when considering present and future issues with nonnative fishes. This is because the lower Yampa River is positioned between upstream and downstream of river segments that differ with respect to problematic fish
species and because fishes are mobile, with distributions and abundances shifting with environmental regimes and the state (early or late) of ongoing invasions.
Maintain or enhance flow and other management efforts in the Green River to aid the Yampa River fish community
• The co-dependency of Yampa River and Green River processes and fish communities is evident and strong.
• Processes that maintain or strengthen the co-dependency of the systems should be fostered, but are incompletely known.
• A relevant example is the interplay of the higher and later flow releases from Flaming Gorge Dam to promote connections of the Green River with the Uintah Basin floodplain for recruitment of young razorback suckers. Yampa River flows are an integral part of that process, especially the peak and descending limb flows and, as such, should be maintained.
Colorado Pikeminnow Ptychocheilus lucius, the Colorado River’s top native predatory fish, was historically distributed from the Gulf of California delta to the upper reaches of the Green, Colorado, and San Juan rivers in the Colorado River basin in the Southwestern US. In recent decades Colorado Pikeminnow population abundance has declined, primarily due to predation by warmwater nonnative fish and habitat modification following dam construction. Small, reproducing populations remain in the Green and upper Colorado rivers, but their current population trajectory is declining and the San Juan River population is maintained primarily through stocking. As such, establishment of an additional population could aid recovery efforts and increase the species’ resilience and population redundancy. The Colorado River in Grand Canyon once supported Colorado Pikeminnow, but until recently habitat suitability in this altered reach was considered low due to a depressed thermal regime and abundant nonnative predators. Climate change and ongoing drought has presented an opportunity to evaluate the feasibility of native fish restoration in a system where declining reservoir storage has led to warmer releases and re-emergence of riverine habitat. These changes in the physical attributes of the river have occurred in concert with a system-wide decline in nonnative predators. Conditions ten years ago were not compatible with reintroduction feasibility in Grand Canyon; however, due to rapidly changing conditions an expert Science Panel was convened to evaluate whether the physical and biological attributes of this reach could now support various life stages of Colorado Pikeminnow. Here, we report on the evaluation process and outcome from the Science Panel, which developed a science-based recommendation to the U.S. Fish and Wildlife Service on reintroduction feasibility. The Science Panel concluded that current habitat attributes in Grand Canyon could satisfy some, but perhaps not all, Colorado Pikeminnow life history requirements. This reach has the potential to support adult and sub-adult growth, foraging, migrations, and spawning, but low juvenile survival may limit recruitment. However, populations of other native species are successfully reproducing and increasing in western Grand Canyon, even in areas once considered suboptimal habitat. Should managers decide to move to the next phase of this process, actions such as experimental stocking and monitoring, telemetry studies, bioenergetics modeling, and laboratory-based research may provide additional information to further evaluate a potential reintroduction effort in this rapidly changing but highly altered system.
This chapter describes the geomorphic and hydrologic attributes of the Colorado river, the changes that have occurred in these attributes during the past ~150 years, the relationship of these attributes to the dependent ecological and human systems, and the efforts made to reverse undesired environmental trends. Bursztyn et al. showed a strong correlation between rock hardness and gradient for the Green and main stem Colorado Rivers across the Rocky Mountains and Colorado Plateau. The hydrology of the lower Colorado River was fundamentally changed by construction of Hoover Dam that formed Lake Mead. Pre‐dam resources include attributes of the pre‐dam riparian and aquatic ecosystem and the flow and sediment transport conditions in which those ecosystems developed. Several environmental management programs have been created in response to the social pressures and legal requirements to protect and recover endangered fish or restore attributes of the pre‐dam riverine ecosystem.
