561 items found

Led ByJake Ivan

Study AreaStatewide

Project StatusOngoing

Research Objectives

• To evaluate options to monitor the long-term success of lynx reintroduction efforts.

Project Description

In 1997, Colorado Parks and Wildlife began a large-scale effort to reintroduce lynx into the state with the goal of establishing a self-sustaining population of lynx. Four years after the last lynx was released into the state in 2006, CPW deemed the initial lynx introduction effort a success. Research focus has now shifted towards determining the long-term success of the reintroduction. 

Researchers cannot use traditional methods to estimate abundance of lynx populations because the animals move extensively, exist at low densities, and can be difficult to capture. Instead, this project aims to monitor lynx population trends by using presence/absence data to estimate the proportion of the landscape occupied by lynx.  This proportion should trend up or down as lynx abundance moves up or down.

From 2009 to 2010, researchers tried various methods of detecting lynx in areas where they were known to be present. This work showed that snowtracking surveys conducted by snowmobile were the most efficient means to detect lynx. However, such surveys can only occur in roaded areas. For surveys in wilderness areas, researchers determined that remotely triggered wildlife cameras were the most efficient method for detecting lynx. 

Based on data collected from field research in 2009-2010, researchers determined that a sample of 50 sample units would need to be surveyed annually in the San Juan and South San Juan Mountains in order to be able to detect meaningful trends in lynx occupancy in the region. 

Work will be completed by CPW in partnership with the U.S. Forest Service. Additionally, other ranges throughout the state will be surveyed on a rotating basis such that when the monitoring effort is at full strength, annual data will be collected in the Southwest to monitor trends in the population, and periodic surveys will be conducted elsewhere to determine the extent of the population in the state.  

Associated Publications

• Ivan, J. S., 2013. Statewide Monitoring of Canada lynx in Colorado: Evaluation of options. Pages 15-27 in Wildlife Research Report, Mammals Research Program, Colorado Division of Parks and Wildlife, Fort Collins, CO. 310 pp.
• Ivan, J. S., 2012. Monitoring Canada Lynx in Colorado Using Occupancy Estimation: Initial Implementation in the Core Lynx Research Area. Pages 26-34 in Wildlife Research Report, Mammals Research Program, Colorado Division of Parks and Wildlife, Fort Collins, CO. 195 pp.
• Ivan, J.S., 2011. Monitoring Canada Lynx in Colorado Using Occupancy Estimation: Initial Implementation in the Core Lynx Research Area. Wildlife Research Report, Mammals Research program, Colorado Division of Parks and Wildlife, Fort Collins, CO.

Led By

​Dr. George J. Schisler​

Study Area

Parvin Lake, Red Feather Lakes, CO​

Project Status

Led ByHeather Johnson, Matt Hammond, Patt Dorsey, Kurt VerCauteren (USDA National Wildlife Research Center), Justin Fischer (USDA National Wildlife Research Center), W. David Walter (USDA National Wildlife Research Center), and Charles Anderson (USDA National Wildlife Research Center).

Study AreaVicinity of Dove Creek, Colorado 

Project StatusCompleted

Research Objectives

• To test various non-lethal techniques to reduce elk and deer crop depredation.
• To examine elk and mule deer distribution and migration patterns around agricultural areas to design public hunting opportunities to reduce crop damage.
• To map and model landscape characteristics associated with elk and deer damage to identify site-specific management strategies to minimize crop depredation.

Project Description

Elk and mule deer provide important recreational, ecological, and economic benefits, but they can also cause substantial damage to crops in rural areas. Crop damage caused by elk and deer accounts for a majority of the state's wildlife damage claims, which Colorado Parks and Wildlife is obligated to pay.

In particular, the sunflower fields around Dove Creek have experienced high rates of damage from elk and deer. Between 2007 and 2009, CPW paid farmers in the region roughly a quarter of a million dollars annually and routinely allocated kill permits, distribution hunts and private land only doe/cow hunts to eliminate animals causing damage. Pressure from local growers over crop damage and frustration from the general public over kill permits prompted CPW to evaluate other management options for reducing crop damage caused by elk and deer. 

As a result, CPW partnered with wildlife damage researchers from the USDA National Wildlife Research Center to test various non-lethal solutions to reduce crop damage. Such techniques include polyrope electric fencing, winged fencing, and an organic repellent. In addition, researchers are tracking deer and elk movement patterns using GPS collars. The data will be used to identify distribution and migration patterns so that public hunts can be designed that target those elk and deer causing conflicts with farmers. In addition, deer and elk location data will be used to model damage potential in relation to field locations, surrounding habitat types, human development, and topography. Information about the location of a crop field in the context of the overall landscape will allow CPW to work with local growers to identify appropriate management strategies to reduce game damage.

Results from this study should enable CPW and local growers to reduce deer and elk crop depredation, leading to a decrease in compensation payments, a decrease in kill permits/distribution hunts, and an increase in public hunting opportunities.

Associated Publications

Led By

Lake and Reservoir Researchers

Study Area

Select reservoirs

Project Status

Ongoing

Research Objectives

• Examine the suitability of specialized gill netting protocols for assessing sport fish populations in key Colorado reservoirs.

Project Description

Gill nets are commonly used to monitor fish populations. They are lightweight, easy to use, catch multiple sizes and species of fish simultaneously, and provide information (i.e., numbers and sizes) that can be compared through time. Observed trends in catch information from annual gill net surveys are used to inform fisheries management decisions.

The Lake and Reservoir Research group has been investigating the appropriateness of specialized gill netting protocols developed by the Ontario Ministry of Natural Resources that enable biologists to estimate the total number of fish in a lake or reservoir (i.e., “abundance”). Specifically, lake trout and walleye, which are two highly sought sport fish in Colorado.

Researchers have examined two protocols: Summer Profundal Index Netting (SPIN) for lake trout, and Fall Walleye Index Netting (FWIN) for walleye. Both protocols use gill nets set for a defined duration at multiple depths across all regions of a reservoir, resulting in a rapid, comprehensive survey typically completed over 2-4 days.

Other methods for estimating the abundance of a fish population (like tagging and then recapturing tagged fish) in a lake or reservoir are resource intensive, and can be cost prohibitive. Thus, techniques such as SPIN and FWIN can be valuable when in-depth population assessments are needed to help inform complex management decisions. For example, changes to harvest regulations, how to balance top predators with their prey fish populations, or other challenges managers face.

Associated Publications

Beauchamp, D.A., A.G. Hansen, and D.L. Parrish. 2024. Chapter 7: Coldwater fish in large standing waters. In Standard methods for sampling North American freshwater fishes (2^nd edition). Edited by S.A. Bonar, W.A. Hubert, and D.W. Willis. American Fisheries Society, Bethesda, Maryland.

Hansen, A.G. 2019. Size-dependent retention of pelagic-oriented kokanee in multimesh gill nets. North American Journal of Fisheries Management 39:921-932.

Hansen, A.G., M.W. Miller, E.T. Cristan, C.J. Farrell, P. Winkle, M.M. Brandt, K.D. Battige, and J.M. Lepak. 2023. Gill net catchability of walleye (Sander vitreus): are provincial standards suitable for estimating adult density outside the region? Fisheries Research 266:106800.

Pate, W.M., B.M. Johnson, J.M. Lepak, and D. Brauch. 2014. Managing for coexistence of kokanee and trophy lake trout in a montane reservoir. North American Journal of Fisheries Management 34:908-922.

Led By

Lake and Reservoir Researchers

Study Area

Select lakes and reservoirs

Project Status

Ongoing

Research Objectives

• Evaluate the relative influence of different physical and biological factors on the post-stocking performance of sterile hybrid predators and responses by undesirable or overabundant prey fishes to inform best stocking practices.

Project Description

Hybrid predators such as tiger muskellunge (cross between northern pike and muskellunge) and tiger trout (cross between brook trout and brown trout) are sterile (cannot reproduce) and often stocked to control undesirable or overabundant prey fish species (e.g., suckers) that compete with other valuable sport fish such as rainbow trout and cutthroat trout. Because these hybrids are sterile, managers can keep close tabs on their numbers, and predatory or competitive effects only last over their lifespan. Hybrid predators also provide unique angling opportunities and have the potential to reach trophy sizes.

The ability of hybrid predators to control unwanted or overabundant fishes while providing quality angling opportunities depends on many factors related to the physical and biological attributes of a lake or reservoir.

The Lake and Reservoir Research group has been quantifying the effects of different factors on the post-stocking performance (feeding, growth, survival and responses by prey fish populations) of hybrid predators to inform best stocking practices. Informed stocking translates into the efficient use of the limited number of hybrid predators produced by CPW’s hatchery system, a greater chance of achieving desired outcomes, and more rapid development of quality fishing opportunities for Colorado’s anglers.

Tiger trout research highlight:

A recent study on juvenile tiger trout stocked into subalpine lakes found that growth early in life was sensitive to the numbers of tiger trout stocked; the higher the density, the slower their growth. The study also found that when undesirable prey fishes were numerous and large, tiger trout did not grow as well, and the same was true when other trout species were being stocked simultaneously.

Enhanced growth early in life is linked to improved survival and the ability of juvenile predators to transition to eating larger-bodied prey fish sooner. Results from this study suggest that stocking practices (numbers, sizes and frequency) designed to enhance growth early in life or bypass potential growth bottlenecks may improve the ability of tiger trout to meet multiple fisheries management objectives over the long-term. Information provided in this study helps guide managers in this process.

Tiger muskellunge research highlight:

Tiger muskellunge are a valuable management tool, and a focus for CPW researchers. Tiger muskellunge have been stocked in more than 100 lakes and reservoirs in Colorado since 1983. Similar to tiger trout, tiger muskellunge are stocked to control nuisance or overpopulated fish species. However, tiger muskellunge can achieve large sizes (the Colorado record is over 40 pounds), and can be effective at controlling relatively large nuisance fish species (like white suckers).

With over 100 places to learn from, researchers have an opportunity to use historical survey data collected by CPW biologists to understand where stocking tiger muskellunge has had the desired effects (reducing the number of undesirable fish species), and where stocking has not met management objectives. Researchers can also look at other aspects of different lakes and reservoirs like the forage available, trout stocking, and the presence of competitors (like northern pike) to determine if those factors influence the post-stocking performance of tiger muskellunge.

Previous CPW research combined with the historical data analysis completed thus far, has shown that when tiger muskellunge are large enough, they tend to consume catchable trout when they are available. This means that the impact tiger muskellunge have on undesirable fish species is reduced or buffered against when trout are stocked because they are consumed before the intended species. If the weight of trout stocked in a particular lake or reservoir is enough to feed the tiger muskellunge present, their effect on undesirable species will be highly diminished or absent. Understanding these kinds of variables and looking further into historical data will allow CPW researchers to develop stocking formulas for tiger muskellunge (how many and how often) to increase their post-stocking performance and their success at achieving intended management goals.   

Associated Publications

Hansen, A.G., E.T. Cristan, M.M. Moll, M.W. Miller, E.I. Gardunio, and J.M. Lepak. 2022. Factors influencing early growth of juvenile tiger trout stocked into subalpine lakes as biocontrol and to enhance recreational angling. Fishes 7:342.

Lepak, J.M., C.N. Cathcart, and W.L. Stacy. 2014. Tiger muskellunge predation upon stocked sport fish intended for recreational fisheries. Lake and Reservoir Management 30:250-257.

Lepak, J.M., E.R. Fetherman, W.M. Pate, C.D. Craft, and E.I. Gardunio. 2012. An experimental approach to determine esocid prey preference in replicated pond systems. Lake and Reservoir Management 28:224-231.

Led By

​Dr. Eric R. Fether​man​

Study Area

Colorado River, Poudre River, and South Platte River Drainages​

Led By

Lake and Reservoir Researchers

Study Area

Select reservoirs

Project Status

Ongoing

Research Objectives

• Monitor the response of target fishes to incentivized angling.
• Monitor the participation and harvest dynamics of anglers.
• Develop population models and other quantitative tools to inform the biological effectiveness of ongoing incentivized angling efforts.

Project Description

CPW strives to provide the best sport fishing opportunities that are appropriate for each water body in the state of Colorado. Opportunities in some locations may not be appropriate for others given differences in management objectives, the need to protect native fish species in sensitive locations, the need to maintain wild broodstocks that provide valuable eggs to the states hatchery system, or other ecological factors. 

One example is the presence of nonnative predatory sport fish like smallmouth bass and northern pike stocked historically or illegally into some reservoirs on the western slope of Colorado that are located upstream of critical river and stream habitats for unique native fishes. The presence of these predatory fish undermines conservation efforts because they can escape the reservoirs, establish populations downstream, and eat or compete with native fish.

One of CPW’s missions is to protect native species that represent the ecology and natural history of the state. Sometimes, management actions to limit nonnative predatory sport fish in unwanted locations is necessary. Therefore, CPW has been implementing fishing tournaments in locations like Ridgway (southwest Colorado) and Elkhead (northwest Colorado) reservoirs where anglers can win cash prizes by helping CPW remove unwanted predatory fishes from the reservoirs to favor more compatible sport fish species.    

Harvest of sport fish is also sometimes needed for reasons other than native fish protection. For example, the need to maintain predator-prey balance in systems like Blue Mesa Reservoir (southwest Colorado) where consumption of stocked kokanee salmon by naturally reproducing lake trout can become unsustainable. Here, periodic harvest incentives are used to remove overabundant small lake trout (greatest predation impact on juvenile kokanee based on previous research) to help maintain the adult kokanee population where needed for egg-collection purposes and to maintain angling opportunities for trophy (even world record) lake trout.

In both contexts, Lake and Reservoir Researchers have been working alongside managers collecting additional biological information and developing quantitative survey or modeling tools to inform the effectiveness of these angler incentive programs, identify potential avenues for increasing effectiveness if necessary, and to enable adaptive decision making.              

Associated Publications

Cristan, E.T. 2021. Angler incentives: lucrative lake trout in Blue Mesa Reservoir. Colorado Outdoors Magazine. September/October Issue, Vol. 70, No. 5.

Hansen, A.G., J.M. Lepak, E.I. Gardunio, and T. Eyre. 2024. Evaluating harvest incentives for suppressing a socially-valued, but ecologically-detrimental, invasive fish predator. Fisheries Management and Ecology 31:e12699.

Pate, W.M., B.M. Johnson, J.M. Lepak, and D. Brauch. 2014. Managing for coexistence of kokanee and trophy lake trout in a montane reservoir. North American Journal of Fisheries Management 34:908-922.

Led By

Kevin Tho​mpson​, Jenn Logan

Study Area

Colorado River Basin

Project Status

Ongoing

Research Objectives

• To characterize Colorado-wide genetic diversity and purity among native sucker populations.
• To ensure proper geographic representation of each species of sucker in brood stocks at CPW's Native Aquatic Species Restoration Facility (NASRF) in Alamosa.
• To determine whether CPW researchers and biologists are encountering hybrid suckers that appear pure and to gauge accuracy in identifying which parental species are involved in hybrid specimens.

Photos:Top right: Mouth of Pure Bluehead SuckerBottom right: Mouth of Bluehead/White Sucker Hybrid

​Project Description

Flannelmouth and bluehead sucker populations have declined in recent years, prompting CPW to focus efforts towards protecting and enhancing existing populations of these ecologically important fishes. Both flannelmouth and bluehead suckers will hybridize with non-native sucker species introduced to the Western Slope, threatening the genetic purity of the natives. To combat this problem or to re-establish populations of the native suckers, CPW needs to prepare for the use of captive-reared fish, necessitating the establishment of one or more brood stocks for each species.

Therefore, CPW initiated a study to characterize the genetic purity and diversity of suckers from river drainages across Colorado. To do so, researchers and biologists collected genetic samples from pure suckers to establish reference populations with which future genetic specimens could be compared. Afterwards, hundreds more samples were collected from numerous locations around the Western Slope to assess which populations remain the purest and also to determine how genetically diverse the various populations are. Results from this study helped determine how many brood stocks of each species CPW should maintain at NASRF in order to appropriately represent the genetic diversity of wild populations.

At the time of sampling, collectors attempted to visually identify the species of each sucker and several photographs were taken. Some fish of each species and each hybrid combination were retained as specimens for archiving and future study, as well as for future training in identification. Each genetic sample was analyzed and assigned to species or species mixes for hybrids. Genetic identifications were then compared to field identifications to assess agreement.  ​

We discovered that biologists and researchers were quite accurate in identifying pure fish versus hy​brid fish; however, identification of which parental species were represented in hybrid fish was very challenging especially when more than two ancestral species were represented in hybrid fish.

​Video: Bluehead Sucker Spawning​

Led ByJedediah Brodie, Heather ​Johnson (CPW), Michael Mitchell, Peter Zager, Kelly Proffitt, Mark Hebblewhite, Matthew Kauffman, Bruce Johnson, John Bissonette, Chad Bishop (CPW), Justin Gude, Jeff Herbert, Kent Hersey, Mark Hurley, Paul Lukacs, Scott McCorquodale, Eliot McIntire, Josh Nowak, Hall Sawyer, Douglas Smith and P.J. White

Study AreaWestern North America

Project StatusCompleted

Research Objectives

• To determine the relative influence of predation, weather, habitat, land-use and harvest on adult female elk survival.

Project Description

The challenges facing elk management in western landscapes are increasing at a rapid pace as changes to habitat, climate and predator communities influence elk population demography and behavior.

In an effort to understand these new challenges and effectively manage elk in the future, researchers across seven states in western North America began to communicate about shared management challenges and research needs. Collaborators decided that a region-wide study across all the states would provide managers a big-picture view of how broad-scale drivers are influencing elk populations.

Therefore, CPW collaborated with state and federal wildlife agencies in Montana, Idaho, Wyoming, Washington, Oregon and Utah to investigate large-scale temporal and spatial patterns in adult female elk survival and cause-specific mortality. 

Results from this study will help wildlife managers better respond to changing environmental conditions in the future.

Collaborators for this project include personnel from the USGS Montana Wildlife Cooperative Research Unit, USGS Wildlife Cooperative Research Unit, USGS Wyoming Cooperative Research Unit, Idaho Fish and Game, Montana Fish, Wildlife and Parks, Oregon Department of Fish and Wildlife, Washington Department of Fish and Wildlife, Utah Division of Wildlife Resources, Wyoming Game and Fish Department, and Yellowstone National Park.

Associated Publications

Brodie, J., H. Johnson, M. Mitchell, P. Zager, K. Proffitt, M. Hebblewhite, M. Kauffman, B. Johnson, J. Bissonette, C. Bishop, J. Gude, K. Hersey, M. Hurley, P. Lukacs, S. McCorquodale, E. McIntire, J. Nowak, D. Smith, and P.J. White. 2013. Relative influence of human harvest, carnivores, and weather on adult female elk survival across western North America. Journal of Applied Ecology 50:295-305.