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ID: Evaluation of an Electric Fish Barrier on the South Canal, an Irrigation Ditch on the Lower Gunnison River, Colorado
Evaluation of an Electric Fish Barrier on the South Canal, an Irrigation Ditch on the Lower Gunnison River, Colorado
Type: 
Subjects: 
Item 

        Evaluation of an Electric Fish Barrier on the South Canal, an Irrigation Ditch on the Lower Gunnison River, Colorado    

                    Description:Led By
Dan Kowalski​​
Study Area
South Canal of the Gunnison River
Project Status
Complete
Research Objectives
To monitor fish population trends in the canal and evaluate the effectiveness of an electric fish barrier in reducing fish entrainment through a marked fish study
Project Description
There are over 105,000 irrigation structures on rivers and streams across Colorado, most in fish-bearing waters.  Fish entrainment in irrigation canals is known to be a large problem in the western U.S. but its impact on fish populations in Colorado is unknown.  The South Canal, an irrigation ditch in southwest Colorado, diverts about 360,000 acre feet of water each year (around 1,000 cfs per day) from the Gunnison River into the Uncompahgre Valley for agricultural irrigation use.  With the construction of several new hydropower plants on the canal in 2012, CPW expected to see an increase in fish mortality and impacts to recreational fishing in the South Canal and Uncompahgre River.
In order to reduce impacts on the Gunnison River's Gold Medal trout fishery, an electric fish barrier was installed at the east portal of the canal. Consisting of a series of vertically suspended electrodes, the system aims to discourage brood stock fish from entering the canal and potentially dying in the hydropower turbines.
CPW initiated a study to compare fish populations in the canal before and after the barrier was built and to document fish movement across the barrier with tagged fish. 
Study results revealed that some fish passed through the barrier and survived the turbines, with more small fish successfully passing than large fish. Fish population estimates in the canal have declined after the electric barrier, but not significantly at the 95% level. A total of 288 tagged fish less than 12 inches and four fish greater than 12 inches were recovered below the barrier.  No fish greater than 16 inches have been documented crossing the barrier.  Only 1.3% of all tagged fish were documented to have been entrained in the canal while the barrier was operating. 
The electric barrier appears to successfully exclude larger fish from the study reach, but not age 1 and age 0 trout. The electric fish barrier is successful in its stated objective, but not in reducing overall fish densities in the canal because the growth and survival of smaller fish maintains a stable population of fish in the canal. Reducing the entrainment of large fish is likely a benefit to the trout population of the Gunnison River. Further study is needed to evaluate if smaller trout can be successfully excluded by the electric barrier.
Associated Publication
Evaluation of an Electric Fish Barrier on the South Canal, an Irrigation Ditch on the Lower Gunnison River, Colorado 
Fact Sheet: Electric Fish Barrier Research
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ID: Evaluation of an electric fish barrier on the South Canal, an irrigation ditch on the lower Gunnison River, Colorado
Evaluation of an electric fish barrier on the South Canal, an irrigation ditch on the lower Gunnison River, Colorado
Type: Text
Subjects: Sport fish
Fishing
South canal
Research
Item 

        Evaluation of an electric fish barrier on the South Canal, an irrigation ditch on the lower Gunnison River, Colorado    
Type:Text
Subject:Sport fish
Fishing
South canal
Research

                    Description:An electric fish barrier was installed on the east portal of South Canal to reduce fish entrainment associated with the construction of two hydropower plants in 2012. The objective of this study was to monitor fish entrainment and evaluate the effectiveness of the barrier. Three groups of fish were tagged and released upstream of the barrier; fish from the canal, wild Gunnison River fish, and hatchery reared fingerlings. Mark recapture boat electrofishing was completed and population estimates were made with the Huggins Closed Capture model using fish length to model capture probabilities. The study reach contained 2,994 ± 1,043 fish (>150 mm) in October 2011, 1,764 ± 279 in October 2013, 1,224 ± 239 in July 2014 and 1,900 ± 379 in October 2014. Fish population estimates have declined after the electric barrier, significantly at the 95% level for brown trout but not for rainbows. A total of 288 tagged fish less than 300 mm and four fish greater than 300 mm were recovered below the barrier, representing 1.3% of all tagged fish. The electric barrier appears to meet its objective and successfully exclude larger fish from the study reach, but not smaller age 0, age 1, or age 2 trout. The entrainment, growth and survival of smaller fish maintains a stable population of fish in the canal, but fewer entrained mature fish is likely a benefit to the fish population of the Gunnison River. Further study is needed to evaluate if smaller adult trout can be successfully excluded by the electric barrier with operational modifications. [show more]                

ID: Evaluation of Longrie-Fectau fish passage structure
Evaluation of Longrie-Fectau fish passage structure
Type: 
Subjects: Longrie-Fectau fish passage structure
Item 

        Evaluation of Longrie-Fectau fish passage structure    
Subject:Longrie-Fectau fish passage structure

                    Description:Abstract: Connectivity is critical for freshwater fish conservation, and the design of fish passage structures is a tradeoff between the space available for construction, slope, and costs associated with the structure. The Longrie-Fectau fish passage structure was designed to be modular, readily deployable, and site-generic. To accomplish this, it was designed as two prefabricated portions (straight and curved) that can be quickly installed and accommodate various barrier heights by adding or removing sections. Additionally, the length of straight sections can be altered to fit any site. The sinuous passage design allows a relatively low grade (2%) and passage over large structures with short apron space. The individual pre-cast costs were $9,000 for each of the straight sections, and $6,000 for each of the curved sections. The foundation required to support the pre-cast sections was approximately $4,000 per section. Other financial considerations that will vary depending on the site include the passage entrance and exit, the cap to limit sheet flow over the passage, diverting and dewatering the creek during construction, and additional foundation construction to support the pre-cast sections. We evaluated fish passage through this structure in Fountain Creek, Colorado via a PIT tag mark-recapture study. We documented four Great Plains native fish species successfully ascending the passage structure, with most passage occurring at night. We estimated a 3% probability of a released fish encountering the first array, indicating attraction flows are important consideration for passage design. However, once in the structure, there was a high probability of complete passage (89%). Although this particular structure is large (123 m), passage was relatively fast once fish entered, with median time of successful ascent of 19 minutes and fastest successful passage of six minutes. While fish passage often requires site-specific engineering and design, the Longrie-Fectau-style fish passage design is an option that may reduce construction costs due to its modularity and simplicity. [show more]                

ID: Evaluation of techniques to reduce deer and elk damage to agricultural crops
Evaluation of techniques to reduce deer and elk damage to agricultural crops
Type: Article
Subjects: Cervus elaphus nelsoni
Crop damage
Electric fence
Elk
Mule deer
Odocoileus hemionus
Repellent
Sunflowers
Wildlife damage management
Winged fence
Item 

        Evaluation of techniques to reduce deer and elk damage to agricultural crops    
Type:Article
Subject:Cervus elaphus nelsoni
Crop damage
Electric fence
Elk
Mule deer
Odocoileus hemionus
Repellent
Sunflowers
Wildlife damage management
Winged fence

                    Description:Mule deer (Odocoileus hemionus) and Rocky Mountain elk (Cervus elaphus nelsoni) provide important recreational, ecological, and economic benefits, but can also cause substantial damage to agricultural crops. Cervid damage to agriculture creates challenges for wildlife agencies responsible for minimizing crop depredation while maintaining healthy deer and elk populations. Sunflower producers in southwestern Colorado, USA, have experienced high deer and elk damage and were interested in temporary methods to reduce damage that were cost-effective for rotational crops. To address this challenge, we investigated 3 temporary, non-lethal exclusion and repellent techniques for reducing deer and elk damage to sunflowers: 1) a polyrope electric fence, 2) the chemical repellent Plantskydd™, and 3) a winged fence. During July through October 2011 and 2012, we used a randomized block design to test the efficacy of these techniques by quantifying cervid damage to sunflowers and the number of deer and elk tracks traversing treatment and control plot boundaries. Using generalized linear mixed models we found that polyrope electric fences reduced deer and elk damage and presence within plots, while the repellent and winged fences did not reduce ungulate activity. Polyrope electric fences may be a suitable tool in areas where wildlife management agencies want to maintain deer and elk populations but reduce seasonal damage by cervids to high-value crops. In Colorado, use of an effective exclusion technique such as polyrope electric fence could also decrease the need for lethal depredation permits and damage compensation payments, and increase satisfaction among producers and the public. Published 2014. This article is a U.S. Government work and is in the public domain in the USA. [show more]                

ID: Evaluation of translocation of black bears involved in human–bear conflicts in South-central Colorado
Evaluation of translocation of black bears involved in human–bear conflicts in South-central Colorado
Type: Article
Subjects: Black bear
Cause-specific mortality
Colorado
Conflict
Homing
Survival
Translocation
<em>Ursus americanus</em>
Item 

        Evaluation of translocation of black bears involved in human–bear conflicts in South-central Colorado    
Type:Article
Subject:Black bear
Cause-specific mortality
Colorado
Conflict
Homing
Survival
Translocation
<em>Ursus americanus</em>

                    Description:From 1995 to 1997, black bears (Ursus americanus) involved in conflicts with humans in southeastern Colorado, USA, were radiocollared, translocated, and monitored by the Colorado Division of Wildlife to evaluate translocation as a management tool for problem black bears. Specific objectives were to 1) determine postrelease movement patterns of relocated black bears, and 2) estimate cumulative incidence and survival functions. Subadults did not move as far after translocation as adults and less frequently oriented toward the capture site (29% of subad vs. 51% of ad). No subadults returned to the vicinity of capture, whereas 33% of adults did. We used a cause-specific hazards model with a constant age effect across the cause-specific hazards to estimate annual survival rate for translocated adult bears (0.50, 95% credible interval CI = 0.36–0.65) and for subadult bears (0.28, 95% CI = 0.12–0.48). The annual probability of dying due to repeat conflict behavior was slightly lower (0.22 [95% CI = 0.13–0.33] and 0.32 [95% CI = 0.19–0.47]) for adults and subadults, respectively, compared with nonconflict mortalities (0.28 [95% CI = 0.17–0.40] and 0.40 [95% CI = 0.25–0.56]). Based on bears that were not involved in known repeat human–bear conflicts, translocation success was 0.64 (95% CI = 0.49–0.78) and 0.58 (95% CI = 0.42–0.73) for adults and subadults, respectively. Translocation of problem bears had mixed success relative to repeat nuisance activity in Colorado, but should remain a viable management option. Managers should make decisions on the appropriateness of translocation based on the characteristics of the bear, identification of an adequate release site, potential effect of the translocation on the release-site bear population, and other available options. [show more]                

ID: Evaluation of winter range habitat treatments on overwinter survival, density, and body condition of mule deer
Evaluation of winter range habitat treatments on overwinter survival, density, and body condition of mule deer
Type: Text
Subjects: Colorado
Mule deer
Management
Habitat
Item 

        Evaluation of winter range habitat treatments on overwinter survival, density, and body condition of mule deer    
Type:Text
Subject:Colorado
Mule deer
Management
Habitat

                    Description:The management and research of mule deer (Odocoileus hemionus) in Colorado and throughout the Rocky Mountain West is an exciting arena for wildlife professionals as the prevailing view among biologists, managers, researchers, hunters, wildlife viewers and general wildlife enthusiasts is that they would like to see more deer on the landscape. This desire, and the subsequent support it generates for mule deer research, has paved the way for research projects to evolve: each project has generated new data, new knowledge and answers to questions, but each projected has also generated new questions. My research has been a part of this evolution; it benefited from and was built on existing information, it adds new knowledge and hopefully, it will help guide future research. [show more]                

ID: Examination of the interaction between age-specific predation and chronic disease in the Greater Yellowstone Ecosystem
Examination of the interaction between age-specific predation and chronic disease in the Greater Yellowstone Ecosystem
Type: 
Subjects: Demography
Healthy herds
Infectious disease
Matrix model
Prion
Item 

        Examination of the interaction between age-specific predation and chronic disease in the Greater Yellowstone Ecosystem    
Subject:Demography
Healthy herds
Infectious disease
Matrix model
Prion

                    Description:Abstract 
Predators may create healthier prey populations by selectively removing diseased individuals. Predators typically prefer some ages of prey over others, which may, or may not, align with those prey ages that are most likely to be diseased.
The interaction of age-specific infection and predation has not been previously explored and likely has sizable effects on disease dynamics. We hypothesize that predator cleansing effects will be greater when the disease and predation occur in the same prey age groups.
We examine the predator cleansing effect using a model where both vulnerability to predators and pathogen prevalence vary with age. We tailor this model to chronic wasting disease (CWD) in mule deer and elk populations in the Greater Yellowstone Ecosystem, with empirical data from Yellowstone grey wolves and cougars.
Model results suggest that under moderate, yet realistic, predation pressure from cougars and wolves independently, predators may decrease CWD outbreak size substantially and delay the accumulation of symptomatic deer and elk. The magnitude of this effect is driven by the ability of predators to selectively remove late-stage CWD infections that are likely the most responsible for transmission, but this may not be the age class they typically select. Thus, predators that select for infected young adults over uninfected juveniles have a stronger cleansing effect, and these effects are strengthened when transmission rates increase with increasing prey morbidity. There are also trade-offs from a management perspective—that is, increasing predator kill rates can result in opposing forces on prey abundance and CWD prevalence.
Our modelling exploration shows that predators have the potential to reduce prevalence in prey populations when prey age and disease severity are considered, yet the strength of this effect is influenced by predators' selection for demography or body condition. Current CWD management focuses on increasing cervid hunting as the primary management tool, and our results suggest predators may also be a useful tool under certain conditions, but not necessarily without additional impacts on host abundance and demography. Protected areas with predator populations will play a large role in informing the debate over predator impacts on disease
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ID: Experimental evaluation of population trend and harvest composition in a Wyoming cougar population
Experimental evaluation of population trend and harvest composition in a Wyoming cougar population

Type: Article
Subjects: Adaptive management
Cougar
Exploitation
Population trend
<em>Puma concolor</em>
Sex–age composition
Item 

        Experimental evaluation of population trend and harvest composition in a Wyoming cougar population

    
Type:Article
Subject:Adaptive management
Cougar
Exploitation
Population trend
<em>Puma concolor</em>
Sex–age composition

                    Description:Cougar (Puma concolor) management has been hindered by inability to identify population trends. We documented changes in sex and age of harvested cougars during an experimentally induced reduction in population size and subsequent recovery to better understand the relationship between sex-age composition and population trend in exploited populations. The cougar population in the Snowy Range, southeast Wyoming, was reduced by increased harvest (treatment phase) from 58 independent cougars (>1 year old) (90% C***l = 36–81) in the autumn of 1998 to 20 by the spring of 2000 (mean exploitation rate = 43%) and then increased to 46 by spring 2003 following 3 years of reduced harvests (mean exploitation rate = 18%). Pretreatment harvest composition was 63% subadults (1.0–2.5 years old), 23% adult males, and 14% adult females (2 seasons; n = 22). A reduction in subadult harvest, an initial increase followed by a reduction in adult male harvest, and a steady increase in adult female harvest characterized harvest composition trends during the treatment phase. Harvest composition was similar at high and low densities when harvest was light, but proportion of harvested subadult males increased at low density as they replaced adult males removed during the treatment period (high harvest). While sex ratio of harvested cougars alone appears of limited value in identifying population change, when combined with age class the 2 appear to provide an index to population change. Composition of the harvest can be applied to adaptively manage cougar populations where adequate sex and age data are collected from harvested animals. [show more]                

ID: Experiments Show Iron Pollution Limits Fail to Protect Aquatic Species
Experiments Show Iron Pollution Limits Fail to Protect Aquatic Species
Type: Fact Sheet
Subjects: Aquatic animals -- Effect of water pollution on -- Colorado
Metals -- Toxicology -- Colorado
Item 

        Experiments Show Iron Pollution Limits Fail to Protect Aquatic Species    
Type:Fact Sheet
Subject:Aquatic animals -- Effect of water pollution on -- Colorado
Metals -- Toxicology -- Colorado

                    Description:Experiments conducted by Colorado Parks and Wildlife suggest the current water quality standard for iron (Fe) is two to four times higher than it should be to protect Colorado's aquatic life.                

ID: Exploring Alternative Methods for Determining Fishery Characteristics
Exploring Alternative Methods for Determining Fishery Characteristics

Type: 
Subjects: 
Item 

        Exploring Alternative Methods for Determining Fishery Characteristics

    

                    Description:Led By
Jesse ​​Lepak​
Study Area
Four Colorado Reservoirs (Blue Mesa, Granby, Shadow Mountain, Williams Fork)
Project Status
Completed
Research Objectives
To explore less time-consuming and more reliable methods for determining fish age.
Project Description
Understanding lake and reservoir food web structure plays a crucial role in determining how best to manage a sport fishery. In order to inform management decisions, man​agers use a variety of techniques to characterize important aspects of lake and reservoir fisheries.
For example, managers can use otoliths, calcified structures in a fish's inner ear that grow like tree rings, to determine the age of the fish. This information helps managers understand things like fish growth rates, the age structure of a fish population and if certain age classes of fish are missing from the population. This information can help managers identify and potentially address problems in a fish population like disease, poor spawning or recruitment, and overpopulation
Currently, researchers use thin sections of the otoliths to determine the age of the sample fish. However, this method is labor-intensive, requires extensive training and is a subjective classification. Therefore, CPW initiated a research project to determine if otolith mass can be used as a reliable indicator of age. Such a method would require less training, would be faster and would be relatively objective.
During the kokanee salmon spawning runs, researchers collected kokanee salmon from four reservoirs in Colorado. Researchers noted kokanee salmon length and whether the fish was male or female. Otoliths were also extracted from each fish and weighed. A small subset (~30) of otolith sections was used to determine kokanee salmon age and "calibrate" a computer model.  All t​he length and gender data from each fish (hundreds) was then input into the model to estimate ages for all the fish collected. With a relatively low error rate, researchers determined that using otolith mass is a promising addition to traditional age-classification methods.
Results from this study provide managers with a faster and more reliable manner in which to determine fish age in Colorado's lakes and reservoirs. This information will inform future management decisions, streamline methods required to determine fish age and will be applied to the valuable kokanee salmon fishery in Blue Mesa Reservoir. ​
Associated Publications
Lepak, J.M., Cathcart, C.N., and Hooten, M.B. 2012. Otolith weight as a predictor of age in kokanee salmon (Oncorhynchus nerka) from four Colorado reservoirs. Canadian Journal of Fisheries and Aquatic Sciences. 69(10):1569-1575. 
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