Triploid Walleye: A New Frontier for Managing Coolwater Predators in the West (2018-present)
Graduate Students: Collin Farrell (MS)
Collaborators: Mandi Brandt, Ben Felt, Adam Hansen, Jim White (CPW)
Sponsor: Colorado Parks and Wildlife

Walleye (Sander vitreus) are a widely distributed and important recreational fish species throughout the United States and Canada, but they are not native to Colorado. Walleye can be invasive and negatively impact native species in their introduced range, and stocking is prohibited in many parts of the western U.S. However, illegal introductions and natural dispersal are common and managers need a means to limit the impact of introduced Walleye. Stocking triploids has been proposed as an alternative stocking method for walleye throughout the West. Triploid fish have three sets of chromosomes as compared to normal, or diploid, fish which have two sets of chromosomes. Triploid fish are much less fertile than their diploid counterparts, which could prevent the establishment of new Walleye populations in sensitive areas. However, almost nothing is known about the performance of triploid Walleye in the wild. This study will examine triploid Walleye life history, diet, growth, and survival and how these factors compare relative to diploid walleye.

Lake Sediment Coring to Detect Environmental Perturbations and Species Introductions (2016-present)
Staff: Bill Pate, Doug Silver, Ben Galloway
Collaborators: Denver Water
Sponsors: private gift to the Colorado State University Foundation

The environmental history of lakes and reservoirs is recorded in the sediment layer at the bottom. Detailed examination of sediment core samples allows us to infer past water quality and food web configuration. We are also developing and testing methods to use environmental DNA (eDNA) to determine when nonnative species (fish, Mysis shrimp) were introduced. This technology has tremendous application for studying the history of lacustrine systems throughout the Western U.S. and beyond.

Sensitivity of Alpine Lakes to Climate Change (2014-present)
Graduate students: Kyle Christianson (PhD)
Collaborators: James Roberts (USGS), Kyle Battige (CPW)
Sponsors: NSF/CSU I-WATER, and a private gift to the CSU Foundation

Lakes are sentinels for climate change because they are sensitive to climate and they respond rapidly to change. Coldwater lakes are particularly sensitive to a warming climate that may reduce duration of ice cover and increase the duration and intensity of thermal stratification. These changes can have implications for ecosystem productivity, food web interactions and the sport fisheries that can be sustained. Despite the fact that >90% of natural lakes in Colorado are above 9,000 ft elevation, there have been few studies predicting how Colorado’s high elevation lakes will respond to climate change. This study is gathering meteorological and limnological data that are being used to calibrate the General Lake Model. The GLM will then be used to predict lake thermal regimes resulting from future climate scenarios, and bioenergetics models will evaluate ecological implications.

Status of Opossum Shrimp (Mysis diluviana) in the Intermountain West (2010-present)
Staff: Bill Pate, Doug Silver, Ben Galloway
Collaborators: Adam Hansen (CPW)
Sponsor: private gift to the CSU Foundation

The freshwater Opossum shrimp (Mysis diluviana) was introduced into lakes and reservoirs across western North America during the 1950s to 1970s to supplement food resources for trout and salmon. However, the plan mostly backfired and the shrimp became competitors with fish instead of prey. Opossum shrimp were introduced into almost 60 waters in Colorado, and they may have invaded another 50 downstream waters. However, other than the outstanding work by now retired CPW biologist Pat Martinez on large reservoirs, there has been very little evaluation of the outcomes of these introductions/invasions and the current status of this potentially invasive species in Colorado, Wyoming and Utah is largely unknown.

Quantifying Piscivory in Buffalo Bill Reservoir: Are the wild Oncorhynchus fisheries sustainable? (2012-2015)
Graduate students: Clark Johnson (MS)
Collaborators: Jason Burkhardt, Travis Neebling, Mark Smith (WGF)
Sponsor: Wyoming Game and Fish Department

Buffalo Bill Reservoir (BBR) in northwest Wyoming supports a very popular, entirely wild, self-sustaining trout fishery, with all stocking discontinued in 1995. Yellowstone cutthroat trout, rainbow trout, and their hybrids have typically dominated the fishery. A recent upsurge in lake trout combined with the illegal introduction of walleye has biologists concerned about present and future predation pressure on the wild trout populations.

Effects of Water Clarity and Other Factors on Aquatic Life of Grand Lake, Colorado (2015)
Staff: Bill Pate
Collaborators: Esther Vincent (NCWCD), Jon Ewert (CPW).
Sponsor: Northern Water

The Colorado-Big Thompson Project collects and transfers water from the west side of the Continental Divide to the Front Range through a tunnel the runs beneath Rocky Mountain National Park. Water is pumped into Grand Lake, Colorado’s largest natural lake, where it enters the tunnel. This pumping reduces water clarity of Grand Lake. This project evaluated the effects of reduced water clarity and other factors on aquatic life in Grand Lake, Colorado.

Dillon Reservoir Food Web and Fishery (2010-2013)
Graduate students: Devin Olsen.
Collaborators: Jesse Lepak, Jon Ewert (CPW).
Sponsor: private gift to the CSU Foundation

Many coldwater reservoirs in Colorado and across western North America suffer from several constraints that inhibit productive sport fisheries. Oligotrophication (reduced nutrients), water level fluctuation, and introduced Mysis shrimp work together to limit the energy available for sport fish growth. Arctic char were hypothesized as a potential management solution because they evolved in cold, oligotrophic lakes and they prey heavily on Mysis shrimp. Arctic char were stocked into Dillon by CPW beginning in 1990, and annual stocking has continued since 2008, but almost nothing was known of the success of this program. A private sponsor funded this study in 2010 to investigate the Arctic char of Dillon Reservoir.

Mercury Bioaccumulation and Mitigation Strategies (2011-2015)
Staff: Brian Wolff
Collaborators: Jesse Lepak (CPW)
Sponsors: US-EPA and Colorado Department of Public Health and Environment

The overall goal of this project was to evaluate the efficacy of a variety of fishery management strategies for minimizing mercury bioaccumulation in sport fishes.  We gathered field data to 1) identify the ‘risk factors’ that drive methylmercury concentrations in reservoirs; 2) evaluate the prospects for fishery management strategies (e.g., prey base manipulation, stocking, and harvest regulation scenarios) to mitigate mercury contamination across a wide range of reservoirs throughout the state.

Otolith Chemistry for Tracing Origins of June Sucker (2010-2012)
Staff: Brian Wolff
Collaborators: Chad Landress, Krissy Wilson, Utah Division of Wildlife Resources
Sponsor: June Sucker Recovery Program, UDWR

Management Strategies to Sustain Kokanee and Lake Trout at Blue Mesa Reservoir (2009-2012)
Graduate students: Bill Pate (MS)
Collaborators: Dan Brauch, CPW
Sponsors: CDOW, NPS

Chemically fingerprinting Nonnative Fishes in Reservoirs (2006-2014)
Graduate students: Brian Wolff
Collaborators: Pat Martinez (CPW), Jurek Blusztajn (Woods Hole Oceanographic Institution)
Sponsors: Bureau of Reclamation/Upper Colorado River Endangered Fish Recovery Program

Management of Mercury Bioaccumulation in Colorado Reservoirs  (2009-2010)
Post-doc: Jesse Lepak
Collaborators: Nicole Vieira, Ken Kehmeier (CPW)
Sponsors: CPW

Illegal Stocking of Aquatic Organisms (2009)
Sponsors: Colorado-Wyoming Chapter, American Fisheries Society
Pro bono

Fishery Assessment at Rifle Gap Reservoir (2008)
Collaborators: Lori Martin (CPW)
Pro bono

Effects of an Anticipated Illegal Introduction of Walleye into Blue Mesa Reservoir (2006)
Collaborators: Dan Brauch (CPW)
Pro bono

Forensic Applications of Otolith Microchemistry for Tracing Sources of Illegally Stocked Fishes (2004-2006)
Graduate students: Dan Gibson-Reinemer (MS)
Collaborators: Pat Martinez (CPW)
Sponsors: Whirling Disease Initiative)

Provenance of Nonnative Fishes in the Upper Colorado River Basin (2003-2005)
Post-doc: Greg Whitledge
Collaborators: Pat and Anita Martinez (CPW)
Sponsors: Bureau of Reclamation/Upper Colorado River Endangered Fish Recovery Program

Illegal Stocking of Sport Fish: Impacts and Interdiction
Collaborators: Pat Martinez (CPW)

Food Web Dynamics in Colorado’s Coldwater Reservoirs
Collaborators: Pat Martinez (CPW)
Sponsors: CPW

Ecosystem Monitoring during Horsetooth Reservoir Refilling
Collaborators: Davine Leiberman, Beth Boaz (Bureau of Reclamation)
Sponsors: Bureau of Reclamation

Effects of Nitrogen Deposition on Alpine Lakes (1998-2002)
Graduate students: Brenda Moraska (La Francois), Koren Nydick
Collaborators: Jill Baron (USGS);
Sponsors: USGS, National Park Service

Ecological Effects of Reservoir Operations on Blue Mesa Reservoir (1993-2006)
Graduate students: Mike Wise, Jill Hardiman, Marci Koski, Harry Crockett
Collaborators: Ron Sutton, Steve McCall (Bureau of Reclamation)
Sponsors: Bureau of Reclamation

Effects of Sediment Contaminants on Fish at the Rocky Mountain Arsenal (1994-1997)
Graduate students: Nicole MacRury (Vieira)
Collaborators: Will Clements (CSU)
Sponsors: USFWS

Ecology and Conservation of Rio Grande Sucker (1994-1995)
Graduate student: Sue Swift
Collaborators: John Alves (CPW);
Sponsors: CPW, USFS

Trophic Interactions in Colorado Reservoirs (1993-1999)
Graduate students: Steve Johnson (MS)
Collaborators: Patrick Martinez, John Goettl (CPW)
Sponsors: CPW