Adam Hansen

Contact Information

317 W Prospect Rd, Fort Collins, CO 80526
Email: adam.hansen@state.co.us
Phone: 970-472-4432

• Research Gate profile
• CV

Education

• Ph.D., Aquatic and Fishery Science — University of Washington, 2014
• B.S., Fishery Biology — Colorado State University, 2008

Current or Recent Positions

• Aquatic Research Scientist – Colorado Parks and Wildlife, 2015-Current
• Research Scientist Engineer III – Washington Cooperative Fish and Wildlife Research Unit, School of Aquatic and Fishery Sciences, University of Washington, 2013-2015
• Graduate Fellow and Research Assistant – Washington Cooperative Fish and Wildlife Research Unit, School of Aquatic and Fishery Sciences, University of Washington, 2009-2013
• Research Associate I – Department of Fish, Wildlife, and Conservation Biology, Colorado State University, 2008-2009

Current or Recent Research Projects

• Evaluating sterile predators as a management tool.
• ​Post-stocking performance of triploid walleye.
• Evaluating standard sampling protocols for assessing sport fish populations.
• Evaluating the biological effectiveness of angler harvest incentive programs.
• Population assessment of pelagic fishes using hydroacoustics.
• Reservoir food webs and predator-prey interactions.
• Understanding and managing gill lice infections in reservoir sport fish.
• Understanding and managing mercury bioaccumulation in sport fish.

Areas of Interest/Expertise

I’m broadly interested in the ecology of large lakes and reservoirs. I research how interactions among climate, human use, reservoir operations, environmental conditions, fish behavior and physiology, and food web structure work to either limit or promote the growth and survival of native and sport fish. I use field sampling, modeling, and the occasional experiment to diagnose the primary factors (i.e., harvest, habitat, food supply, competition, predation, and disease) limiting the production of important populations of fish and to identify/evaluate alternative approaches for improving or maintaining lake and reservoir fisheries.  

Publications

Chao Guo, Wei Li, Shiqi Li, Chuansong Liao, Jie Ke, Xingwei Chi, A. G. Hansen, Chuanbo Guo, and Jiashou Liu. In press. Density-dependent effects of zooplanktivorous thin sharpbelly (Toxabramis swinhonis) on plankton assemblages and water quality: implications for lake rehabilitation. Water Biology and Security.

Lepak, J. M., A. G. Hansen, B. M. Johnson, K. Battige, E. T. Cristan, C. J. Farrell, W. M. Pate, K. B. Rogers, A. J. Treble, and T. W. Walsworth. In press. Cyclical multi-trophic-level responses to a volatile, introduced forage fish: learning from four decades of food web observation to inform management. Fisheries.

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 (2nd edition). Edited by S. A. Bonar, W. A. Hubert, and D. W. Willis. American Fisheries Society, Bethesda, Maryland.

Farrell, C.J., A.G. Hansen, M.M. Brandt, C.A. Myrick, and B.M. Johnson. 2024. An evaluation of the relative size, body condition, and survival of triploid Walleye in the wild. North American Journal of Fisheries Management 44(1):172-188.

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(4): e12699.

Lepak, J.M., W.M. Pate, P. Cadmus, A.G. Hansen, K.D. Gallaher, and D.B. Silver.  2024. Response of an invasive aquatic crustacean to the fish toxicant rotenone. Lake and Reservoir Management 40(3):330-337.

Li, S., C. Guo, C. Liao, J. Ke, A.G. Hansen, X. Shi, T. Zhang, E. Jeppesen, W. Li, and J. Liu. 2024. Improvement of water quality through coordinated multi-trophic level biomanipulations: Practice in a subtropical emergency water supply lake. Science of The Total Environment 955:176888.

Chao Guo, Shiqi Li, Jie Ke, Chuansong Liao, A. G. Hansen, E. Jeppesen, Tanglin Zhang, Wei Li, and Jiashou Liu. 2023. The feeding habits of small-bodied fishes mediate the strength of top-down effects on plankton and water quality in shallow subtropical lakes. Water Research 233:119705.

Hansen, A. G., C. J. Farrell, and B. M. Johnson. 2023. Simulated effects of imperfect sterile sport fish stocking on persistence of fertile fish in new exploited populations. North American Journal of Fisheries Management 43:908-934 (Feature Article).

Hansen, A.G., A.K. McCoy, G.P. Thiede, and D.A. Beauchamp. 2023. Pelagic food web interactions in a large invaded ecosystem: implications for reintroducing a native top predator. Ecology of Freshwater Fish 32:552-570.

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.

Lepak, J. M., B. M. Johnson, M. B. Hooten, B. A. Wolff, and A. G. Hansen. 2023. Predicting sport fish mercury contamination in heavily managed reservoirs: implications for human and ecological health. Environmental Science and Technology 18(8):e0285890.

Chao Guo, Shiqi Li, Wei Li, Chuansong Liao, Tanglin Zhang, Jiashou Liu, Lin Li, Jiaxin Sun, Xingwei Cai, and A. G. Hansen. 2022. Spatial variation in the composition and diversity of fishes inhabiting an artificial water supply lake, Eastern China. Frontiers in Ecology and Evolution 10:921082.

Cristan, E. T., A. G. Hansen, and J. M. Lepak. 2022. Effects of ethanol preservation on larval and juvenile walleye and gizzard shad body size. North American Journal of Fisheries Management 42:874-881.

Farrell, C. J., B. M. Johnson, A. G. Hansen, C. M. Myrick, E. C. Anderson, T. A. Delomas, A. D. Schreier, and J. P. Van Eenennaam. 2022. Cytological and molecular approaches for ploidy determination: results from a wild walleye population. North American Journal of Fisheries Management 42:849-856.

Farrell, C. J., B. M. Johnson, A. G. Hansen, and C. A. Myrick. 2022. Induced triploidy reduces mercury bioaccumulation in a piscivorous fish. Canadian Journal of Fisheries and Aquatic Sciences 79:200-212 (2022 Editor’s Choice Award).

Guo, C., L. Wei, L. Shiqi, M. Zhan, T. Zhang, J. Liu, A. G. Hansen, L. Lin, X. Cai, and B. J. Hicks. 2022. Manipulation of fish community structure effectively restores submerged aquatic vegetation in a shallow subtropical lake. Environmental Pollution 292:118459.

Hansen, A. G., E. T. Cristan, M. M. Moll, 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.

Hansen, A. G., J. A. Gardner, K. A. Connelly, M. Polacek, and D. A. Beauchamp. 2022. Resource use among top-level piscivores in a temperate reservoir: implications for a threatened coldwater specialist. Ecology of Freshwater Fish 31:469-491.

Lepak, J. M., A. G. Hansen, M. B. Hooten, D. Brauch, and E. M. Vigil. 2022. Rapid proliferation of the parasitic copepod, Salmincola californiensis (Dana), on kokanee salmon, Oncorhynchus nerka (Walbaum), in a large Colorado reservoir. Journal of Fish Diseases 45:89-98 (Received cover image for issue).

Rohan, S. K., D. A. Beauchamp, T. E. Essington, and A. G. Hansen. 2021. Merging empirical and mechanistic approaches to modeling aquatic visual foraging using a generalizable visual reaction distance model. Ecological Modelling 457:109688.

Farrell, C. J., B. M. Johnson, C. A. Myrick, and A. G. Hansen. 2019. Triploid walleye: a new frontier for managing coolwater predators in the West. Colorado State University, Department of Fish, Wildlife, and Conservation Biology, and Colorado Parks and Wildlife, Aquatic Research Section. Fort Collins, CO. 86pp.

Hansen, A. G., J. S. Thompson, L. N. Hargis, D. Brauch, and B. M. Johnson. 2019. Predatory threat of introduced yellow perch in a salmonid-dominated reservoir food web. North American Journal of Fisheries Management 39:172-190.

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

Litz, M. N. C., J. A. Miller, R. D. Brodeur, E. A. Daly, L. A. Weitkamp, A. G. Hansen, and A. M. Claiborne. 2019. Energy dynamics of subyearling Chinook salmon reveal the importance of piscivory to short term growth during early marine residence. Fisheries Oceanography 28:273-290. 

Hansen, A.G., J.A. Gardner, K.A. Connelly, M. Polacek, and D.A. Beauchamp. 2018. Trophic compression of lake food webs under hydrologic disturbance. Ecosphere 9(6):e02034.

Spanjer, A.R., P.W. Moran, K.A. Larsen, L.A. Wetzel, A.G. Hansen, and D.A. Beauchamp. 2018. Juvenile coho salmon growth and health in streams across an urbanization gradient. Science of the Total Environment 625:1003-1012. 

Johnson, B.M., W.M. Pate, and A.G. Hansen. 2017. Energy density and dry matter content in fish: new observations and an evaluation of some empirical models. Transactions of the American Fisheries Society 146:1262-1278. 

Borin, J.M., M.L. Moser, A.G. Hansen, C. Donoghue, D.A. Beauchamp, C. Pruitt, S.C. Corbett, J.L. Ruesink, and B. Dumbauld. 2017. Energetic requirements of the North American green sturgeon (Acipenser medirostris) feeding on burrowing shrimp (Neotrypaea californiensis) in estuaries: importance of temperature, reproductive investment, and residence time. Environmental Biology of Fishes 100:1561-1573.

Hansen, A.G., J.R. Gardner, D.A. Beauchamp, R. Paradis, and T.P. Quinn. 2016. Recovery of sockeye salmon in the Elwha River, Washington, after dam removal: dependence of smolt production on the resumption of anadromy by landlocked kokanee. Transactions of the American Fisheries Society 145:1303-1317.

Sorel, M.H., A.G. Hansen, K.A. Connelly, and D.A. Beauchamp. 2016. Trophic feasibility of reintroducing anadromous salmonids in three reservoirs on the North Fork Lewis River, Washington: prey supply and consumption demand of resident fishes. Transactions of the American Fisheries Society 145:1331-1347.​

Sorel, M.H., A.G. Hansen, K.A. Connelly, A.C. Wilson, E.D. Lowery, and D.A. Beauchamp. 2016. Predation by northern pikeminnow and tiger muskellunge on juvenile salmonids in a high-head reservoir: implications for anadromous fish reintroductions. Transactions of the American Fisheries Society 145:521-536.

Hovel, R.A., D.A. Beauchamp, A.G. Hansen, and M.H. Sorel. 2015. Development of a bioenergetics model for the threespine stickleback Gasterosteus aculeatus. Transactions of the American Fisheries Society 144:1311-1321.

Hansen, A.G., and D.A. Beauchamp. 2015. Latitudinal and photic effects on diel foraging and predation risk in freshwater pelagic ecosystems. Journal of Animal Ecology 84:532-544.

Hansen, A.G., and D.A. Beauchamp. 2014. Effects of prey abundance, distribution, visual contrast, and morphology on selection by a pelagic piscivore. Freshwater Biology 59:2328-2341.

Garcia, R.L., A.G. Hansen, M. Chan, and G.E. Sanders. 2014. Gyrodactylid Ectoparasites in a population of rainbow trout (Oncorhynchus mykiss). The Journal for the American Association for Laboratory Animal Science 53:92-97.

Hansen, A.G., D.A. Beauchamp, and E.R. Schoen. 2013. Visual prey detection responses of piscivorous trout and salmon: effects of light, turbidity, and prey size. Transactions of the American Fisheries Society 142:854-867.

Hansen, A.G., D.A. Beauchamp, and C.M. Baldwin. 2013. Environmental constraints on piscivory: insights from linking ultrasonic telemetry to a visual foraging model for cutthroat trout. Transactions of the American Fisheries Society 142:300-316.

Lepak, J.M., K.D. Kinzli, E.R. Fetherman, W.M. Pate, A.G. Hansen, E.I. Gardunio, C.N. Cathcart, W.L. Stacey, Z.E. Underwood, M.M. Brandt, C.M. Myrick, and B.M. Johnson. 2012. Manipulation of growth to reduce mercury concentrations in sport fish on a whole-system scale. Canadian Journal of Fisheries and Aquatic Sciences 69:122-135.​