Department of Biology

B.S., 1993, University of Wisconsin Stevens Point
M.S., 1995, University of Wisconsin Madison
Ph.D., 1999, University of Wisconsin Madison

Office: 11 SSB
Phone: 726-7626

Curriculum vitae

My Google Scholar Page


Aquatic Ecology, Fisheries, Hydroacoustics

My research program examines several aspects of fisheries ecology. Current projects are focused on studying the interactions between exotic and native fishes, the effects of changing climate on habitat quality for cold water fishes, nutrient regeneration-translocation by vertically migrating fauna in the recovering food web of Lake Superior and individual based modeling. While this group of topics is diverse, each is important for they are focused on examining the influence of human induced environmental change on aquatic communities.

Fish populations are a vital source of revenue for economic interests in sport and commercial fisheries, as well as a vital link in ecosystem processes that influence water quality. Understanding linkages between aquatic species and ecosystems is vital to predicting the effects of changing the natural environment.


Recent Publications

  • Hrabik, T.R., B.M. Roth and T.D. Ahrenstorff*. 2014. Predation risk and prey fish vertical migration in Lake Superior: insights from an individual based model of siscowet (Salvelinus namaycush)? In Press. J. Great. L. Res.
  • Sierszen, M.J. T.R. Hrabik, J.D. Stockwell, D.L Yule, L. Evrard, A.E. Gamble. 2014. Depth gradients in food web processes linking large lake habitats: Lake Superior as an example ecosystem. In Press. Freshwater Biology.
  • Gaeta, J., T. R. Hrabik,,G.G. Sass, B.M. Roth, G. Hansen, S. Gilbert and J. Vander Zanden. 2014. Dynamics of rainbow smelt under altered predation and fishing mortality. In Press. Hydrobiologia.
  • Yurista, P., M. Balge, J. VanAlstine, T.R. Hrabik, A. Gamble, D. Yule, J. Stockwell, J. Kelly. 2014. A new look at the Lake Superior biomass size-spectrum. In Press. Can. J. Fish. Aquat. Sci.
  • Stockwell, J.D., D.L. Yule, T.R. Hrabik, M.E. Sierszen and E.J. Issac. 2014. Habitat coupling in a large lake system: delivery of an energy subsidy by an offshore planktivore to the nearshore zone of Lake Superior. Freshwater Biology. DOI:10.1111/fwb.12340.
  • Janssen, J., J.E. Marsden, T. R. Hrabik and J.D. Stockwell. 2014. Are the Laurentian Great Lakes Great Enough for Hjort? ICES J. Mar. Sci. DOI: 10.1093/icesjms/fst220.
  • Yule, D.L., J. Adams, D. Warner, T.R. Hrabik, B.Wiedel. 2013. Evaluating approaches for estimating biomass of pelagic fish species using simulated fish communities. Can. J. Fish. Aquat. Sci. 70:1845-1857.
  • Ahrenstorff, T.D.*, Hrabik, T.R., Jacobson, P.C., and Pereira, D.L.  2013. Food resource effects on diel movements and body size of cisco (Coregonus artedi) in north-temperate lakes. Oecologia. 173:1309-1320. DOI 10.1007/s00442-013-2719-3.
  • Yule, D.L., J. Adams, T.R. Hrabik, J. Woiak, M. Vinson, T. Ahrenstorff. 2013. Use of Classification Trees to Apportion Acoustic Targets to Species: Application to the 2011 Lake-wide Acoustic and Midwater Trawl Survey of Lake Superior. Fisheries Research 140:123-132.
  • Holbrook B.V,* T.R. Hrabik, D.B. Branstrator and A. Mensinger. 2013. Foraging Mechanisms of Age-0 Lake Trout (Salvelinus namaycush). Journal of Great Lakes Research. 39:128–137.

* Graduate Student papers



  • BIOL 3835 Freshwater Ecology
  • BIOL 4761 Ichthyology
  • BIOL 5805 Fisheries Ecology
  • BIOL 2802 Ecology Lab
  • IBS 8201 Ecological Processes


Current Graduate Student Projects

  • Emily Heald (M.S. Integrated Biosciences) (Primary Advisor). Determinants of spatial correlation in pelagic fish and zooplankton distributions).
  • Kirk Olson (M.S., Integerated Biosciences) (Primary Advisor). Thesis – Niche partitioning and diet characteristics of Arctic grayling, Hovsgol grayling and sharp-nosed lenok in Mongolia.
  • Trevor Keylor (M.S., Integrated Biosciences) (co-advisor w/Mensinger). Thesis – Foraging mechanisms in deepwater fishes in Lake Superior.
  • Matt Pawlawski (M.S., Integrated Biosciences) (co-advisor w/Branstrator). Thesis – TBA
  • Ian Harding (M.S., Integrated Biosciences) (co-advisor w/Branstrator). Thesis – TBA
  • Halvor Adams (M.S., Integrated Biosciences). Thesis -- TBA


Recently Completed Graduate Student Projects

  • Samantha Oliver (M.S., Integrated Biosciences )(co-advisor w/Branstrator). Thesis - Nutrietnt regeneration by zooplankton in Lake Superior.
  • Tyler Kasper (M.S., Integrated Biosciences) (Primary Advisor). Thesis - Factors influencing migratory rainbow trout recruitment in Lake Superior.
  • Edmund Issac. MSc. Evaluation of Mysis relicta as a keystone species in the food web of Lake Superior.
  • Allison Gamble. Ph.D. The influence of habitat characteristics on trophic exchange in Lake Superior.
  • Beth Holbrook. Ph.D. The role of mesoscale eddies in the ecology of offshore waters of Lake Superior.


Recent UROP Student Projects

  • Marc Sizer. Mortality of deepwater Lake Superior fishes.



Fishing, skiing, scuba diving, canoeing, and camping.

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