Stock Discrimination and Population Connectivity


Many animal populations are composed of subpopulations that spend at least some time spatially separated. These subpopulations often contribute new recruits to the broader population in different ways.

For this research component, the goals of my work are to

  1. Identify the degree to which subpopulations are connected and overlap in space and time,
  2. Quantify the relative contributions of recruits from these subpopulations, and
  3. Reveal the causes and consequences of these patterns in subpopulation connectivity and production.

To facilitate these efforts, we use the “natural tags” of genetic differences and microchemical differences in the otoliths (ear “stones”) of fish spawned in different geographic areas. These tags help differentiate subpopulations and contribute to our ability to understand the demographics and dynamics of the broader population, which in turn helps with the identification of strategies to sustainably manage fisheries.  Sustainable management includes informing catch limits for commercially fished populations as well as the identification of key production sites of invasive species like sea lamprey for targeted removal.

Selected Projects

Habitat quality as a driver of Lake Erie walleye population dynamics: Past, present, and future

Walleye telemetry – Use of Lake Erie’s Ohio reef complex by walleye during the spring spawning season

Selected Refereed Publications

  1. Chen, K.Y., E.A. Marschall, M.G. Sovic, A.C. Fries, H.L. Gibbs, and A. Ludsin. 2018. assignPOP: An R package for population assignment using genetic, non‐genetic, or integrated data in a machine‐ learning framework. Methods in Ecology and Evolution 9:439-446.
  2. Chen, K.-Y., S.A. Ludsin, M.M. Corey, P.D. Collingsworth, M.K. Nims, J.W. Olesik, K. Dabrowski, J.J. van Tassell, and E.A. Marschall. 2017. Experimental and field evaluation of otolith strontium as a marker to discriminate between river-spawning populations of walleye in Lake Erie. Canadian Journal of Fisheries and Aquatic Sciences 74:693-701.
  3. DuFour, M.R., May, C.J., Roseman, E.F., Mayer, C.M., S.A. Ludsin, C.S. Vandergoot, J.J. Pritt, M.E. Fraker, J.J. Davis, J.T. Tyson, J.G. Miner, and E.A. Marschall. 2015. Portfolio theory as a management tool to guide conservation and restoration of multi-stock fish populations. EcoSphere 6: article 296 (21 pp.)
  4. Fraker, M.E., E.J. Anderson, C.J. May, K.Y. Chen, J.J. Davis, K.M. DeVanna, M.R. DuFour, E.A. Marschall, C.M. Mayer, J.G. Miner, K.L. Pangle, J.J. Pritt, E.F. Roseman, J.T. Tyson, Y. Zhao, and S.A. Ludsin. 2015. Stock-specific advection of larval walleye (Sander vitreus) in western Lake Erie: implications for larval growth, mixing, and stock discrimination. Journal of Great Lakes Research 41:830–845.
  5. Fraker, M.E., E.J. Anderson, R. Brodnik, L. Carreon-Martinez, K.M. DeVanna, B.J. Fryer, D.D. Heath, J.M. Reichert, and S.A. Ludsin. 2015. Particle backtracking improves breeding subpopulation discrimination and natal-source identification in mixed populations. Plos One 10(3):e0120752.
  6. Lochet, A., B.J. Fryer, S.A. Ludsin, and J.E. Marsden. 2014. Identifying natal origins of spawning adult sea lamprey (Petromyzon marinus): re-evaluation of the statolith microchemistry approach. Journal of Great Lakes Research 40:763-770.
  7. Howe, E.A., A. Lochet, C.P. Hand, S.A. Ludsin, J.E. Marsden, and B.J. Fryer. 2013. Discriminating natal origin of spawning adult sea lamprey (Petromyzon marinus) in Lake Champlain using statolith elemental signatures. Journal of Great Lakes Research 39:239-246.
  8. Lochet, A. J.E. Marsden, B.J. Fryer, and S.A. Ludsin. 2013. Instability of statolith elemental signatures revealed in newly metamorphosed sea lamprey (Petromyzon marinus). Canadian Journal of Fisheries and Aquatic Sciences.
  9. Pangle, K.L., S.A. Ludsin, and B.J. Fryer. 2010. Otolith microchemistry as a stock identification tool for freshwater fishes: testing its limits in Lake Erie. Canadian Journal of Fisheries and Aquatic Sciences 67:1475–1489.
  10. Hand, C.P, S.A. Ludsin, B.J. Fryer, and J.E. Marsden. 2008. Statolith microchemistry as a technique for discriminating among Great Lakes sea lamprey (Petromyzon marinus) spawning tributaries. Canadian Journal of Fisheries and Aquatic Sciences 65:1153-1164.
  11. Melancon, S., B.J. Fryer, J.E. Gagnon, and S.A. Ludsin. 2008. Mineralogical approaches to the study of biomineralization in fish otoliths. Mineralogical Magazine 72(2):627-637.
  12. Ludsin, S.A., B.J. Fryer, and J.E. Gagnon. 2006. Comparison of solution-based versus laser-ablation ICPMS for analysis of larval fish otoliths. Transactions of the American Fisheries Society 135:218–231.
  13. Melancon, S. B.J. Fryer, J.E. Gagnon, Z. Yang, and S.A. Ludsin. 2005. Effects of crystal structure on the uptake of metals by lake trout (Salvelinus namaycush) otoliths. Canadian Journal of Fisheries and Aquatic Sciences 62:2609-2619.
  14. Hedges, K.J., S.A. Ludsin, and B.J. Fryer. 2004. Effects of ethanol preservation on otolith micro-chemistry. Journal of Fish Biology 64:923-947.
  15. Sale, P.F., and S.A. Ludsin. 2003. The extent and spatial scale of connectivity among reef fish populations: implications for marine protected areas designated for fisheries enhancement. Gulf and Caribbean Research 14:119-128.

Relevant Funding

  • Great Lakes Fishery Commission
    • Fisheries Research Program
      • “Do discrete spawning stocks contribute differentially to Lake Erie’s walleye fisheries?” Co-PI, 2016-2020.
      • “Habitat quality as a driver of Lake Erie walleye population dynamics: past, present, and future.” PI, 2016-2020; Michael Fraker, Dave Glover, Conor Keitzer, Noel Aloysius (all former post-docs), Dave Dippold (PhD student)
      • “A coupled physical-biological model to forecast larval yellow perch distributions, growth rates, and potential recruitment in Lake Erie.” Co-PI, 2011-2013; Kevin Pangle (former post-doc)
      • “River discharge as a predictor of Lake Erie yellow perch recruitment.” PI, 2006-2011; Julie Reichert (former MS student), Kevin Pangle (former post-doc)
      • “Exploration of the existence of natural reproduction in Lake Erie lake trout using otolith microchemistry.” Co-PI, 2003-2004.
    • Sea Lamprey Research Program
      • “Determination of micro-elemental stability of sea lamprey statoliths.” Co-PI, 2009-2012; Carrol Hand (former MS student)
      • “Micro-elemental analysis of statoliths as a tool for tracking tributary origins of sea lamprey.” PI, 2004-2006; Carrol Hand (former MS student)
  • Ohio Department of Natural Resources – Division of Wildlife, Federal Aid in Sport Fish Restoration Project Funds
    • “FADR78: Walleye use of the Lake Erie reef complex during the spring spawning season.” PI, 2016-2020; Andrew Bade (PhD student)
    • “FADR68: Lake Erie walleye stock discrimination methods and applications.” PI, 2011-2013; Alex Chen (former PhD student)
    • “FADR69: Role of biophysical coupling in walleye recruitment.” PI, 2011-2013; Mike Fraker (former post-doc), Kristen Devanna Fussell (former post-doc), Kevin Pangle (former post-doc)
  • Ohio Sea Grant College Program: “Stock structure and contribution of west and east basin walleye to recreational and commercial fisheries in Lake Erie.” PI, 2018-2020.
  • Lake Champlain Sea Grant Program: “Development of a population viability model to optimize sea lamprey control strategies in Lake Champlain.” Co-PI, 2004-2006; Carrol Hand (former MS student)