Benjamin D WaltherAssistant Professor, Research Affiliate - Sr Research Fellow
Department of Marine Science, Environmental Science Institute, Jackson School of GeosciencesFish Migration Ecology, Nursery Habitat Ecology, Population Connectivitybwalther@utexas.edu
The University of Texas at Austin
Mar Sci Inst-Port Aran
750 Channel View Dr
Port Aransas, TX 78373
Ph.D., Woods Hole Oceanographic Institution/Massachusetts Institute of Technology (2007)
B.S., Biology, The University of Texas at Austin (2000)
B.A., Plan II, The University of Texas at Austin (2000)
Fish Migration Ecology, Nursery Habitat Ecology, Population Connectivity
Coastal fish migration dynamics, otolith chemistry & natural geochemical tags to quantify population connectivity, nursery habitat requirements, diadromy, and environmental proxies in biogenic carbonates including corals and bivalves.
My research focuses on using the “natural tag” properties of carbonate hard parts in marine and diadromous fishes to examine dynamics of migration, dispersal, and life history dynamics of species with mobile phases. This field has grown exponentially in the past couple of decades, yet many questions remain about highly migratory or dispersive species, particularly in the marine environment. Otolith chemistry has the potential to reveal key information about identity and movement patterns that is essential for the effective management of exploited species and ecosystems. I am particularly keen to combine otolith chemistry methods with alternative approaches to assess movement and connectivity, including genetics, tissue stable isotopes, and satellite telemetry. I strongly believe the combination of these diverse methods can potentially triangulate questions that would be difficult to answer using only one approach.
A second major area of interest is the degree to which environmental events such as can be detected in chemical signatures of both otoliths and other biogenic carbonates (e.g. corals, bivalve shells). For instance, Ba/Ca ratios are most abundant in nutrient-rich waters and they can serve as powerful proxies for temporal fluctuations in upwelling or sediment plumes in reef or estuarine habitats. Analyses of these proxies in carbonate skeletal hard parts allow us to reconstruct time series of environmental variability for specific habitats. This information is essential in order to better understand the response of fish population dynamics to anthropogenic perturbations.
Current lab research involves species and habitats in the Gulf of Mexico, the North Atlantic, and the Great Barrier Reef. Specific topics of interest include 1) ontogenetic shifts in coastal distributions and population mixing of migratory fishes (e.g. American shad in the North Atlantic); 2) variation in habitat use patterns among discrete populations of diadromous species (e.g. southern flounder in Texas, barramundi in northern Australia); 3) influence of energetic status on population connectivity patterns (e.g. black bream in southern Australia); 4) flood and upwelling events recorded in Porites coral skeletons and damselfish otoliths (Great Barrier Reef).
Walther, B.D., T. Dempster, M. Letnic and M.C. McCulloch. 2011. Movements of diadromous fish in large unregulated tropical rivers inferred from geochemical tracers. PLoS ONE 6:e18351.
Walther, B.D., Kingsford, M.J., O’Callaghan, M. and M.C. McCulloch. 2010. Interactive effects of ontogeny, food ration and temperature on elemental incorporation in otoliths of a coral reef fish. Environmental Biology of Fishes 89:441-451.
Walther, B.D. and S. R. Thorrold. 2010. Limited diversity in natal origins of immature anadromous fish during ocean residency. Canadian Journal of Fisheries and Aquatic Sciences 67:1699-1707.
Walther, B.D., Gillanders, B.M., and T.S. Elsdon. 2010. Interactive effects of food quality, temperature and rearing time on condition of juvenile black bream Acanthopagrus butcheri. Journal of Fish Biology 76:2455-2468.
Walther, B.D. and S. R. Thorrold. 2009. Inter-annual variability in isotope and elemental ratios recorded in otoliths of an anadromous fish. Journal of Geochemical Exploration 102:181-186.
Clarke, L.M., Walther, B.D., Munch, S.B., Thorrold, S.R., and D.O. Conover. 2009. Chemical signatures in the otoliths of a coastal marine fish, Menidia menidia, from the northeastern United States: spatial and temporal differences. Marine Ecology Progress Series 384:261-271.
Walther, B.D. and S. R. Thorrold. 2008. Continental-scale variation in otolith geochemistry of juvenile American shad. Canadian Journal of Fisheries and Aquatic Sciences 65:2623-2635.
Elsdon, T.S., Wells, B.K., Campana, S.E., Gillanders, B.M., Jones, C.M., Limburg, K.E., Secor, D.H., Thorrold, S.R., and Walther, B.D. 2008. Otolith chemistry to describe movements and life-history parameters of fishes: hypotheses, assumptions, limitations, and inferences. Oceanography and Marine Biology: An Annual Review 46: 297-330.
Walther, B. D., and S. R. Thorrold. 2006. Water, not food, contributes the majority of strontium and barium deposited in the otoliths of a marine fish. Marine Ecology Progress Series 311:125-130.