Benjamin D. Walther
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Assistant Professor, Department of Marine Science Research Assistant Professor, Marine Science Institute
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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. Research Interests 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). Selected Publications 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. |