It is imperative to understand population processes of species of concern if we are to effectively conserve them. Often it is possible to study a population in the field to gain a better understanding of the processes driving the trajectory of its growth or decline. Many times it is not possible to conduct field studies on certain aspects of a species' life history for one reason or another. In these cases simulation models are useful to gain insight into population dynamics. I have used data from field studies, simulation models, and a combination of both approaches to explore population-level processes.
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For my most recent population studies involving tricolored blackbirds, please see Current Research
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Population Ecology
Recently, through work with the Black Duck Joint Venture, USGS, and Auburn University, we characterized the full annual cycle of American Black Ducks using a system of equations. We examined 60 years of band recovery data to determine how the birds should move about the continent in our model. We then used these two studies to explore the seasonal effects of density dependence on recruitment and survival for Black Ducks. Combined, these simulation and field based studies can show us when and where conservation action may provide the best benefit for this species.
For another recent study, in collaboration with members of the Jensen, Lockwood and Fefferman labs at Rutgers University, we examined the effects of fishing on a sex-changing species. Many comercially and recreationally important species (many grouper species, baramundi, black sea bass, and many others) are hermaphroditic. Our model used a species that was female first (protogynous) with flexibility in its timing of sex change, meaning it will change sex when it is most beneficial to do so. We used a game theory model to describe when a female changed to male, and embedded this behavioral model within a standard population model. We then simulated different life history parameters and a wide range of fishing pressure to determine how a sex changing stock responds to fishing when compared to a non-sex changing stock. The manuscript from this work was selected as an Editor's Choice paper by ICES Journal of Marine Science.
Photo by Bill Hubick.
Photo by Orion Weldon
