Simple modeling solutions for complex conservation problems

Species are going extinct at a rate far higher than pre-human levels. For many species that are endangered, basic biological information may not be available to conservation managers. In these situations, mathematical models can be useful in providing insight into the biological requirements of species and to make credible predictions about how management actions may. Here, I present three modeling techniques that help to show the efficacy of management actions (Chapters 1&2) and the effects of exploitation on species with unique life histories (Chapter 3). I show that combining two foundational elements of ecological theory (matrix population models and functional responses) into one coupled model provides a flexible approach to determining the best conservation strategy to recover prey under threat from an invasive predator. I suggest a simple addition to existing population viability models that allows managers to calculate the probability that management action will improve the status of a declining population and the probability that enacting management will be no more effective than doing nothing. I illustrate the method by using previously published population viability analyses. For some management situations, doing nothing may be just as effective as enacting an expensive management strategy. Calculating these probabilities can provide tangible ways to balance risk and reward when making management decisions. Last, I present a game theoretic approach to model the behavior of sex changing fish. I produced estimates of maximum sustainable yield (MSY), biomass at maximum sustainable yield (BMSY), and sex ratio for sex changing and non-sex changing stocks at different levels of fishing pressure and varying fertilization rates. The results suggest that sex changing stocks may be as robust to fishing as non-sex changing stocks. This game theoretic approach to evaluating hermaphroditic stocks can accommodate a wide variety of sex changing cues and allows a flexible model for understanding the effects of exploitation on hermaphroditic stocks. Models have proven useful in many conservation situations and will continue to aid managers. I have shown that simple additions to traditional models can provide more insight on the efficacy of management and how unique breeding behavior may be incorporated into conservation decision-making.Ph. D.Includes bibliographical referencesby Orin J. Robinson Jr