UC San Diego
Improving management of exploited species with knowledge of life history and spatial processes
- Author(s): Stock, Brian
- Advisor(s): Semmens, Brice X
- et al.
My dissertation is motivated by the desire to achieve balance between conservation and exploitation of marine populations (i.e., sustainable harvest). Navigating between the extremes of preservationism and extinction with any confidence requires that we assess the status of exploited populations and the ecosystems that support them. Single-species, equilibrium-based fisheries management has been somewhat divisive, with proponents giving it credit for largely ending overfishing and critics citing spectacular examples of failing to prevent fisheries collapses. One of the primary critiques of traditional fisheries management is that it ignores important ecological realities, such as variability in vital population rates stemming from: 1) environmental variability, 2) spatial population structure and movement, and 3) species interactions.
My dissertation focuses on improving management of exploited species by adapting models to species' life history, with particular emphasis on the effect of spatial structure. Chapter 1 improves stable isotope mixing models, used to estimate animal diets, by introducing a new statistical structure makes more ecologically-realistic assumptions about the relationship between predator and prey isotope signatures. We demonstrate that this new parameterization implicitly estimates predators’ consumption rate and outperforms existing models. Chapter 2 considers how fisheries bycatch species' life history traits, use of space, and catch rates affect models used to predict spatiotemporal bycatch risk. We find that machine learning approaches (e.g. random forests) outperform recently developed semiparametric spatial models for the purpose of generating fisheries bycatch predictions to be used in dynamic management tools. Chapter 3 develops assessment methodology for protected fish species that form spawning aggregations, a life history strategy particularly vulnerable to overexploitation. While no catch or effort data can be collected from the protected population, we demonstrate the efficacy of length-frequency time-series collected in situ to detect recruitment spikes and population recovery. Chapter 4 investigates the mortality and 3-dimensional dispersal of eggs and larvae from a Nassau Grouper (Epinephelus striatus) spawning aggregation, and discusses the likelihood of large self-recruitment events.