Doctor of Philosophy (Ph.D.)
Virginia Institute of Marine Science
Romuald N. Lipcius
Most benthic invertebrates and reef-associated fish undergo a dispersive, planktonic larval stage prior to settlement and metamorphosis into the juvenile and adult stages. In some species, settlement may be decoupled from adult abundance at local spatial scales if hydrodynamic conditions or larval behavior do not promote local retention. Similarly, spatial variability in postsettlement mortality or secondary dispersal by juveniles and adults may decouple spatial patterns of adult abundance from those of settlement. as a consequence, spatial patterns of settlement and adult abundance may be functionally related in a complex fashion. Whether biotic/environmental factors control spatial patterns of abundance may have profound implications for conservation of exploited benthic marine species, particularly when patterns of exploitation are themselves spatially structured as they are under management by marine reserves. As part of this dissertation, a spatially-explicit population dynamics model for the Caribbean spiny lobster in Exuma Sound, Bahamas was developed. The model is stage- and age-structured, and features dispersal of larvae from hatching sites via advection by hydrodynamic currents and diffusion, active migration of postlarvae into shallow nursery habitats, density-dependent survival and dispersal of benthic life-history stages (juveniles and adults), size-specific fecundity, and spatially-explicit exploitation rates. The population dynamics model was used heuristically to investigate the joint effects of reserve design (i.e., size, location, number), exploitation, population regulation and larval dispersal via hydrodynamic currents on population abundance and fishery yield. Principal findings were that fishery yield and larval production were idiosyncratic functions of reserve size, substantially influenced by interactions between current patterns and reserve location. Also, management strategies which implemented a single large reserve outperformed those using a network of small reserves, a reduction in total effort, or no action whatsoever. Results support the efficacy of marine reserves as a tool for rebuilding overexploited marine populations and creating sustainable fisheries. However, haphazard reserve creation may lead to a false sense of security, and poorly-designed reserves can perform worse than taking no action at all. Thus, designing successful marine reserves requires knowledge of local and regional patterns of hydrodynamic transport and larval dispersal, as well as other species' life-history characteristics.
© The Author
Stockhausen, William T., "The impact of marine reserves on exploited species with complex life histories: a modeling study using the Caribbean spiny lobster in Exuma Sound, Bahamas" (2001). Dissertations, Theses, and Masters Projects. Paper 1539616923.