Doctor of Philosophy (Ph.D.)
Virginia Institute of Marine Science
Romuald N. Lipcius and Grace S. Chiu
Mary C. Fabrizio
The blue crab (Callinectes sapidus) is a commercially and ecologically importantspecies found along the Atlantic coast of North and South America. These crustaceans play a critical role in coastal ecosystems, serving as both predators and prey in the food web. The blue crab supports a major fishery in Chesapeake Bay, where the species is a cultural icon. Juvenile blue crabs, the smallest and most vulnerable size classes of individuals, are reliant upon structurally complex habitats. Population dynamics of this species are therefore influenced by spatiotemporally fluctuating environmental variables, such as habitat availability. Understanding blue crab ecology is essential for managing their populations sustainably and maintaining the health of their habitats. The primary aim of this dissertation was to quantitatively evaluate the contributions of several widely distributed habitats to blue crab population dynamics in Chesapeake Bay. Empirical valuation of nursery habitat effects on blue crab population dynamics can (i) estimate the optimal extent of habitat required for the long-term sustainability of blue crab fisheries, (ii) quantify how changes in habitat extent will affect blue crab populations, such as alterations due to climate change, and (iii) inform ecosystem-based fisheries management (EBFM) decisions, as a complement to stock assessments. Here, I present four separate but interrelated studies examining habitat-specific demographic rates at multiple spatial and temporal scales. These studies involved a combination of survey data, mensurative and manipulative field experiments, and complex population dynamics models. Chapter 1 evaluates nursery habitat contributions to blue crab population dynamics by examining relationships between juvenile blue crab distributions and multiple environmental variables in three tributaries—the York, James, and Rappahannock rivers—at broad spatial (regional) and temporal (decadal) scales using fisheries-independent survey data and digitized GIS maps of habitat distributions. Chapter 2 examines fine-scale spatiotemporal (i.e., 10s of km2 over biweekly intervals) variation and ontogenetic shifts in juvenile blue crab densities in salt marsh edge, seagrass, shallow detrital habitat, and unstructured habitat under a suite of physical and biological parameters in the York River. Chapter 3 expands on these findings to examine the mechanistic basis for ontogenetic habitat shifts by evaluating differential abundance and survival of juvenile blue crabs across three size classes in salt marsh edge, seagrass, and unstructured sand habitat, with specific attention to effects of refuge, turbidity, and postlarval supply. Finally, Chapter 4 integrates population-scale indices of abundance from two major fisheries-independent surveys with time-series of habitat data to assess the influence of seagrass species on blue crab population dynamics at the scale of Chesapeake Bay.
© The Author
Hyman, Alexander C., "Empirical Valuation Of Primary And Alternative Nursery Habitats For The Blue Crab Callinectes Sapidus In Chesapeake Bay" (2023). Dissertations, Theses, and Masters Projects. William & Mary. Paper 1697552696.