Submerged aquatic vegetation (SAV), such as seagrasses, within Chesapeake Bay provide protection and resources for fishery species like the blue crab Callinectes sapidus (Duffy & Baltz 1998). In Chesapeake Bay, seagrasses have been declining since the 1960s and 1970s due to both anthropogenic and natural disturbances (for example, Orth & Moore 1983). Increased fragmentation of and decreased shoot density within seagrass beds may negatively impact the recruitment of blue crab postlarvae that use seagrasses as nursery habitat (Stockhausen & Lipcius 2003). In areas where seagrasses have declined, macroalgae may provide valuable habitat for organisms like the blue crab. Gracilaria vermiculophylla is an exotic, coarsely branching, red macroalga originating from the Western Pacific (Ohmi 1956) that has colonized shallow coastal areas of North America and Europe (Bellorin et al. 2004; Freshwater et al. 2006; Thomsen et al. 2006a, b, 2007; Gulbransen et al. 2012; Miller 2012) and is found in lower Chesapeake Bay. It is possible that this exotic alga may fill some of the ecological roles of seagrasses in these areas where they have declined (Rodriquez 2006). Because it is a structured nursery habitat, G. vermiculophylla provides refuges for juvenile blue crabs and other species that require structure (Beck et al. 2001; Lipcius et al. 2007; Thomsen 2010). Juvenile crab survival is as great or greater in G. vermiculophylla compared to Zostera marina (the dominant seagrass in lower Chesapeake Bay) or unvegetated habitat (Johnston & Lipcius 2012).
My dissertation research aims to determine the value of G. vermiculophylla as a nursery habitat for juvenile blue crabs in the York River, a tributary of lower Chesapeake Bay. My research involves exploratory surveys to determine where the alga is and how much there is at randomly selected sites, how many juvenile crabs are using the alga as habitat compared to seagrass, and differences in prey resources between the habitats. Other field and laboratory studies focus on habitat preferences of juvenile crabs as well as growth rates. Finally, the development of a system of equations to describe habitat use of juvenile crabs will allow me to simulate how the changing nursery habitat landscape in Chesapeake Bay will impact juvenile crabs and, thus, the adult blue crab population.
The key stakeholder groups that might benefit from my research, particularly the model, are managers and watermen in the blue crab fishery. The commercial blue crab fishery in Chesapeake Bay is tightly controlled by managers, but management tends to focus only on mature crabs (those that can be fished). There seems to be a disconnect between the way blue crabs are managed and the ecology of the species in that juvenile crabs and their habitat requirements are often ignored by managers. My work seeks to link habitat information with population information, which may lead to a better-informed stock-recruit model for blue crabs in Chesapeake Bay and, therefore, better-informed management strategies that will allow watermen to continue to harvest blue crabs in the future.
To better communicate my model to all audiences, but particularly to managers and watermen, I will create a series of slides using a tool like Prezi (https://prezi.com/) that will help explain my model step-by-step using pictures and simple graphs connected to each variable within the equations. Since the equations of my model are very similar to each other, I will likely focus on one and then zoom out to show the entire model. Hopefully this will allow the audience to understand what the model is doing without getting bogged down in terminology. This also will reduce the loss of interest that many audiences have when presented with a slide of 10 equations. I plan to present this initially at the 2016 VA Sea Grant Participants’ Symposium alongside a poster of related research.
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