PARENT SESSION
Contributed Oral Session 84: Ecology of Marine and Intertidal Systems
Wednesday, August 10, 8:00 AM - 11:30 AM, Meeting Room 520 B, Level 5, Palais des congrès de Montréal
How Transient patches affect population dynamics: the case of hypoxia and blue crabs.
Aumann, Craig 1, Eby, Lisa2, Fagan, William 3, 1 University of Alberta, Edmonton, AB2 University of Montana, Missoula, MT3 University of Maryland, College Park, MD
ABSTRACT- Transient hypoxic patches, where patch characteristics change quickly relative to the timescale of the population or community involved, may have important consequences for the population dynamics of many estuarine species. For commercially important blue crabs (Callinectes sapidus), one hypothesis is that temporary reductions in habitat caused by hypoxia increase rates of cannibalism. A second hypothesis is that crab population dynamics are a result of food limitation caused by hypoxia-induced mortality of the benthos. To assess these alternative hypotheses and to determine whether population dynamics under transient patches differs from static patches, we developed a spatially explicit individual-based model of blue crabs in an hierarchical framework to connect the autoecology of crabs with the spatial and temporal dynamics of their physical and biological environments. The primary scenario considered examined the interactive effects of hypoxic extent versus static and transient patches. Static patches resulted in populations limited by egg production/recruitment while transient patches lead to populations limited by the effects of cannibalism/patch interactions. Crab survivorship was greatest for scenarios with the largest hypoxic patches which also had the lowest prey abundance. Nearly all crab mortality was accounted for by aggression - not starvation. Thus, we conclude that crab populations in typical estuaries are primarily controlled by increased density-dependent cannibalism resulting from temporary habitat loss and not food limitation.
Key words: callinectes sapidus, hypoxia, population dynamics, individual-based model