Competition between range-expanding green porcelain crabs (Petrolisthes armatus) and eastern oysters (Crassostrea virginica) in coastal Georgia

REU Fellow: Megan Novak, University of North Florida

Mentor: Dr. John Carroll

Invasive green porcelain crabs are present on eastern oyster reefs in high densities in the South Atlantic Bight. Although they have been shown to affect native fauna present on the reefs in both positive and negative ways, the specific mechanisms by which the crabs affect oysters are unknown. Both species are suspension feeders, but it is not clear whether or not they consume the same types of food. The effect of green porcelain crabs on eastern oyster spat growth and survival was tested in two experiments – one to test physical interaction between the two species, the other to test for competition for food resources. Physical presence of the crabs had a significant negative effect (p˂0.001) on the survival of the oyster spat. The oysters in the physical interaction experiment did not grow in either the controls or the treatments. When crabs shared food resources but did not physically interact with the oysters, spat growth in crab treatments was lower than the controls, but these effects were not significant. In that same experiment, there was no significant effect of the crabs on the survival of the spat. A comprehensive understanding of the interaction between invasive green porcelain crabs and native eastern oysters in Georgia is essential in order to make informed decisions about oyster reef conservation.