Meeting Abstract

49.1  Jan. 6  the effect of summer storms on the recruitment success of fiddler crabs BRODIE, R. *; GODLEY, J.; Mount Holyoke College rbrodie@mtholyoke.edu

The estuarine fiddler crabs, Uca minax, U. pugnax and U. pugilator, have complex life cycles spanning vastly different salinity regimes. Larvae are spawned in estuaries and travel to the coastal ocean where development takes place; after metamorphosing to the megalopal stage, fiddler crabs reinvade estuaries where they settle and metamorphose. In the coastal ocean, larvae experience relatively stable physical conditions, however, upon reinvading estuaries they are exposed to great fluxes in salinity and temperature. In this study, we measured shifts in the salinity regime caused by storm events, and determined the impact of these changes on species frequencies of megalopae from three Uca species in the water column and of their recently settled juvenile crabs on the benthos along a salt marsh creek in South Carolina. For megalopal stages in the water column, we found that the relative proportions of the three species changed significantly along salinity gradients and in response to storm events. When the salinity regime normalized, species frequencies for megalopae returned to pre-storm proportions. Only U. minax megalopae were present in the water column during a storm event, while U. pugnax had been the most abundant species in the water column prior to the storm. Settled juvenile crabs of all three species were more resilient than megalopae to flash salinity changes associated with summer freshets. Our results show that the duration and severity of salinity change are important variables impacting the presence of these Uca species in the water column and suggest that the physiology and behavior of the megalopal stage strongly influence where populations occur within estuaries.