Patterns of temporal occurrence of brachyuran crab larvae at Saco mangrove creek, Inhaca Island (South Mozambique): implications for flux and recruitment

Temporal patterns of larval occurrence of brachyuran taxa weredescribed from Saco mangrove creek, Mozambique, based on planktonsamples. Brachyuran larvae were collected hourly in four 24h cycles during neap and spring tidal periods at a fixed station,in November 1997 and February 1998. Results indicate a semilunarcycle of larval release activity for most species. Newly-hatchedstages of sesarmids showed a peak occurrence in post-crepuscularebbing tides, Macrophthalmus spp. and Uca spp. showed highestdensities during ebbing tides at night. Dotilla fenestrata andPinnotheridae, in spite of showing a semilunar pattern, didnot display significant differences between day and night. Mostmangrove taxa showed thus a clear larval exportation behaviourduring ebb tides, with little return during the following floods,with varying degrees of dependence on the diel period. Megalopaewere restricted to the night period, and highest values wereobtained during spring tidal periods. However, maximum valuesof megalopae were obtained both during flood and ebb periods,contrary to most previous studies. This is interpreted as abi-directional transport of non-competent megalopae into andfrom the mangrove area.