The intertidal mudflats of Barr Al Hikman, Sultanate of Oman, as feeding, reproduction and nursery grounds for brachyuran crabs

Brachyuran crabs are an important ecological and economical, yet often unstudied aspect of intertidal mudflats of the Arabian Peninsula. Here we provide baseline density estimates of crabs at the relatively pristine intertidal mudflats of Barr Al Hikman (Sultanate of Oman) and provide information on their life cycle and habitat preference. Across the winters of 2012-2015 crabs were sampled on a grid covering the entire intertidal depth gradient. 29 species were found and average densities varied between 12 and 54 crabs/m(2). Deposit-feeding and herbivorous crabs were the most abundant species across all winters. Size frequency data and the presence of ovigerous females show that most crabs species reproduce in the intertidal area.P. segnis, the most important crab for local fisheries, was found to use the intertidal area as a nursery ground. We analysed the relationships between the two most abundant crab species,Macrophthalmus sulcatusandThalamita poissoniiand the environmental variables: seagrass density, tidal elevation, median grain size and sediment depth using Random Forest models. The predictive capacity of the models and the relative importance of the environmental predictors varied between years, but crab densities in general were positively associated with seagrass density, presumably because seagrass offers feeding habitat.