Sandy beach mole crabs (Decapoda: Hippidae: Emerita): A systematic review of the anthropic impacts, populations density, and conservation strategies

Emerita species (Scopoli, 1777; Crustacea: Decapoda: Pleocyemata: Anomura: Hippidae), commonly known as mole crabs, are specialized in burying and distributed in the swash zone of the Pacific, Atlantic, and Indian Ocean sandy beaches. This genus has received increasing attention in scientific studies owing to its ecological importance. It is used as a model species to evaluate the ecological state of communities and as a bioindicator of environmental health and quality. Here, we systematically reviewed the literature to understand how Emerita species are affected by anthropogenic activities and gathered records of its population densities. Two independent literature searches were conducted on anthropogenic impact and population density. Anthropogenic impacts were reviewed using 61 articles published between 1974 and 2023. The main anthropogenic impacts were physical changes (n = 19) and toxicity (n = 18). E. analoga, E. talpoida, and E. brasiliensis were the most studied species. Some anthropogenic impacts did not directly damage E. analoga and E. talpoida. E. analoga was more tolerant of certain types of impacts related to physical changes and toxicity. Lower densities of E. brasiliensis were associated with more urbanized beaches. Accessing data on annual cycles, density fluctuations, and population peaks is important to minimize the impacts on populations. In total, 42 articles reported surveys on population density or abundance in nine countries. E. brasiliensis exhibited the highest amount (n = 17) on the beaches in Brazil and Uruguay, followed by E. analoga (n = 13), in Chile and USA. A temporal reduction in the densities was observed for E. brasiliensis, primarily on beaches in Brazil, and E. talpoida. A global standardization of sampling and density and abundance data presentation is necessary for effective long-term assessments of Emerita species. This study synthesizes the impacts that have occurred on Emerita, highlighting potential threats to its conservation.