Registro de Macrobrachium olfersii en un arroyo temporal de San Carlos, Guaymas, Sonora, México

On September 3rd 2009, tropical storm Jimena hit Guaymas, Sonora where it remained stationary for 36 hours uninterrupted producing 720 mm of rain, surpassing the annual state average. Because of the storm, some streams were formed over ancient basins, running down from Sierra El Aguaje, attracting the native fauna. Because of the atypical situation, the aim of this work was to search for species that had not been cited in the scientific literature for that region. With that purpose, a sampling expedition was conducted along the recently developed stream around La Marina Bridge, in San Carlos, Sonora. Two Macrobrachium olfersii specimens were collected: 1 ovigerous female and 1 male. The collected specimens are the first reported for the species in this area of Sonora, besides being the northern most record along the Pacific coast known to date.