Unusual upstream extension of Callinectes sapidus Rathbun, 1896 (Crustacea, Portunidae) into the Lower Drâa, southern Morocco

The Atlantic blue crab Callinectes sapidus Rathbun, 1896, a euryhaline species native to the western Atlantic, is being reported with increasing frequency along Morocco’s Mediterranean and Atlantic coasts. Here, we document a notable new record from a temporarily isolated guelta (pool) within the Lower Drâa River channel, located approximately 52 km upstream from the river mouth. This photographic observation concerns an exceptionally large adult (estimated carapace width >20 cm) found alive in a residual pool of clear water formed by desiccation of the main channel. It is the most inland record of C. sapidus in Morocco and, to our knowledge, in Africa, within an arid fluvial system. This single-individual record most likely reflects active upstream migration during a period of hydrological connectivity followed by stranding, rather than an established inland population. Nevertheless, the co-occurrence of this individual with cichlid fish (Coptodon spp.) raises concerns regarding potential predation on their early life stages. We consequently recommend focused resampling, measurement of environmental parameters (including salinity, temperature, and dissolved oxygen), diet analysis, and genetic assignment to identify provenance and evaluate ecological risk.