Massive strandings and local perception highlight the extent of Rugulopteryx okamurae invasion on the Moroccan coast

Since its arrival on the Moroccan coast in 2017, no formal risk assessment has addressed the ecological and socio-economic impacts of the invasive macroalga Rugulopteryx okamurae, despite clear evidence of its threat to coastal habitats in the Strait of Gibraltar. This study provides updated insights of the invasion in northern Morocco, contributing to a better understanding of its expansion in the southern Mediterranean. Field surveys conducted between 2019 and 2022 documented widespread strandings of R. okamurae from Al Hoceima to Larache, with peak accumulations in M'diq (358 t FW, 2019) and Asilah (242 t FW, 2021). Interviews with local fishers revealed tangible socio-economic impacts, particularly in M'diq, where 91 % reported income losses related to the presence of the alga. Environmental data suggest that sustained sea surface temperatures, rarely below 15 °C and peaking at 26.9 °C, may have facilitated its proliferation. By highlighting both the ecological footprint and economic consequences of the invasion, this study provides essential baseline data to support future monitoring, risk assessments, and targeted management strategies in the region.