First record of Acanthurus monroviae (Osteichthyes: Perciformes: Acanthuridae) in southern Portugal, with notes on its recent distributional spread in the northeastern Atlantic and Mediterranean

The present study reports the first record of the Monrovia doctorfish, Acanthurus monroviae (Steindachner, 1876) in the Algarve coast (southern Portugal). A female (257 mm TL) was caught 21 April 2016 off the beach of Olhos d’Agua by a small-scale fishing boat operating bottom-set gill nets at approximately 15 m depth. Morphometric and meristic parameters of the specimen are reported and compared with previous records of A. monroviae. This is the second occurrence of this tropical fish species in Portuguese waters and the second northernmost capture ever reported for the northeastern Atlantic. The present record is an additional example of tropicalisation of the ichthyofauna in temperate waters by a thermophilic tropical species. Indeed, although not established in the study area, A. monroviae found a suitable seawater temperature regime in southern Portugal and further expanded its distributional range along the Iberian coasts. For biogeographic purposes, all reported occurrences of this species in the northeastern Atlantic and Mediterranean (including very recent records and sightings) are compiled and mapped.