The CIESM Atlas of Exotic Species was the first attempt to provide a comprehensive, group by group, survey of recent marine "immigrants" in the Mediterranean, which is undergoing drastic and rapid changes to its biota. Many of these new species are of Indo-Pacific origin having reached the Mediterranean Sea through the Suez Canal: these so called "Lessepsian" migrants now contribute significantly to the biodiversity of the Eastern basin. With increasing attention paid to this phenomenon, invaders of other origin-notably from the tropical Atlantic realm- are now more frequently recognized as well, a result of a natural invasion through the Gibraltar straits or of introduction (accidental or intentional) by man.

The Atlas is a guide for researchers, environmental planners and non-specialists who are interested in or likely to encounter marine species that are not native to the basin. Because of observations and records of these new and often rare species the Atlas will expand as our knowledge on the distribution and ecology increases. The best way to inform you about the changing seascape is through a digital interactive format, which will enable us to quickly update information and allow instant feedback.

The Atlas consist of four volumes, each written by a group of specialists in their respective field. Individual species pages are designed to stand alone as information sheets with illustrations, diagonistic features, biological information, references and a distribution map for each exotic species. The CIESM task force experts will continuously review reliable evidence of new or confirmed records thus updating and expanding the Atlas.

Species considered for inclusion but rejected due to questionable records is listed in an appendix.