The ecoregion has a total known number of 105 non-indigenous and cryptogenic (obscure or of unknown origin) species. The majority (57 species) arrived between 1950 and 1999. Since 2000, a total of 33 new species have been recorded in the Azores. The annual rate of discovery of non-indigenous species increased from 1.1 per year between 1950 and 1999, to 2.1 per year between 2000 and 2015 (see Figure 5). The dominating taxonomic groups are mollusca, rhodophyta, and chordata.
Shipping, particularly through ballast water and the biofouling of hulls, is the main species introduction vector, followed by water currents (natural spread from neighbouring areas).
Figure 5: Average annual rate of new non-indigenous and cryptogenic species discoveries in the Azores ecoregion between 1950 and 1999, then between 2000 and 2015 (source: AquaNIS, 2018).