The 287 alien marine invertebrate species make up about 7 % of the known marine and brackish water invertebrate fauna in the Hawaiian Islands (4099 species). Arthropods have been the most successful marine invaders, with 71 suspected alien crustacean species, while 53 alien molluscs have made it to Hawaii. Due to the large number of alien marine invertebrates in Hawaii and the limited amount of information known for most of them, we can highlight only a few of these nonindigenous species in this guidebook.

The greatest number of introduced marine invertebrates have probably arrived to Hawaii through hull fouling, but many may have also arrived with solid ballast and in ballast water.

We consider 201 species (70%) to be introduced, and 86 species (30%) cryptogenic (not demonstratively native or introduced). Two hundred forty eight (87%) have become established, 15 (5%) arrived but failed to become established, 6 (2%) were intercepted, and the population status of 18 species (6%) is unknown.

The nonindigenous invertebrate species in the Hawaiian Islands are primarily of Indo-Pacific/Philippines Islands region origin. A surprising number of species from the tropical western Atlantic/Caribbean region have invaded Hawaii as well.