During our rapid assessment surveys, we encountered few introduced marine invertebrates on Hawaiian coral reefs.

A total of 26 introduced or cryptogenic (NIS) species were found in ca. 120 hours total search time at 41 coral reef sites on the five most populated Hawaiian Islands. The maximum number of NIS that occurred at any site was 6, and more than half of the sites had less than 3 NIS (or less than 2 if introduced fish are excluded). NIS comprised no more than 10% of the total taxa identified at any sites and were less than 2.5% at over half the sites.

The only abundant NIS invertebrates were the octocoral Carijoa riisei at Mala Wharf on Maui, the Orange Keyhole Sponge Mycale armata and the Featherduster Worm Sabellastartes spectabilis in Kaneohe bay. Near the survey sites in Kaneohe Bay, Mycale armata appeared invasive as it overgrew patches of live coral at several locations of Coconut Island (see picture below). Both Carijoa riisei and Mycale armata are, under certain environmental conditions, potentially invasive alien species which may monopolize habitat and overwhelm native species with their growth, and both species should be watched for and monitored for their impacts on coral reefs.