Summary

Description

A survey of the marine communities of Midway Atoll harbor and surrounding lagoon was conducted at 12 sites from September 5 to 9, 1998. The primary focus of these surveys was the invertebrates of the fouling communities present on artificial substrates. Occurrence of reef fishes at each site was also recorded, and algae was collected and identified from four stations. A total of 444 taxa were identified (47 algae, 316 invertebrates, and 81 fishes) from all stations. Approximately 250 invertebrate and 35 algae species are considered new records for Midway Atoll. All fishes observed were previously recorded from the atoll. Only three invertebrates identified in this survey are considered to be nonindigenous species in the Hawaiian Islands. One introduced bryozoan, Amathia distans, dominated the fouling communities at most stations where artificial substrates were available. Another introduced bryozoan, Schizoporella errata, was also common at the same stations. A non indigenous barnacle, Chthamalus proteus, recently introduced from the Caribbean, was common on pier pilings inside Midway harbor. No introduced invertebrates were present in natural habitats. The introduced snapper, Lutjanus kasmira, was also present along the reef outside the lagoon. The threat to the native reef community by established non-indigenous species is considered minimal. The presence of these introduced species at Midway, especially Chthamalus proteus, suggests that vectors of future, potentially more deleterious introductions exist. Transport of these introductions was most likely as fouling on ship bottoms, but other sources of introductions, such as ballast water carried in ships, should be guarded against to protect the relatively pristine reefs of Midway Atoll.