Biodiversity of freshwater and estuarine communities in lower Pearl Harbor, Oahu, Hawaii with observations on introduced species

Englund, R; Preston, D; Wolff, R; Coles, SL; Eldredge, L; Arakaki, K

Many species of aquatic organisms have been introduced into Pearl Harbor¿s streams, wetlands,and estuarine areas, altering the species composition of the aquatic fauna. This study, the first comprehensive inventory of the non-marine areas of Pearl Harbor, has found that introduced species comprise the dominant portion of the biota in the estuaries and streams of Pearl Harbor. The lower portions of Pearl Harbor streams, springs, and wetlands are now dominated both in total biomass and in total numbers by introduced species. The effects of introduced species vary widely, with fish species such as mosquitofish, suckermouth catfish, tilapia, and other cichlids suspected of causing the disappearance of many native aquatic species. The effects of introduced species such as dragonflies and damselflies appear to be more benign, as they have not been found to displace native species. A total of 329 species in 8 phyla were collected and identified in the estuarine and riparian habitats of Pearl Harbor. Of these 329 species, only 21% were native while 60% were introduced with the remainder (19%) being species of ndetermined origin. Terrestrial arthropods found in riparian zones adjacent to aquatic habitats were also collected, as these insects are a major dietary component for some fish species. If terrestrial arthropods found in riparian areas are excluded, 192 aquatic species were identified in the lower reaches of Pearl Harbor streams and wetlands. For these aquatic species, introduced species still dominated with 47% of the species recorded, while only 33% were native (endemic or indigenous) and the balance (20%) undetermined. Arthropods (mainly insects) constituted nearly 61% of the species collected in Pearl Harbor estuarine habitats. Other important groups found in Pearl Harbor estuaries included vertebrates (22%), mollusks (8%), and worms (7%). Minor components of the fauna collectively constituted only 2% of the species found, and included cnidarians, platyhelminthes, nematodes, and sipunculans. A new species of aquatic mite, Eupodes n. sp., was found in Pouhala Marsh during these surveys. In addition, two new introduced species were found during this study--a species of fangtoothed blenny (Omobranchus ferox) and an estuarine hydrobiid snail (Pyrgophorus cf. coronatus) introduced from the Caribbean. A new Oahu Island record was that of an introduced aquatic plant, Vallisneria americana. Introduced aquatic vertebrates and invertebrates found in Pearl Harbor have no predominant geographic origin, with species originating fairly evenly from North and South America, Asia and the western Pacific, with smaller numbers of species originating from Africa.

Biodiversity of freshwater and estuarine communities in lower Pearl Harbor, Oahu, Hawaii with observations on introduced species

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