Stream invertebrate communities of Campbell Island

Invertebrates at 20 sites on 19 Campbell Island streams were sampled over the Austral summer of 1996/97. Twelve of the 16 benthic invertebrate taxa known from the island were collected. The most abundant group was the Crustacea, which included an isopod (Notidotea lacustris) and two amphipods, one belonging to the family Eusiridae and one to the suborder Gammaridea. Five species of Diptera were found (three chironomids; Orthocladiinae sp., Chironominae sp. and Maoridiamesa insularis, as well as an empidid and a simuliid Austrosimulium campbellense). One trichopteran, the hydroptilid caddis Oxyethira albiceps and two plecopteran species Rungaperla campbelli and R. longicauda and unidentified Oligochaetes were also collected. In general, Campbell Island streams are stable, deeply incised, have unusually high salinity from wind-blown sea spray and a unique benthic invertebrate fauna. With the exception of high altitude streams with large boulders which had invertebrate communities dominated by Crustacea and the endemic stonefly of the genus Rungaperla, none of the measured environmental variables or geographic location could explain the distinctive communities found. The species-poor stream fauna and the absence of many invertebrate families commonly found on mainland New Zealand appears to be related to the extreme isolation and geological history of the island.