Patterns of distribution and association of freshwater fish in New Zealand

Abstract

Presence‐absence data for New Zealand's freshwater fish fauna were analysed for evidence of species interactions and of links with land‐use and geological patterns. Co‐occurrence patterns differed between site and regional levels. Native and exotic species had overlapping geographical distributions but tended to be segregated at the site level. Species‐area curves were developed for lotic and lentic sites which explained a small portion of the variation. Regressions involving land‐use and geological variables accounted for more variation. New Zealand catchments appeared to be under‐saturated with species compared to northern temperate catchments. Analysis of co‐occurrence patterns, where distributions overlapped, indicated relatively more negative associations between native andexotic species than among either group of species. The presence‐absence patterns of several native species were related to land use and geological factors. The conclusion from these analyses was that both land‐use changes and introductions of exotic species, particularly salmonids, have caused changes in the distribution of native fish species.