Effects of land use on native fish communities in east coast streams of the North Island of New Zealand

Abstract

The community structure, density, and biomass of native fish species was determined for first‐ to second‐order streams draining mature pine, native forest, and pasture catchments in seven, North Island, New Zealand, east coast rivers or streams. Multiple‐pass electric fishing was used to determine fish densities, and differences in fish community structure between land uses were detected using non‐metric multi‐dimensional scaling analysis. Species responsible for changes in fish community structure were identified by comparing species densities between land uses. Six fish species occurred commonly within each drainage system and although there was no difference in fish community structure between streams in native or exotic forest, differences occurred between the fish communities of forested and pastoral streams. Pastoral streams contained more shortfinned eels (Anguilla australis), more inanga (Galaxias maculatus), and fewer banded kokopu (Galaxias fasciatus) than forested streams. Fish biomass was also higher in pastoral streams. We concluded that the type of forest (mature exotic pine versus mixed‐species indigenous) had little effect on the native fish populations, but that pasture supported an increased fish density and biomass due mainly to increases in shortfinned eels. There were fewer banded kokopu in pasture than in forested streams, but exotic forest streams contained as many banded kokopu as native forest streams.

Keywords:

• native fish
• density
• biomass
• community structure
• species diversity
• land use
• pine forest
• native forest
• pasture