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Temporal and land-cover trends in freshwater fish communities in New Zealand's rivers: an analysis of data from the New Zealand Freshwater Database - 1970 - 2007

Publication date:  March 2009
Publication reference number:  CR 62

This report summarises changes in fish communities in New Zealand rivers, including changes in relation to different land uses. This is the first time this data has been analysed and reported on at a national level. The report adds important information to existing Ministry reporting on river water quality and informs New Zealanders of the state of New Zealand’s rivers and any changes over time.

Key findings

  • Rivers surrounded mostly by native vegetation have more fish species and healthier fish communities than rivers dominated by pastoral or urban land-cover. We cannot be certain about the reasons for this difference, although it is likely to be related to both declines in water quality and habitat condition (eg, in-stream obstacles to fish passage) that are associated with human activities on the land.
  • Overall, at a national scale, the health of fish communities declined between 1970 and 2007, especially over the last decade (2000 to 2007). The biggest decreases in the health of fish communities were in rivers in mostly pastoral (farming) or urban areas.