A new report has shown a sharp decline in fresh water quality since the year 2000. Increasing urbanisation and more intensive farming are blamed.
The report was done by a Massey University for the Ministry for the Environment: 22,500 records of fish communities nationally were analysed and found to show significant decline over the past 40 years.
Freshwater ecologist Dr Mike Joy says the most dramatic fall in fish sightings has been in waterways adjoining pastoral and urban sites.
Dr Joy says this is linked to increased sediment and nutrient levels in rivers and streams, revealed in monitoring done by the National Institute of Water and Atmospheric Research.