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River biology

Why we monitor river biology

Waikato Regional Council monitors river biology to determine the ecological health of rivers and streams in the Waikato region. Fish tell us more about habitat and water quality, as well as about how well migratory native fish can get access to streams from the ocean. Invertebrates are a key part of the biodiversity of all rivers and streams. They also form an important part of the food chain in rivers and streams, and can influence habitat quality by filtering water, churning up sediments and breaking down organic material. Invertebrates are medium term indicators of stream health and integrate conditions over time prior to sampling. River biology is therefore less affected by small rainfall events than traditional water quality parameters such as faecal coliforms or E. coli which vary temporally in relation to rainfall. 
Waikato Regional Council’s stream invertebrate monitoring programme:

Stonefly larva

  • reports on the current condition of the state of the regions waterways as a per cent of waterway length in each condition class.
  • determines ecological condition trends over time at long-term monitoring sites
  • identifies environmental factors related to stream health
  • helps develop policies that mitigate adverse effects on stream ecosystems
  • provides information for assessing the effectiveness of restoration and mitigation activities
  • helps achieve Waikato Regional Council’s responsibilities for state of the environment reporting
  • helps assess the performance of policies in the Regional Policy Statement.

What's happening?

The invertebrate sampling shows us that ecological health of streams and rivers is better in some parts of the Waikato region than in others. This is mainly because of the greater intensity of land use in parts of the region with large areas of lowlands and developed hill-country. 

>>Find out more about these data and trends

More information

More detail on this indicator, including how and where Waikato Regional Council collects this information, is available in the Technical Information page.

Useful links

Find out more about the state of our region’s rivers and what aquatic plants and animals live there.

For more information on aquatic species identifications and distributions see the NIWA and Landcare Research websites.

The United States Environmental Protection Agency website provides information on rapid bioassessment protocols for use in streams and wadeable rivers.

When this indicator is updated

This indicator is updated every three years

Contact at Waikato Regional Council

Aquatic Ecologist (invertebrates) - Science and Strategy Directorate 


  1. Calculated for both hard-bottomed and soft-bottomed sites relative to hard-bottomed reference sites because there are few lowland soft-bottomed reference streams in the region. Further work is currently underway to determine the expected difference between reference site conditions for these two types of stream, and how this influences condition classes. We are also developing condition classes for habitat quality and algal and plant cover.
  2. Excludes algal-piercing Hydroptilidae.