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Benthic Invertebrates (Stream bugs)

damselfly in surrey

Benthic invertebrates are tiny organisms found living on the bottom of water bodies. Over 95% of all animal species are classed as invertebrates - or animals without backbones. Some examples are flies, slugs, leeches, beetles, bugs, worms, and crayfish.

Benthic invertebrates show stream health

Since 1998, the City has completed regular benthic invertebrate sampling in the spring and fall of each year on many local Surrey streams. We started in Spring 1998 with 12 sites. We now collect data at 40 monitoring locations across the city as shown on our sampling site map. This expansion gives us access to information from the vast majority of Surrey's creeks and streams.

This sampling helps determine the overall stream health, and helps monitor the changes in health of the stream from year to year, due to natural and human induced changes in the catchment. These organisms are good indicators of stream health because they:

  • live in the water for all or most of their life cycle
  • stay in areas suitable for their survival
  • differ in their tolerance to types/amounts of pollution, steam flow changes and changes in background water quality
  • often live for more than 1 year, allowing temporal patterns to be observed

Because we examine the presence and absence of these organisms at any particular sampling event, and over time, we're able to determine many indices that can be weighted. This educates us on the health of the upstream watershed, while looking at positive and negative natural- and human-induced changes/impacts.

Contact the Engineering Department, Environment Section at 604-592-6936 for details or data from Surrey's benthic invertebrate studies.