Invertebrates are animals that neither possess nor develop a vertebral column. They are an exceptionally diverse group, which include the insects, arachnids and molluscs. Of the 30,000 species of terrestrial and freshwater invertebrate that occur in the UK, several species receive protection under law or policy as a result of them being under threat.
Planning authorities may require an invertebrate survey to be undertaken where a development could affect important invertebrate habitat, including rivers or woodland, or a protected species of invertebrate, such as southern damselfly or fen raft spider. Invertebrate surveys are also used to assess and monitor the condition of our rivers, lakes and streams.
The first stage in conducting an invertebrate survey is to determine an appropriate technique based on both the objective of the survey and the physical nature of the habitat. Standard survey techniques include direct observation, hand searching, sweep netting, beating, pond netting, kick sampling and trapping. Specimens collected during surveys are either identified in the field or preserved for subsequent identification in the laboratory.
Once the survey is complete, the condition of invertebrate assemblages can be assessed using the Invertebrate Species-habitats Information System (ISIS). The results of aquatic invertebrate surveys can be used to evaluate waterbody health using the Biological Monitoring Working Party (BMWP) score, Average Score Per Taxon (ASPT) or River Invertebrate Prediction and Classification System (RIVPACS).