A11. Riparian Invertebrate Survey

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1 Objectives

Assess the quality and diversity of the corridor habitats along watercourses using riparian beetles.

2 Method summary

To get an overview of the diversity of riparian beetles a combination of three techniques: hand searching, excavation and pitfall trapping is recommended (Natural England, 2017). Four sampling stations close to each other (200m), usually on sand or shingle bank and associated habitats, should be surveyed. Each one should be surveyed for a one-hour hand-searching, completed by 20 minutes excavation (only on sand and shingle bars). This is complemented by pitfall traps which are buried for 2 weeks within the defined sampling station.

Sample station: a stretch of river and its associated riparian habitat, including: eroding banks, edges of backwaters, vegetated sand and shingle, riparian woodland, stretches of emergent vegetation, woody material etc.

Hand-searching method: for each station, 6 searches of 10minutes are undertaken targeting the specific habitats presents. The 10 minutes includes the time to prepare equipment and transferring individuals to collecting tubes. Specific techniques are advised according to the habitats (please see protocol)

Excavation: Following the Sadler and Petts (2000) method, the operator digs a 1m² area, located 1 or 2 meters from the river edge, down to the water table. The sides of the excavation are gradually collapsed down into the water and floating invertebrates are collected. Method should last between 15 and 20 minutes.

Pitfall trapping: Based on Sadler and Bell (2000), the surveyor buries ten small plastic cups, c. 10cm diameter, in the sediment/soil, so that the rim is flush with the surface. These are filled one third full of a 50:50 mixture of propylene glycol. and water, with a small amount of detergent added to break the surface tension. Pitfall traps are placed in the riparian zone, at least 2m apart in each of the habitat types detected.

Survey should be performed between the first week in May to the last week in June, with mid-May to mid-June being optimal as it corresponds to the peak of beetle activity.

3 Advantages

  • Short time survey method
  • Almost no material

4 Disadvantages

  • No single optimum way to survey
  • Some techniques are rapid and do not require repeat visits whereas other methods collect more individuals but can be resource intensive

5 Recommendations for methods application

  • Identify your sample station before coming to put the sampling material
  • Don’t pool together the data of stations or of the three techniques. Keep it separate for better accuracy in understanding and highlighting of habitat/species presence.

6 Cost

Mostly related to time effort.

  • 1-hour sampling/station * 4 stations = 4 hours sampling/site
  • Pitfall trap collection after 2 weeks. 20-30 minutes/station  2h/ site maximum
  • Material: garden trowel, tubes, laboratory pliers to collect invertebrates…
  • Identification of species in laboratory

7 Protocol and data analysis

  • Number of species with a high fidelity to riparian and floodplain habitats
  • Comparative analysis to highlight site’s importance.
  • Rarity
  • Other scoring metrics see (Pantheon)

One possibility is to analyse the invertebrate samples by using Pantheon (Heaver et al. 2017). By importing your species names, the software will provide information on its associated habitats (ISIS; Webb and Lott, 2006) and resources, habitat fidelity scores and other information thus giving numerical scores according to these characteristics and assist management decision. For more information contact on pantheon@ceh.ac.uk

8 References

  • Drake, C.M., Lott, D.A., Alexander K.N.A. and Webb J. (2007) Surveying terrestrial and freshwater invertebrates for conservation evaluation. Natural England Research Report NERR005. English Nature. Peterborough.
  • Sadler, J.P. & Bell, D. (2000) A comparative site assessment of exposed riverine (ERS) beetles in South-West England. English Nature Research Reports, No. 383, Peterborough.
  • Sadler, J.P. and Petts G.E. (2000) Invertebrates of Exposed Riverine Sediments – Phase 2: Sampling Considerations. Environment Agency: Bristol 112.
  • Webb, J. R., Drewitt, A. and Mott, N. (2017) Guidelines for Riparian Beetle Surveys incorporating site quality assessment via Pantheon. Natural England Protocol. Natural England