Sampling techniques

• Systematic sampling


  Line transect:

  organisms touching the string are recorded

  Belt transect:

  quadrats placed along transect. Continuous/interrupted
• Pond net


  method:

  swept through water to capture invertebrates.

  Standardise the number and length of sweeps.

  
  

  limitation:

  mobile species may escape

  accurate standardisation is difficult
• Kick sampling


  method:

  net held on riverbed facing open current. The riverbed is disturbed by scraping a boot over it.

  Standardise the number and length of kicks.

  
  

  limitation:

  organisms fixed in stone aren't dislodged

  some may swim and avoid line
• Pitfall traps


  method:

  container placed in hole with its open end up, level to surface. Cover is supported over opening to exclude predators and prevent flooding. Trap checked every 24 hrs.

  limitations:

  only mobile species caught

  preservatives used may attract/repel species
• earthworm extraction: soil flooding


  method:

  1. mark out a suitable sample area.
  2. remove surface vegetation.
  3. add irritant solution (detergent, mustard water) until saturated. Also saturate the surrounding area.
  4. collect worms that surface until no more appear/ standardised time period.
  5. count/ measure/ weigh/ identify.

  Limitations:

  irritant may not percolate through impermeable soils.

  irritant may not reach deep worms.

  worms may move down/ sideways.