Monitoring and maintenance of kōura

Once you have identified the problem, and applied the necessary tools for restoring kōura to your stream, the next phase of your project is to monitor the site to see whether restoration works.

Monitoring your project is essential for discovering what worked, what didn’t, and what can be changed for future restoration. Many community-based projects are not monitored, and it is possible that while a stream might look better, its kōura population may not have improved. Ideally, a successful monitoring programme should involve before/after kōura surveys.

Kōura surveys should be conducted each year for 3-6 years. Ideally, a summer survey should be carried out each year for at least 3 years before restoration to establish a valid baseline, and then for 3 years post-restoration.

Where restoration is limited to riparian planting, which can take 5-10 years before any major changes are noticeable, post-restoration surveys are best left for at least 5 years. It may also be useful to make comparisons with streams similar to the one you restored.

Methods for carrying out kōura surveys depend on the habitat type. Consult a qualified and experienced freshwater ecologist to determine the best way to monitor your waterway.

Table 1: Summary assessment of stream kōura monitoring/sampling methods trialled in our study.

Method

Pros

Cons

Minnow traps

  • Widely used method
  • Suitable for range of habitats
  • Easy to relocate equipment
  • Moderate equipment costs
  • Suitable for a wide range of habitats
  • High variability between traps
  • No catch per unit area
  • Bias towards large male kōura
  • Use weather dependent
  • Theft potential
  • Return trip required
  • Low catches when eels present

Rama–spotlighting

  • Traditional fishing method
  • No specialist equipment
  • Quick method
  • Catch per unit area
  • Weather dependent
  • Limited to wadeable shallows
  • Visibility dependent
  • Biased towards large kōura
  • Biased towards shallow populations
  • Kōura abundance only. No size class data or breeding information
  • Sampling done at night
  • Low numbers observed when eels present

Electric fishing

  • Catch per unit area
  • Samples full size range
  • Good for sampling fish and other stream invertebrates
  • Specialist/costly equipment and training
  • Visibility dependent
  • High variability between samples
  • Suitable for shallow streams only
  • Not very effective in deep, soft-bottomed or weedy habitats
  • Use weather dependent
  • Potential harm to kōura and fish

Tau kōura -  individual bracken fern bundles

  • Traditional fishing method
  • Samples full size range
  • Large samples
  • Natural material
  • Suitable for range of habitats
  • Unobtrusive
  • Cheap
  • No clean-up required
  • Good for sampling benthic fish and other invertebrates
  • Catch per unit effort
  • No catch per unit area
  • Return trip required
  • Must be left for at least 2 weeks for kōura to colonise the fern
  • Prone to displacement by flooding
  • Fern needs to be available
  • Low catches when eels present

Fine mesh fyke nets

  • Widely used method
  • Suitable for range of habitats
  • Expensive equipment costs
  • Suitable for a wide range of habitats
  • Catch per unit effort
  • Potential vector for spread of pest plants and fish
  • High variability between nets
  • No catch per unit area
  • Use weather dependent
  • Theft potential
  • Return trip required
  • Not suitable for very small streams
  • Low catches when eels present
Research subject: EstuariesLakesRivers