Sampling

• Sampling is more time efficient, and is more likely to be accurate due to miscounting
• Sampling uses random areas to remove bias
• Sampling uses large numbers of samples generally over 30
• Non-Motile Sampling = Quadrat

  • Uniform = random sampling
  • Uneven Distribution = line transect
• Motile Sampling = Mark-Release-Recapture
• Random Sampling Method:

  • 2 tapes at right angles to eachother creating co-ords
  • Random number generator
  • Place quadrat, collect data (density, % cover, frequency)
  • Repeat 30+ times, calculate a mean
• Line Transect Method:

  1. Belt = quadrat at every position
  2. Interrupted Belt = quadrat at intervals

  • Right angle to shoreline
  • Place quadrat at every 5m
  • Collect data (density, % cover, frequency)
  • Repeat 30+ times, moving transect down the beach
• Mark-Release-Recapture Method:

  • Initial sample caught, marked, and released in same place to randomly disperse for set period
  • 2nd sample caught, count how many total and how many marked
  • Use estimated population formula
• Estimated Total Population Formula

  1st caught x 2nd caught / number of marked recaptured
• Ethical Implications:

  • Use non-toxic marks
  • Must not increase predatation
  • Must not reduce reproduction
• Assumptions in Sampling:

  • Population size remains constant (no birth/death, migration)
  • Sample redistributes evenly