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Complete and Sampled Counts

  • Summary of Random Sampling types:

    Sample

    Use

    Advantages

    Disadvantages

    SRS

    small geographic area w/ not much variation, not many sample units

    simple formulas

    long travel time

    Stratified RS

    distribution depends clearly on well defined attributes

    more efficient estimates

    its okay

    systematic sampling

    anywhere, as long as first unit is randomly placed

    best type, most efficient

    problems with small samples

  • Mark-recapture
    • mark resight: used for large animals or other animals that are not good to recapture
  • Distance Sampling: plot and line samples; incomplete counts are corrected by visibility bias. Stand and look. Doesn't sound legit.
  • Indicies: instead of counting the number of animals, count their "effects" (footprints, etc).
  • Field methods for fish:
    • Pilot studies should be done first
    • Sampling should extensive, not intensively based
    • Fish distribution is different than for other animals--they are clumped tightly (they Hilborne and Walters, 1992)