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Mark Recapture lecture 1

Mark Recapture lecture 1. An example from Sockeye salmon…. Mark recapture lectures. Petersen method Schnabel method Schumacher-Eschmeyer Jolly Seber. Closed population. Open population. Overview of methods to help your reading of Krebs Chp 2. Closed populations.

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Mark Recapture lecture 1

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  1. Mark Recapture lecture 1 An example from Sockeye salmon….

  2. Mark recapture lectures • Petersen method • Schnabel method • Schumacher-Eschmeyer • Jolly Seber Closed population Open population Overview of methods to help your reading of Krebs Chp 2

  3. Closed populations No individuals enter or leave the population between surveys Survey 2 Survey 1

  4. Open populations Individuals enter or leave the population between surveys Survey 2 Survey 1

  5. What makes a population closed? • Dispersal barriers • Philopatry • Large surveyed area • Slow reproductive/death rate • Short time between surveys

  6. What type of population are snow geese?

  7. Snow Goose La Pérouse Bay

  8. Recording which birds are marked, and marking new birds

  9. LPB Colony size Year

  10. Petersen method: Closed population Survey 1: Survey 2: Catch several animals Catch C animals Count recaptures (R) Mark all M animals Return animals to population Return animals to population

  11. Survey 2: Survey 1: M = 12 C = 15 R = 4

  12. M = R N C N = M C R What is the total population size (N)? Note that the proportion marked in the population equals the proportion marked in the 2nd sample M = 12 C = 15 R = 4

  13. N = 13 * 16 5 -1 What is the total population size (N)? Note that the proportion marked in the population equals the proportion marked in the 2nd sample N = (M+1) (C+1) (R+1) -1 M = 12 C = 15 R = 4

  14. When would Petersen give you a bad estimate? • Population not closed • Marked animals likely to be re-trapped • Marked animals likely to die • Marks fall off

  15. Survey 2 Survey 3 Survey 4 Survey 5 Schnabel method: closed population Survey 1 Essentially, Petersen estimates on multiple surveys

  16. Survey t: Catch Ct animals Record Rt recaptures Mark Ut unmarked animals Return animals to population Schnabel method: closed population

  17. Schnabel method: closed population Survey t: Catch Ct animals What’s the relationship between Ct, Rt, and Ut ? Record Rt recaptures Mark Ut unmarked animals Ct = Rt + Ut Return animals to population

  18. Schnabel method: example How many individuals marked by beginning of time 5?

  19. Schnabel method: example How many individuals marked by beginning of time 5?

  20. Schnabel method: example Σ = 58

  21. Schnabel method: example In general: Mt = U1 + U2..Ut-1 Σ = 58

  22. Schnabel formulas: Marked > 10% of population N = Σ (Ct Mt) Σ Rt N = Σ (Ct Mt) Σ Rt+1 Marked < 10% of population ( just weighted average of Petersen estimates!)

  23. Schnabel method: example 0 48

  24. Schnabel method: example 0 48 Σ = 2060 Σ = 22

  25. Schnabel method: example N = Σ (Ct Mt) = 2060 = 94 Σ Rt 22 0 48 Σ = 2060 Σ = 22

  26. Schnabel method: example What proportion of total population marked by end? 0 48 Σ = 2060 Σ = 22

  27. R = 1 * M C N Scumacher-Eschmeyer method (for Schnabel experiment) N = C M R y = mx + b

  28. R = 1 * M C N Scumacher-Eschmeyer method (for Schnabel experiment) N = C M R R C Slope = ? M

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