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PURPOSE: To compare the three different population estimation methods To compare the three different population estimation methods Enumeration Mark/Recapture Depletion HYPOTHESES: Null (H 0 ): Enumeration = Mark/Recap = Depletion Null (H 0 ): Enumeration = Mark/Recap = Depletion Alternative (H A ): Enumeration Mark/Recap Depletion Alternative (H A ): Enumeration Mark/Recap Depletion

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P = sum of all individuals MINIMUM estimation MINIMUM estimation Assumptions All individuals are captured All individuals are captured Removal of individuals did not attract others Removal of individuals did not attract others into study area (vacuum effect) No births or deaths during the study No births or deaths during the study

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P = M x C R R M : # collected and marked during first sample M : # collected and marked during first sample C : # collected during second week sample C : # collected during second week sample R : # marked in the second sample R : # marked in the second sample Assumptions: All individuals are equally likely to be caught All individuals are equally likely to be caught Marked individuals are randomly dispersed Marked individuals are randomly dispersed Marked individuals must not become easier or more difficult to catch than unmarked individuals. Marked individuals must not become easier or more difficult to catch than unmarked individuals. No births, deaths, or migration No births, deaths, or migration

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Collect and remove (a constant fraction of the remaining population is taken with each sample) Apply a trendline and predict total population P = where the trendline crosses the x-axis Assumptions No births, deaths, or migration No births, deaths, or migration Probability of capture does not change Probability of capture does not change Probability of capture is the same for each individual Probability of capture is the same for each individual

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Collect and remove 8/20 5/12 3/7 = 0.40 = 0.41 = 0.42

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Depletion Graph X-axis: # snails collected so far Y-axis: #of snails collected in current sample * Where trendline crossed X-axis is your population estimate! Total # harvested today Total # harvested previous 100 9 819 727 734 641 547

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Small home range few square meters few square meters Pop sizes stable live for several years live for several years Easy to catch and mark Abundant unless Eco lab has been collecting them all week unless Eco lab has been collecting them all week

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200 collection minutes 5 groups of 4 10 min each 10 min each Volunteer group of 4 to go twice Volunteer group of 4 to go twice Process Collect snails Collect snails Dry snails Dry snails Mark all snails with paint pen (on bottom of the shell!) Mark all snails with paint pen (on bottom of the shell!) Bring all snails back to lab Bring all snails back to lab Last lab of the week will release ALL the snails collected all week.

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Measure: Air temp Air temp Water temp Water temp Water clarity (can you Water clarity (can you see the bottom?) see the bottom?) Depth Depth using meter stick at designated place Velocity Velocity meter stick and leaf in designated place

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Same as week 1 except: No marking snails No marking snails Keep track of: Keep track of: # marked (and what color) # unmarked 200 minutes of search time outside study area (to test for emigration): 200 minutes of search time outside study area (to test for emigration): 10 people search upstream for 10 minutes 10 people search downstream for 10 minutes Bring all snails from study plot back to lab (but only the marked migrants!) for Friday release!

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Measure (Again): Air temp Air temp Water temp Water temp Water clarity (can you Water clarity (can you see the bottom?) see the bottom?) Depth Depth using meter stick at designated place Velocity Velocity meter stick and leaf in designated place

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PURPOSE: To compare the three different population estimation methods To compare the three different population estimation methods Enumeration Mark/Recapture Depletion HYPOTHESES: Null (H 0 ): Enumeration = Mark/Recap = Depletion Null (H 0 ): Enumeration = Mark/Recap = Depletion Alternative (H A ): Enumeration Mark/Recap Depletion Alternative (H A ): Enumeration Mark/Recap Depletion

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Can be an indicator of: species health species health habitat quality habitat quality ecosystem or community health ecosystem or community health If done repeatedly over time, changes in population and its surroundings can be tracked especially threatened/endangered species especially threatened/endangered species Used in management decisions Hunting/fishing licenses Hunting/fishing licenses How areas are used in state/national parks How areas are used in state/national parks

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P = sum of all individuals MINIMUM estimation MINIMUM estimation Assumptions All individuals are captured All individuals are captured Removal of individuals did not attract others Removal of individuals did not attract others into study area (vacuum effect) No births or deaths during the study No births or deaths during the study

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P = M x C R R M : # collected and marked during first sample M : # collected and marked during first sample C : # collected during second week sample C : # collected during second week sample R : # marked in the second sample R : # marked in the second sample Assumptions: All individuals are equally likely to be caught All individuals are equally likely to be caught Marked individuals are randomly dispersed Marked individuals are randomly dispersed Marked individuals must not become easier or more difficult to catch than unmarked individuals. Marked individuals must not become easier or more difficult to catch than unmarked individuals. No births, deaths, or migration No births, deaths, or migration

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Collect and remove (a constant fraction of the remaining population is taken with each sample) Apply a trendline and predict total population P = where the trendline crosses the x-axis Assumptions No births, deaths, or migration No births, deaths, or migration Probability of capture does not change Probability of capture does not change Probability of capture is the same for each individual Probability of capture is the same for each individual

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Depletion Graph * Where trendline crossed X-axis is your population estimate! Total # harvested today Total # harvested previous 100 9 819 727 734 641 547