PURPOSE: To compare the three different population estimation methods To compare the three different population estimation methods Enumeration Mark/Recapture.
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Slide 1
Slide 2
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
Slide 3
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
Slide 4
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
Slide 5
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
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
Slide 8
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
Slide 9
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.
Slide 10
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
Slide 11
Slide 12
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!
Slide 13
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
Slide 14
Slide 15
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
Slide 16
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
Slide 17
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
Slide 18
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
Slide 19
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
Slide 20
Depletion Graph * Where trendline crossed X-axis is your
population estimate! Total # harvested today Total # harvested
previous 100 9 819 727 734 641 547