Post on 23-Feb-2016
description
Ecology Lab Week 1 Population Estimation
Ecology Lab Population Estimation (Week 1)
1Population EstimationPURPOSE: To compare the three different population estimation methodsEnumerationMark/RecaptureDepletion
HYPOTHESES: Null (H0): Enumeration = Mark/Recap = DepletionAlternative (HA): Enumeration Mark/Recap Depletion 2Method 1: EnumerationP = sum of all individualsMINIMUM estimation
AssumptionsAll individuals are capturedRemoval of individuals did not attract others into study area (vacuum effect)No births or deaths during the study3Method 2: Mark/Recapture P = M x C R
M : # collected and marked during first sampleC : # collected during second week sampleR : # marked in the second sample
Assumptions:All individuals are equally likely to be caughtMarked individuals are randomly dispersedMarked individuals must not become easier or more difficult to catch than unmarked individuals.No births, deaths, or migration
4Method 3: DepletionCollect and remove Collect and removeCollect 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
AssumptionsNo births, deaths, or migrationProbability of capture does not changeProbability of capture is the same for each individual5Method 3: DepletionCollect and remove
Collect and remove
Collect and remove8/205/123/7= 0.40= 0.41= 0.426Depletion GraphX-axis: # snails collected so farY-axis: #of snails collected in current sample
* Where trendline crossed X-axis is your population estimate!Total # harvested todayTotal # harvested previous1009108197277346415477Why are we using snails?Yellow elimia (Elimia flava)
Small home rangefew square meters
Pop sizes stablelive for several years
Easy to catch and mark
Abundant unless Eco lab has been collecting them all week
8Snail Sampling Method200 collection minutes5 groups of 4 10 min eachVolunteer group of 4 to go twice
ProcessCollect snailsDry snailsMark all snails with paint pen (on bottom of the shell!)Bring all snails back to lab
Last lab of the week will release ALL the snails collected all week.
9Creek CharacteristicsMeasure:
Air temp
Water temp
Water clarity (can you see the bottom?)
Depth using meter stick at designated place
Velocitymeter stick and leaf in designated place
10Same as week 1 except: No marking snails
Keep track of:# marked (and what color)# unmarked
200 minutes of search time outside study area (to test for emigration):10 people search upstream for 10 minutes10 people search downstream for 10 minutes
Bring all snails from study plot back to lab (but only the marked migrants!) for Friday release!Week Two MethodsCreek CharacteristicsMeasure (Again):
Air temp
Water temp
Water clarity (can you see the bottom?)
Depth using meter stick at designated place
Velocitymeter stick and leaf in designated place
13Ecology Lab Population Estimation (Week 3)14PURPOSE: To compare the three different population estimation methodsEnumerationMark/RecaptureDepletion
HYPOTHESES: Null (H0): Enumeration = Mark/Recap = DepletionAlternative (HA): Enumeration Mark/Recap Depletion Review: Population Estimation15Can be an indicator of:species healthhabitat qualityecosystem or community health
If done repeatedly over time, changes in population and its surroundings can be trackedespecially threatened/endangered species
Used in management decisionsHunting/fishing licensesHow areas are used in state/national parksWhy estimate population size?How is this tool valuble?Method 1: EnumerationP = sum of all individualsMINIMUM estimation
AssumptionsAll individuals are capturedRemoval of individuals did not attract others into study area (vacuum effect)No births or deaths during the study17Method 2: Mark/Recapture P = M x C R
M : # collected and marked during first sampleC : # collected during second week sampleR : # marked in the second sample
Assumptions:All individuals are equally likely to be caughtMarked individuals are randomly dispersedMarked individuals must not become easier or more difficult to catch than unmarked individuals.No births, deaths, or migration
18Method 3: DepletionCollect and remove Collect and removeCollect 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
AssumptionsNo births, deaths, or migrationProbability of capture does not changeProbability of capture is the same for each individual19Depletion Graph* Where trendline crossed X-axis is your population estimate!Total # harvested todayTotal # harvested previous10091081972773464154720