FANR 3000 1st Edition Lecture 13 Outline of Last Lecture I Imperfect detection II Binomial distribution III Abundance IV Detectability V Distance Sampling Outline of Current Lecture I Capture Mark Recapture II CMR Assumptions III Abundance Estimation Current Lecture I Capture Mark Recapture CMR Most popular way to measure the size of a population Used by fish and wildlife managers to estimate population sizes before fishing hunting seasons Uses the Lincoln Petersen model to calculate population estimate 1 A sample of the population is captured 2 Individuals are marked and then returned to the population 3 Population is re sampled o Based on the idea that the proportion of marked animals in the 2nd sample should be the same as the proportion of marked animals of the entire population R C M N RN MC N MC R R number of animals captured on the 1st visit that were then recaptured on the 2nd visit These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute II III C total numbers of animals captured on the 2nd visit regardless of mark M total number of animals captured and marked on the 1st visit N estimate of the total population size o However it is biased for small capture samples Fixe bias using bias adjusted estimate N M 1 C 1 R 1 1 CMR Assumptions The accuracy of this capture mark recapture methods rests on a number of assumptions being met 1 The population is closed N is constant a The two visits to the study are are close enough in time so that no individuals dies are born move into the study area or move out of the study area between visits 2 All individuals have the same chance of getting caught for both capturing periods a Marked individuals must not become easier or more difficult to catch 3 Marking individuals does not affect their ability to be caught a The mark may make the individual more noticeable to predators or may slow them down so more marked individuals die than unmarked between the sampling periods 4 Individuals do not lose their marks a Animals that shed or molt as they grow or as a response to seasonal factors Abundance Estimation Estimating the total number in a population N o It s usually impossible to get a census of a natural population of animals o We rely on an estimate A variety of estimation methods exist Depends on the type of organism habitat time and equipment