Statistics Senior Thesis Defense by Sophie Lu '19, Wednesday, May 1
Wed, May 1st, 2019
1:10 pm - 1:50 pm
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Bayesian Estimation of Age at First Capture in Mark-Recapture Studies of Trinidadian Guppies, by Sophie Lu ’19, Wednesday, May 1, 1:10 – 1:50 pm, Stetson Court Classroom 105, Statistics Senior Thesis Defense
Abstract: The age of an organism is a strong predictor of organismal fitness. However, in ecological studies, age cannot be measured directly for many wild populations. Furthermore, age correlates reasonably well with other organismal traits that researchers can directly measure. The estimation of these traits over successive time periods allows the estimation of age via these other variables.
The Guppy Project has been conducting a longitudinal study on populations of Trinidadian guppies, the model organism system used to study ecological and evolutionary processes for over a decade. In order to understand population attributes such as aging and growth in the wild, it is important to be able to identify the age of an organism. Since the guppies are small and born live, they cannot be marked until they reach a specific length. Thus, the age of these organisms are unknown at recapture during the monthly mark-recapture procedures.
We constructed a hierarchical model using a Bayesian framework to estimate the age of a given fish in a population. Using early-life data and mark-recapture census data from two series of data over consecutive three-months each, we generated inferences for the birth dates for each fish, which gives the estimates for age for each fish. By this model structure, we may input the sizes of guppies, measured by standard length, and extract reliable age estimates. Our hierarchical model structure uses latent categorical indicators to model the imperfect identification of specific individuals in size cohorts in the mark-recapture study, until the individuals are large enough to receive uniquely identifiable marks. This approach is novel to methodology in mark-recapture studies.
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