Adjusting for Recapture Uncertainty: Improved Abundance Estimates from Capture-Recapture Surveys

• Activity Number: 233
• Type: Topic Contributed
• Date/Time: Monday, August 5, 2013 : 2:00 PM to 3:50 PM
• Sponsor: Section on Statistics and the Environment
• Author(s): Stacy Edmondson*+
• Companies: Colorado State University
• Keywords: mark-recapture ; sight-resight ; independent observer ; abundance estimation ; MCMC

Abstract

A problem for capture-recapture survey analysis arises when the recaptures or re-identifications are uncertain. This occurred in ice-based visual surveys of the Bering-Chukchi-Beafort Seas (BCBS) stock of bowhead whales, (Balaena mysticetus) near Barrow, Alaska. A two-perch independent observer protocol provided data amenable for analysis with classical capture-recapture statistical methods for estimating population abundance and detection probabilities, such as the Huggins (1989) model, except for the recapture problem. Due to the behavior of large marine mammals, environmental conditions and the design of the study, physically marking the whales is impossible. Instead, recaptures are identified post hoc using integrative subjective judgments and are subject to error. I introduce a model that incorporates sighting and recapture error rates into the Huggins (1989) framework and a Bayesian estimation strategy using MCMC over a vast combinatorial parameter space. Simulation results illustrate the method's performance and further challenges.