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Recommendations for estimating mark rate of cetaceans in photo‐ID research: A critique of field sampling protocols and variance estimation
Author(s) -
Wickman Lindsay,
Rayment William,
Slooten Elisabeth,
Dawson Stephen M.
Publication year - 2021
Publication title -
marine mammal science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.723
H-Index - 78
eISSN - 1748-7692
pISSN - 0824-0469
DOI - 10.1111/mms.12723
Subject(s) - statistics , estimator , bayes' theorem , variance (accounting) , frequentist inference , sampling (signal processing) , population , bayesian probability , bayes estimator , sample size determination , mathematics , econometrics , computer science , bayesian inference , demography , accounting , filter (signal processing) , sociology , business , computer vision
Mark rate, or the proportion of the population with unique, identifiable marks, must be determined in order to estimate population size from photographic identification data. In this study we address field sampling protocols and estimation methods for robust estimation of mark rate and its uncertainty in cetacean populations. We present two alternatives for estimating the variance of mark rate: (1) a variance estimator for clusters of unequal sizes (SRCS) and (2) a hierarchical Bayesian model (SRCS‐Bayes), and compare them to the simple random sampling (SRS) variance estimator. We tested these variance estimators using a simulation to see how they perform at varying mark rates, number of groups sampled, photos per group, and mean group sizes. The hierarchical Bayesian model outperformed the frequentist variance estimators, with the true mark rate of the population held in its 95% HDI 91.9% of the time (compared with coverage of 79% for the SRS method and 76.3% for the SRCS‐Cochran method). The simulation results suggest that, ideally, mark rate and its precision should be quantified using hierarchical Bayesian modeling, and researchers should attempt to sample as many unique groups as possible to improve accuracy and precision.