Estimation and effects of tag-misread rates in capture-recapture studies

Virtually all capture-recapture studies assume that tags are read properly when an animal is captured. However, the animals in resighting studies are often not handled, tags are read at a distance, and misreads can occur. In this paper, we develop a simple model to account for misreads, assess the i mpact of misreads upon estimates of survival and catchability, and analyze a set of data from resightings of previously branded seals. In general, unl ess survival, capture, and misread rates are relatively high, most studies have poor power to detect misreads and estimates of survival are not severe ly biased. Estimates of capture rates will be biased downwards and will ten d to estimate the product of the original capture rate and the complement o f the misread rate.