ABSTRACT
Information about the age of fish is used to determine rates of mortality, growth, and maturation, which are key components of population models used to make fisheries management decisions. Ages of fish are often estimated by assessing patterns found in calcified structures such as scales, fin rays or spines, and otoliths. Bias among structures or technicians is determined from paired age estimates for the same fish. The shad data examines accuracy by comparing the estimated ages from a biologist to the known ages, bias between biologists by comparing the age estimates for two biologists and precision by comparing between the two estimates by the same biologist and also by comparing among the first estimates of all three biologists. In an age bias plot, the mean age and associated confidence interval computed from the nonreference ages for each reference age is plotted against the corresponding reference age.
