Last modified on Mar 05, 2019

Buckmeier (2002) found that many readers produced biased estimates. Any set of age estimates contain error (Beamish and McFarlane, 1983), and if the error is random, the true age distributions of the population can be estimated. Lai et al. (1996) found that biased errors altered estimates of mortality, growth, and production. Campana (2001) noted that quality control could be used to monitor bias and ensure that estimations remained consistent. Known-age reference structures allow readers to verify their age estimates are accurate and unbiased. Acceptable levels of accuracy and bias need to be established, and readers should be periodically tested. Readers failing to meet standards would be re-trained prior to independently estimating age. Often, known age fish are unavailable, and when this occurs, readers cannot verify that they are accurately estimating fish age. Buckmeier (2002) found that the use of multiple readers reduced error and bias in most instances, although there was still a tendency to underestimate the age of older fish. (#SK results here?).


Beamish, R.J., McFarlane, G.A., 1983. The forgotten requirement for age validation in fisheries biology. Transactions of the American Fisheries Society 112 (6), 735-743.

Buckmeier, D.L., 2002. Assessment of reader accuracy and recommendations to reduce subjectivity in age estimation. Fisheries 27 (11), 10-14.

Campana, S., 2001. Accuracy, precision and quality control in age determination, including a review of the use and abuse of age validation methods. Journal of Fish Biology 59 (2), 197-242.

Lai, H.-L., Gallucci, V.F., Gunderson, D.R., Donnelly, R.F., 1996. Age determination in fisheries: methods and applications to stock assessment. In: Gallucci, V.F., Saila, S.B., Gustafson, D.J., Rothschild, B.J. (Eds.), Stock assessment: quantitative methods and applications for small-scale fisheries. CRC Press, New York, pp. 82-178.