A critical evaluation of age determination of ringed seals (Phoca hispida Schreber 1775) /

• Main Author: Albright, Don
• Format: Thesis
• Language: English
• Published: McGill University 1990
• Subjects: Ringed seal > Age determination; Phoca hispida; ringed seal
• Online Access: http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=59818

Precision of determining age in ringed seals (Phoca hispida) was examined by repeated readings of undecalcified cross sections and decalcified stained longitudinal sections of mandibular canines. There appeared to be geographical differences in repeatability although this could not be tested statistically. There was no difference in repeatability between cross and stained sections. The effect of precision on population parameters was examined. Smoothing procedures necessary to construct life tables and to do Leslie matrix calculations obscured any differences in ages between readings. Variance between readings was found to give inconsistent notions of sexual maturity. Imprecision caused little overall difference in growth curves. Without known age animals, accuracy cannot be evaluated directly. High correlation between ages from canines from different sides of the same animal, between dentine and cementum of teeth from the same animal, and between readers examining the same sets of teeth gave an indirect suggestion of accuracy.