Age determination and the growth and age distribution from cementum growth layers of bearded seals at Svalbard

Abstract

BENJAMINSEN, T. 1973. Age determination and the growth and age distribution from cementum growth layers of bearded seals at Svalbard. FiskDir. Skr. Ser. HavUnders., 16:159-170. Material for this study was collected from 177 bearded seals on a sealer at Svalbard in 1968 and from 18 seals studied by biologists at Svalbard and in the Barents Sea in 1968 and 1970. Bearded seal teeth degenerate and are lost at an early age, but canines in the upper jaw remain, apparently throughout life. They wear down at a linear rate. Dentine cannot be used for age determination, but cementum growth layers are added annually and permit age determinations also of adult seals. Growth layers in claws wear off after about 10 years. Bearded seals grow to a mean adult length of 225 cm at about 10 years. Females are slightly, but not significantly, larger than males. At Svalbard age-groups are fully recruited at 9 years and live to an age of about 31 years. A total annual mortality of 0.14 has provisionally been estimated for adult bearded seals at Svalbard.