Abstract
This study is aimed at establishing the mean age at attainment of sexual maturity and birth rates of harbour seals at the Norwegian coast, using information from 172 female and 184 male harbour seals sampled between 62 and 66° N during the period 1977–1982. Based on the occurrence of first time ovulation, the mean age at attainment of female sexual maturity was 3.75 years. The mass of ovaries showed maximum rate of increase between three and five years of age. Testicular growth indicates that males matured between five and seven years of age. The birth rate increased from 0.2 in four-year-old females to 0.5 in six-year-olds and to 0.9 in females eight years of age and older.
