Age at Sexual Maturity and Pregnancy Rates of Harbour Porpoises Phocoena phocoena from the Bay of Fundy

• Published in: Canadian Journal of Fisheries and Aquatic Sciences
• Main Author: Read, Andrew J.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1990
• Subjects: Phocoena phocoena
• Online Access: http://dx.doi.org/10.1139/f90-064; http://www.nrcresearchpress.com/doi/pdf/10.1139/f90-064

Age at sexual maturity and pregnancy rate were estimated from a sample of 108 female harbour porpoises Phocoena phocoena killed incidentally in a commercial gill net fishery in the Bay of Fundy during July–September, 1985–88. Estimates of sexual maturity ranged from 3.15 to 3.44 yr, depending on the method used; few individuals older than 7 yr of age were present in the sample. The mean age at first pregnancy was 3.76 yr. Pregnancy rate was estimated using two methods: (1) considering the entire sample and using the presence of a corpus luteum as indicative of pregnancy, and (2) by considering the sample collected after implantation and using the presence of a foetus as the criterion of pregnancy. Estimated pregnancy rates using these two methods were 0.86 and 0.74, respectively. Many young females failed to conceive in their first year or two of sexual maturity, but most older females in the sample were pregnant. These high pregnancy rates are indicative of annual reproduction in this population.