During 1988, 1989 and 1995, 187 harbour porpoises (Phocoena phocoena) were sampled from the catches off West Greenland during the months of July, August and September. The samples were taken between 62°N and 69°30′N in Maniitsoq and three more northerly locations (134), Paamiut (23), and Nuuk (30). Comparison of age and length distributions between years and areas, indicated that there were no significant differences between years. However, the Maniitsoq and northerly samples had a modal age in both sexes of about 2 yr and a maximum age of 17 yr, while the more southerly Nuuk and Paamiut samples were biased to younger age classes, with the modal age in both sexes being the first year of life (age class 0 yr) and a maximum age of 12 yr.
Females ovulated from age 3.6 yr at a length of about 142 cm; combined testes weights > 200 g indicated maturation in males from age 2.5 yr upwards at a length > 125 cm. Several small embryos were found, consistent with a mating season in late summer. Testis hypertrophy in August was also consistent with a late summer breeding. Application of growth models indicated an average asymptotic length of 154 cm in females and 143 cm in males.
Comparisons of the West Greenland data with similar data for porpoises from the Canadian Atlantic, eastern North Atlantic and the North Sea, where genetic studies have shown population differences, indicated differences in biological parameters.