Life history of harbor porpoises (Phocoena phocoena) in Scottish (UK) waters

Abstract

Life history parameters were determined for stranded and bycaught\nharbor porpoises (Phocoena phocoena) from Scottish (UK) waters (1992â 2005).\nFetal growth rate was 84.4 mm/mo and mean size at birth was 76.4\ncm (range 65â 88 cm). Males and females had a similar range of body\nlengths (65â 170 cm and 66â 173 cm, respectively), although asymptotic\nlengths were higher in females than males (approximately 158 cm and\n147 cm, respectively). Nonpregnant females were significantly lighter,\nin relation to their length than males. Maximum estimated age was\n20 yr for both sexes. Age at sexual maturity (ASM) was estimated\nas 4.35 yr in females and 5.00 yr in males. Conception occurred mainly\nin July and August although reproductively active males were recorded\nduring April to July. Gestation lasted 10â 11 mo, with calving mainly\nbetween May and July. Lactating females were recorded during June\nto November, while small calves with solid food in their stomachs\nwere found mainly during February to May. Estimated pregnancy rate\n(0.34â 0.40) is lower than recorded elsewhere, but is likely underestimated\ndue to the prevalence of mature females of poor health status in\nthe sample. Nevertheless, cetacean strandings can be an essential\nsource of data on demographic parameters.