@article{Ólafsdóttir_Víkingsson_Halldórsson_Sigurjónsson_2003, title={Growth and reproduction in harbour porpoises (<i>Phocoena phocoena</i>) in Icelandic waters}, volume={5}, url={https://septentrio.uit.no/index.php/NAMMCOSP/article/view/2747}, DOI={10.7557/3.2747}, abstractNote={&lt;div&gt;A total of 1,268 harbour porpoises were obtained from fishing nets in Icelandic coastal waters from September to June in the years 1991 to 1997. Foetal sex ratio was 1.2:1 (male:female). The&amp;nbsp;&lt;span style=&quot;font-size: 10px;&quot;&gt;bias towards males increased further among older animals in the present collection. The modal&amp;nbsp;&lt;/span&gt;&lt;span style=&quot;font-size: 10px;&quot;&gt;year classes were 0 and 1 years but the oldest porpoise was a female estimated at 20 years of age.&amp;nbsp;&lt;/span&gt;&lt;span style=&quot;font-size: 10px;&quot;&gt;Length at birth was estimated as approximately 75 cm, and females grew faster and attained larger&amp;nbsp;&lt;/span&gt;&lt;span style=&quot;font-size: 10px;&quot;&gt;sizes than males. Asymptotic length was 149.6 cm for males and 160.1 cm for females. Estimated&amp;nbsp;&lt;/span&gt;&lt;span style=&quot;font-size: 10px;&quot;&gt;age and length at sexual maturity was 1.9 to 2.9 years and 135 cm for males and 2.1 to 4.4 years&amp;nbsp;&lt;/span&gt;&lt;span style=&quot;font-size: 10px;&quot;&gt;and 138 to 147 cm for females. Immature individuals were significantly shorter than pubertal and&amp;nbsp;&lt;/span&gt;&lt;span style=&quot;font-size: 10px;&quot;&gt;mature animals in both sexes in age classes 1 to 3. Testes weight increased only slightly with body&amp;nbsp;&lt;/span&gt;&lt;span style=&quot;font-size: 10px;&quot;&gt;size in immature males but increased rapidly around maturity. Pronounced seasonality was also&lt;/span&gt;&lt;/div&gt;&lt;div&gt;observed in testes weight, indicating a peak in testes activity in summer. Lack of data from the&amp;nbsp;&lt;span style=&quot;font-size: 10px;&quot;&gt;summer makes the exact timing of parturition and mating unknown. Births do, however, most&amp;nbsp;&lt;/span&gt;&lt;span style=&quot;font-size: 10px;&quot;&gt;likely peak in June and July and lactation lasts at least 7 to 8 months. Ovulation and pregnancy&amp;nbsp;&lt;/span&gt;&lt;span style=&quot;font-size: 10px;&quot;&gt;rates were 0.98.&lt;/span&gt;&lt;/div&gt;}, journal={NAMMCO Scientific Publications}, author={Ólafsdóttir, Droplaug and Víkingsson, Gísli A and Halldórsson, Sverrir Daníel and Sigurjónsson, Jóhann}, year={2003}, month={Jul.}, pages={195–210} }