@article{Lockyer_2003, title={Harbour porpoises (<i>Phocoena phocoena</i>) in the North Atlantic: Biological parameters}, volume={5}, url={https://septentrio.uit.no/index.php/NAMMCOSP/article/view/2740}, DOI={10.7557/3.2740}, abstractNote={&lt;div&gt;Biological parameters for harbour porpoises are reviewed throughout their range in the North&amp;nbsp;&lt;span style=&quot;font-size: 10px;&quot;&gt;Atlantic. Most information is based on studies of a combination of directed catches, bycatches&amp;nbsp;&lt;/span&gt;&lt;span style=&quot;font-size: 10px;&quot;&gt;and strandings. All these sources are valuable for providing biological information, but each carries&amp;nbsp;&lt;/span&gt;&lt;span style=&quot;font-size: 10px;&quot;&gt;some bias when it comes to interpretation of parameters, especially those involving age structure.&amp;nbsp;&lt;/span&gt;&lt;/div&gt;&lt;div&gt;&lt;br /&gt;&lt;/div&gt;&lt;div&gt;&lt;span style=&quot;font-size: 10px;&quot;&gt;Information on age-related parameters, reproduction and growth is presented and assessed by&amp;nbsp;&lt;/span&gt;&lt;span style=&quot;font-size: 10px;&quot;&gt;region and/or population, of which there may be 14 throughout the North Atlantic. Among age related&amp;nbsp;&lt;/span&gt;parameters, maximum longevity recorded is 24 years; maximal rate of population growth is probably 9.4% but in the range 5-10%; mortality is highest in year 1, and &amp;lt;5% of the population&amp;nbsp;live beyond 12 years; an estimate of 0.867 with a maximum age of 23 years has been given&amp;nbsp;for survival. Among reproductive parameters, age at sexual maturation falls between 3-4 years&amp;nbsp;for both sexes; age at first parturition is probably 4-5 years; age at first ovulation is &amp;gt;3 years; ovulation&amp;nbsp;rates fall in the range 0.64 - 0.988 corpus per year, and reproductive interval is 1.01-1.57&amp;nbsp;years; pregnancy rates are generally in the range 0.74 - 0.986 per year, meaning that not all females&amp;nbsp;produce a calf every year; there is seasonal breeding/mating in the period June&amp;ndash;August; gestation&amp;nbsp;lasts 10-11 months; parturition generally occurs between mid-May to mid-July; duration of&amp;nbsp;lactation is uncertain, but is probably at least 8 months; size at birth is usually in the range 65-75 cm with a maximum size of about 80 cm. Sex ratio is biased to males throughout life: 1.1-1.2&amp;nbsp;males : 1.0 females in the foetal stage, and 1.1-1.7 males : 1.0 females post-natal. Growth parameters&amp;nbsp;indicate an asymptotic length and weight that varies with population, but usually falls in&amp;nbsp;the range 153-163 cm and 55-65 kg for females and 141-149 cm and 46-51 kg for males. Growth&amp;nbsp;models used for length and weight are typically based on von Bertalanffy and Gompertz models.&amp;nbsp;Length at sexual maturity also varies with population, but is usually in the range&amp;nbsp;138-147 cm for females and 127-135 cm for males. There is no information based on vertebral&amp;nbsp;epiphyseal fusion to indicate age at physical maturity. Foetal growth appears normal, but there is&amp;nbsp;uncertainty about the existence of embryonic diapause. Size/age at weaning are uncertain, but size&amp;nbsp;may be &amp;lt;115 cm and at an age &amp;gt;8 months; however, entirely independent feeding may not occur&amp;nbsp;until about 10 months.&lt;span style=&quot;white-space: pre;&quot;&gt; &lt;/span&gt;&lt;/div&gt;}, journal={NAMMCO Scientific Publications}, author={Lockyer, Christina}, year={2003}, month={Jul.}, pages={71–89} }