Growth rate and intra-seasonal changes in body condition of harbour porpoises (Phocoena phocoena)

• Main Authors: Stepien, Emilie Nicoline, Tange Olsen, Morten, Hansen, Kirstin Anderson, Højer-Kristensen, Jakob, Blanchet, Marie-Anne, Brando, Sabrina, Desportes, Geneviéve, Lockyer, Christina, Marcenaro , Lauro, Siebert, Ursula, Wahlberg, Magnus
• Format: Conference Object
• Language: English
• Published: 2018
• Subjects: body condition score; growth; harbour porpoise; Harbour porpoise; Phocoena phocoena
• Online Access: https://pure.au.dk/portal/da/publications/growth-rate-and-intraseasonal-changes-in-body-condition-of-harbour-porpoises-phocoena-phocoena(290f78dc-a924-411a-a009-ba94341a9f31).html

In cetaceans, growth curves and season-dependent morphometric measurements are usually obtained from stranded or bycaught individuals and little longitudinal data is available. This may bias data on age- and sex-related growth as well as the health status of the animals. This study investigates long-term growth rate and seasonal variations in body size of individual harbour porpoises (Phocoena phocoena) under human care. This unique, long-term longitudinal data includes regular measurements of girth, blubber thickness, length, and weight for up to 14 years of five harbour porpoises kept in a semi-open facility. In addition, growth rate of five captive-born calves were calculated from birth. Our results show that growth rate is extremely rapid during the first year of life, slows down until age 3-5 years, and reaches a plateau after 6 years of age. Although growth seems to slow down or even stop in individuals older than 6 years, large seasonal variations in body weight, body girth and blubber thickness are evident. Our study demonstrates that it is possible to obtain individual age and body condition using a few measurements of length and girth. This allows for the possibility of non-invasive estimates of age and body condition in the field e.g. using photogrammetry.