| Summary: | 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.
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