Growth, age at sexual maturity and condition in bearded seals (Erignathus barbatus) from Svalbard, Norway

Abstract

The aim of this study was to describe growth, determine age at sexual maturity and investigate the condition of bearded seals (Erignathus barbatus) collected in the fjords of Spitsbergen, Svalbard, Norway. Morphometric data, teeth and sex organs were collected from 110 animals. Age was determined by reading the cementum layers in hard longitudinal sections of canine teeth. Sexual maturity in males was determined according to the size of the testes and bacula. Females were defined as being sexually mature according to findings of mature follicles or corpora lutea/albicantia. Von Bertalanffy growth curves were applied to both standard length and body mass, and asymptotic values for males and females were 231.1 ± 11.4 cm and 269.9 ± 26.2 kg, and 233.1 ± 7.5 cm and 275.3 ± 47.8 kg, respectively. Maximum recorded lengths and masses were 254 cm and 313 kg in males and 242 cm and 358 kg in females. All males older than 6 years were found to have been sexually mature. Females were found to attain sexual maturity at about 90% of the asymptotic length, corresponding to an age of 5 years. In males a significant decrease in condition was observed from June to August, with a subsequent increase in September. In adult females, condition decreased from May to June and increased again from June to September. The conditional changes seen are likely to be due to the extra energetic cost and reduced food intake associated with reproduction, lactation and molt.