ORIGINAL PAPER M. Andersen á A.M. Hjelset á I. Gjertz C. Lydersen á B. Gulliksen Growth, age at sexual maturity and condition in bearded seals (Erignathus barbatus) from Svalbard, Norway Accepted: 28 July 1998 Abstract The aim of this study was to describe growth, determine age at sexual maturity and investigate the condition of bearded seals (Erignathus barbatus) col- lected 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 ac- cording to the size of the testes and bacula. Females were de®ned as being sexually mature according to ®ndings of mature follicles or corpora lutea/albicantia. Von Bertalany 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 asymp- totic length, corresponding to an age of 5 years. In males a signi®cant decrease in condition was observed from June to August, with a subsequent increase in Septem- ber. 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. Introduction The bearded seal (Erignathus barbatus) is a large phocid seal, with a circumpolar and boreoarctic distribution (King 1964), which has received less attention from scientists than most other arctic seal species. Aspects of its biology have, however, been described from several parts of the Arctic region. Growth, reproduction, pop- ulation structure and feeding of bearded seals have been studied in several dierent geographical areas (Chapskii 1938; McLaren 1958; Benjaminsen 1973; Fedoseev 1973; Potelov 1975; Lowry et al. 1980; Smith 1981; Burns and Frost 1983; Antonelis et al. 1994; Hjelset et al., in press). Recently, studies of diving, energetics, migrations and pup development have been conducted on bearded seals breeding in the fjords of western Spitsbergen, Svalbard, Norway (Hammill et al. 1994; Lydersen et al. 1994, 1996; Gjertz et al. 1995; Kovacs et al. 1996). Since un- derstanding the ecology of a species is highly important for its management, vital aspects of its biology must be studied. To be able to follow trends in population structure through time and to evaluate the eects of interactions with other species or human exploitation of renewable and nonrenewable resources, information on growth patterns, reproductive characteristics and body condition is needed. Benjaminsen (1973) investigated the growth and age distribution of a large sample of bearded seals from the Svalbard area and the Barents Sea. This is the only in- vestigation covering Svalbard waters; however, most of Benjaminsen's sample was collected in the open ocean east of Spitsbergen. In the present study we examined bearded seals col- lected from the fjords of western Spitsbergen, Svalbard, Polar Biol (1999) 21: 179±185 Ó Springer-Verlag 1999 M. Andersen á A.M. Hjelset á B. Gulliksen Norwegian College of Fishery Science, University of Tromsù, N-9037 Tromsù, Norway M. Andersen á A.M. Hjelset á B. Gulliksen The University Courses on Svalbard, N-9170 Longyearbyen, Svalbard, Norway I. Gjertz Norwegian Polar Institute, P.O. Box 5072 Majorstua, N-0301 Oslo, Norway C. Lydersen á M. Andersen (&) Norwegian Polar Institute, N-9005 Tromsù, Norway e-mail: magnus.andersen@tromso.npolar.no, Fax: + 47-77606700