Life history traits of rare Antarctic dragonfishes from the Weddell Sea

The life history traits of bathydraconids, deep-living fishes distributed all around the Antarctic continent, are poorly known. In particular, very few data are available on the relatively rare genera Akarotaxis and Bathydraco. With the aim to fill this gap, sagittal otoliths and gonads were analysed to assess individual age and reproductive features of Akarotaxis nudiceps (Waite, 1916), Bathydraco macrolepis Boulenger 1907 and Bathydraco marri Norman, 1938 collected in the Weddell Sea. Based on the annual growth increment patterns, age estimates ranged between 6–11, 5–11 and 8–11 years for A. nudiceps, B. macrolepis and B. marri, respectively. Most of the gametogenetic processes could be described based on gonad histology for both sexes. Females shared the reproductive features commonly reported in notothenioids, such as group-synchronous ovary development and prolonged gametogenesis. Total fecundity estimates were comparable between the two species of Bathydraco (1500–2500 eggs/female), whereas that of Akarotaxis was one order of magnitude smaller (200–250 eggs/female). Consistently, the mean size of late vitellogenic oocytes showed an opposite trend, being 1.6–1.8 mm in Bathydraco and 2.2 mm in Akarotaxis.