Aspects of the biology of the Antarctic dragonfish Gerlachea australis (Notothenioidei: Bathydraconidae) in the Weddell Sea, Antarctica

The Antarctic dragonfish Gerlachea australis is one of the most common bathydraconid species within the fish community of the Filchner Depression in the Weddell Sea. Nevertheless, several biological aspects of this species remain poorly known. The aim of this study was to provide new data on its population structure in terms of size, sex and age through sagittal otolith readings, as well as some reproductive traits based on macroscopic and histological analyses of gonads. The sex ratio in the sampled population was 1:1, with males being significantly smaller than females. Both sexes attained maximum age estimates of 14 years. Based on a von Bertalanffy growth model, females showed a higher asymptotic length than males at a comparable growth rate, thus reaching a higher growth performance. The spawning season was spread over a relatively long period, lasting at least from late December through late February. The reproductive effort in terms of fecundity and egg size diameter was similar to that of other bathydraconids, ranging from 739 to 1260 eggs/female and 3.2 mm after hydration, respectively. The fish size at first spawning (TL50) was 18.5 and 22.5 cm in males and females, corresponding to 80% of their maximum size. G. australis exhibited a combination of life history traits found in other high-Antarctic notothenioids, such as long gametogenesis, large eggs associated with low fecundity, relatively rapid body growth until reaching a delayed sexual maturity, moderate longevity and maximum size, and overall low growth performance.