Early life history traits of Dacodraco hunteri, a rare icefish collected in the Ross Sea, Southern Ocean

The composition of the larval fish assemblages in the Ross Sea is relatively well known, especially in the western sector. One of the most abundant icefish is Dacodraco hunteri (Channichthyidae), although it is considered a rare species as an adult. In the present study, we aimed at assessing aspects of the early life history of this species, such as age, hatching period, growth rate and feeding habits, and comparing samples collected in the eastern and western sectors of the Ross Sea. Individual age estimates were obtained by otolith microincrement counts and body growth was described by an exponential model. Diet composition was inferred from stomach content analysis. Fish samples consisted of yolk-sac and preflexion larval stages of development, with an estimated age range of 49-80 days. Growth rates were similar in both sectors of the Ross Sea ranging between 0.18 and 0.19 mm/day, which corresponded to a daily increase of 1.07-1.08% of body size. Larval hatching took place over a relatively short period (November), at a mean size of 8.2-8.7 mm notochord length. Larval stages of Pleuragramma antarcticum were the only prey items found in the stomachs, though with different frequency of occurrence in the eastern (13%) and western sectors (38%) of the Ross Sea. Consistent with previous data, the early life cycle of D. hunteri was characterized by relatively small larvae hatching in summer and overwintering juveniles with a specialized diet of P. antarcticum. D. hunteri are likely to be one of the main consumers of P. antarcticum within the pelagic realm.