Aggregation patterns in juvenile southern king crab Lithodes santolla (Molina, 1782): Are the aggregations related to moulting activity?

Abstract

The early life history of decapod species involves several stages and ontogeny-related shifts in habitat requirements and behaviour. Early publications have reported that, in the San Jorge Gulf (45–47°S), Argentina, juvenile southern king crab Lithodessantolla (Molina, 1782) (SKC) remain in rocky coastal habitats for at least three years, prior to their migration to soft bottoms. In this study, we analysed the gregarious behaviour of juvenile SKCs and its relation with moulting activity through the early ontogeny of the species. Different aggregation patterns were observed in SKC juveniles during sampling. These aggregation patterns were related to an increase in moulting activity. SKC 1+ and 2+ formed small groups of 7–31 juveniles in holes or cracks at shallower depths. A large aggregation was recorded in November 2014 associated with Macrocystis pyrifera forests. This aggregation involved advanced juveniles 3+, probably at the end of their stay in the coastal environment. Our results suggest that the aggregation of juvenile SKCs is related to high moulting activity and that differences in the aggregation patterns are related to ontogeny. The aggregation of advanced juveniles may reflect a (re)synchronous moult prior to a coordinated abandonment of the coastal environment.