Modified fin morphology in mackerel icefish (Champsocephalus gunnari) may indicate nesting behaviour

Monitoring reproductive traits in Southern Ocean species is challenging. Males in some channichthyids thicken the epithelium along their anal fins to aid nest construction. This study presents initial evidence that the only commercially harvested channichthyid, mackerel icefish (Champsocephalus gunnari), exhibits modifications to their anal fins, and that these features are ephemeral and possibly sexually dimorphic. The evidence presented may indicate nesting behaviour, although further work is necessary to validate this hypothesis. Confirming icefish nesting sites in the Scotia Sea could provide further support for the continued prohibition of bottom trawling.