Anemonefishes are an iconic and diverse group that is reliant on a critical habitat (anemones) which has declined significantly in recent years – primarily due to mass bleaching events. Disenfranchised anemonefishes may relocate to already colonised anemones after their host dies and the available habitat is limited. Sometimes multiple species may end up coexisting together in what are called ‘cohabiting’ or ‘mixed-species’ groups. Aggressive interactions normally prevent different anemonefish species from cohabiting – thus, the observation of stable cohabiting groups indicates a decrease in the territorial aggression that usually keeps species separate. Therefore, it is of interest to investigate the mechanisms enabling these groups to form.
The overarching objective of this behavioural study was to explore the ecological and behavioural factors underlying the changes in territorial aggression seen in cohabiting anemonefish groups. It focuses on two species known to form cohabiting groups in colonies of the bubble-tip anemone (Entacmaea quadricolor); the Great Barrier Reef anemonefish (Amphiprion akindynos) and the Red-and-Black anemonefish (Amphiprion melanopus). Territorial defence scenarios were simulated in aquaria, where the aggression of resident anemonefishes towards conspecific and heterospecific intruders were compared. I will also present the results of field surveys characterizing cohabitation in anemonefishes around Lizard Island.