Triggerfish (Balistidae) All species have a deep flattened body, and a small but strong mouth. Triggerfish have a spine at the top of their head, which becomes erect when threatened, and is able to wedge the fish in crevices if it is being attacked. During their breeding season (December to January), Triggerfish become particularly aggressive and will chase and bite snorkellers if they are too close to their nests. The common Piccasso or White Barred Triggerfish (Rhinecanthus aculaeatus) has a distinctive blue mask across the eyes and feeds on a variety of things, including algae, invertebrates and detritus. Often reaches lengths of 25cm.