Swallowtail sea perch

This is the most tropical-looking fish in Maltese water and the one that makes deep dives memorable. The body is short, deep and compressed, coloured a vivid rose pink to orange-red with three fine yellow lines radiating back across the cheek from the eye and snout. The tail is deeply forked into two long trailing streamers, which is where the English name comes from, and the pelvic fins are extraordinarily long, bright yellow, and held down and forward like a pair of banners. Dominant males carry the longest fins of all and redden strongly in the breeding season. Fish are usually 12 to 18 cm and reach about 27 cm.

Around the Maltese islands they live from roughly 30 metres down, on shaded rock, cave mouths, overhangs and deep coralligenous reef, and they are one of the classic sights of Gozo's Blue Hole and inland sea tunnel, the outer Dwejra walls, Ras il-Ħobż, Comino's deeper drop-offs and the deeper Maltese wrecks. They shelter in the shade by day and drift out to pick zooplankton from the current, hanging in loose aggregations that face into the flow.

Anthias are protogynous hermaphrodites: almost all start as females, and when a dominant male is lost the largest female changes sex and takes over the harem within days. Because they live in shade and colour is stripped out by depth, most divers see them as small grey shapes until a torch is turned on, at which point the wall lights up pink.