Shoal of orange-spine unicornfish (Naso lituratus) moving over a coral reef. Every December and January this fish aggregates to spawn in shoals of hundreds or thousands of individuals. The shoal moves constantly to attempt to evade the predatory sharks in the area. This fish is also known as the orange-spined surgeonfish, naso tang or, in the local dialect, 'erangl'. Filmed off Palau, in the western Pacific Ocean.