Aggregation of Humpback Red Snapper over crown-of-thorns

Humpback Red Snapper, aka Paddletail Snapper, often aggregate in large schools, staying completely stationary or drifting slowly along sloping reefs as one unit.
 
Scientific Name: Lutjanus gibbus
 
Under certain conditions periodic population explosions of crown-of-thorns starfish can occur on reefs, generating alarm due to the extensive damage they can unleash to the corals and the reef ecosystem.
 
Scientific Name: Acanthaster planci