Greasy Grouper

Large solitary individuals of this widespread IndoPacific grouper have colonised the wreck's hold and upper superstructure, where they sit in ambush for passing reef fish and squid. They are protogynous hermaphrodites — all born female and some transitioning to male later in life — and the biggest individuals on the Mercury are likely decades old. As apex predators on the wreck they regulate the populations of mid-sized reef fish that might otherwise overgraze the coral communities growing on the hull.