Giant grouper gets his face cleaned by brave little shrimp

Nassau groupers are beautiful and highly intelligent fish. They are plentiful in the Cayman Islands and elsewhere in the Caribbean. One of the top predators, they keep the reef healthy by preying on the weak and dying fish. Recently, they have been found to possess enough intelligence that they are actually able to communicate with moray eels and team up to hunt cooperatively. Both the grouper and the eel benefit from the assistance of the other. Groupers also possess enough intelligence to understand when scuba divers have spears for killing lion fish, an invasive and destructive fish. The groupers not only follow the divers to get a free meal, but they also swim ahead, looking in crevices for the lion fish. They will signal the divers when they see one.

This grouper has found a chunk of coral where wrasses and cleaner shrimp are waiting. These collections of fish and shrimp are referred to as "cleaning stations" and groupers will open their mouths and float in a slightly upright position to signal the other species that they are wanting cleaned. In return, the wrasses and shrimp get to eat the small parasites and dead skin that cling to the grouper. This is an age old partnership that is mutually beneficial to both species. What is surprising is that the smaller animals instinctively know that they can trust the grouper not to inhale and eat them. The grouper also knows that doing so would break the trust and would leave him without the assistance that he relies on.

Groupers in the Cayman Islands have been declining in recent years and scientists have gone to great lengths to determine why. They attached devices implanted on their sides that have color coded surfaces to identify them and track their movements and migration during breeding cycles. The devices will also transmit data that can be detected if the groupers come close enough to special sensors. This also tells the scientists a great deal about where the groupers are spending their time.

The more we learn about species like the grouper, and about their mysterious behavior, the more we understand that we still have a lot to learn. The undersea world is mysterious and delicate and the relationships between the species is far more complex than we ever imagined.