After working with groupers and sea trout during my post doc, I thought this blogpost on the National Geographic site highlighting a recent paper (link here) was interesting.
Groupers use gestures to get morays eel to help them hunt. The groupers are good at catching prey in the open water, whereas the moray eels are good at flushing the prey out of crevices. Apparently the sea trout do this with octopus!
Here is one of a grouper