This is an amazing and beautiful thing. Photos and video of sailfish cooperating to herd schools of sardine.
“The hunt seems almost mammalian. Sailfish—which often travel in loose groups—clearly join forces. Males and females alike circle the prey, pushing the school into tighter formation, and taking a few bites in turn. Each forward rush is punctuated by a startling flare of the dorsal fin, which more than doubles the hunter’s profile . . . The sardines, too, work in concert. Detecting each other’s proximity and movement, they shift in synchrony, each fish both leader and follower. The fish mass slides like a drop of mercury, mesmerizing, with a shimmer that may help to confuse predators . . .”
Read more at National Geographic.