Two things to note in the video, which is in HD and worth the full screen effect. First, there's an instant where the shark looks like it has some kind of brief spasm. A mackerel had shot up, fast as a bullet, and eaten one of the tiny fish gathered around the shark's nose. The shark reflexively tried to bite the mackerel, but the mackerel was way too fast.
The other thing to note is the aforementioned cloud of tiny fish around the shark's nose. These guys are ride-alongs, waiting for the shark's messy meal so they can snap up the table scraps. The shark seems to ignore them as they're too small and too quick to be worth trying to eat. This shark had a larger, black fish following around his dorsal fin in addition to the cloud of tinies at his nose.