I didn't make it out Saturday but I've experienced this before. At the North End as well as 37th St., I've seen them in the middle of summer too. I try to keep my distance. It's cool to watch the dolphin corral them but a little freaky when you get surrounded.
But why would it be less safe if there's dolphin around? I've heard of people getting raped by dolphins, but I imagine that only happens to dumb college girls on spring break.
It's easy to tell a Dolphin from a shark, they act completely different when feeding not to mention Dolphins breathe and have horizontal tail fins. Usually if you see a school of sharks attacking bait fish you will only see their tail fins thrashing around and rarely see their dorsals--it's opposite with Dolphins.
Also, it's common knowledge that Dolphins are more of an apex predator than sharks. Sharks will avoid a pod of Dolphins at all costs because 9 times out of 9 they will wind up dead from busted gills. I have witnessed this in the lineup at WB, CB and OIB multiple times--always resulting in a dead shark washing up on the shore. I'm sure it's not 100% but it's close enough for me.
As for the bait fish, I agree it's probably Menhaden--especially if the school is about the size of a football field. One thing in our area of the coast (SE NC) the push of Menhaden brings big ass Cobia (70 - 100+ lbs) into the shallows near the inlets. Cobia look almost exactly like sharks but behave completely different. They are very curious and love hanging out around things floating in the water--like surfers and boats, so they can often be mistaken for a shark. The way we catch cobia offshore is to get over a reef, spray menhaden oil in the water to create a slick and "chum" by throwing live menhaden overboard. We have jigging rods with big bucktails tipped with either menhaden or blue crab that we toss out when we see a big brown blob making its way to the boat. Usually it's a cobia, but it can be any various species of shark too, either way it's a good fight and Cobia is mighty tasty.
It is true that dolphins Generally detour sharks because they travel in pods. When a shark comes into the shallows they are generally riding solo.
It is also true that they eat the same things, in the same places. There is almost ALWAYS a fin to be seen in frisco too. That place is bad, supposedly they even have a population of hammerheads that hang out in the cove.
I was surfing on the south side of the Rodanthe Pier one summer morning. There was a lot of marine activity so I made sure to not contribute to the buffet (laying prone between waves). About 10 minutes in I hear a bunch of commotion coming from the pier. No big deal. I took a wave towards the pier and then I'm like WTF is that? is that a ... what? Some fisherman snagged a 5 or 6 foot bullshark and the genius attepted to try to reel it up to the pier. Doesn't take a physicist to decide that isn't happening... Anyways, when I'm about 20 yards from it he starts yelling to get out of the water because he is cutting the line. I have surfed with sharks before, but this f*ckng thing was thrashing and splashing and now heading right for me. I froze and sat still and knew it was about to go down. It must have swam right under me and headed out to sea. Yeah, that's my best shark story.